DEV: a shared resource utility added

include/utl/container/deque.h

@@ -0,0 +1,225 @@
+/*!
+ * \file container/deque.h
+ * \brief
+ *      A statically allocated deque based on a ring buffer.
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_container_deque_h__
+#define utl_container_deque_h__
+
+#include <utl/core/impl.h>
+#include <utl/container/ring_iterator.h>
+#include <utl/container/range.h>
+#include <array>
+#include <atomic>
+
+namespace utl {
+
+/*!
+ * \class deque
+ * \brief
+ *      A statically allocated deque based on a ring buffer
+ *
+ * The deque uses two ring_iterators one for the front and one for the rear. The iterators
+ * are pointing to the next available spot, not on the last inserted spot. This way at the
+ * initialization the iterators wont "pretend" to point to a valid item .
+ *
+ * We use a ring buffer of size \c N+1. We start the front iterator at the last location of the buffer
+ * and the rear on the first. This way when the queue is full the iterators are pointing to the same location.
+ *
+ * \tparam Data_t       The char-like queued item type. Usually \c char
+ * \tparam N            The size of deque
+ * \tparam SemiAtomic   True for semi-atomic operation. In that case the \c ring_iterator is also atomic.
+ * \note
+ *      SemiAtomic means it is safe to access different ends from different threads. For example one thread can
+ *      push only from front and another can pop from back to implement a queue.
+ */
+template <typename Data_t, size_t N, bool SemiAtomic =false>
+class deque {
+    public:
+        // meta-identity type
+        using type              = deque<Data_t, N>;
+        using buffer_t          = std::array<Data_t, N+1>;  // We need N+1 spaces ring buffer for N spaces deque
+        using iterator_t        = ring_iterator<Data_t*, N+1, SemiAtomic>;
+        using range_t           = range<iterator_t>;
+
+        // STL
+        using value_type        = Data_t;
+        using reference         = Data_t&;
+        using const_reference   = const Data_t&;
+        using pointer           = Data_t*;
+        using const_pointer     = const Data_t*;
+        using iterator          = iterator_t;
+        using const_iterator    = const iterator_t;
+        using reverse_iterator  = std::reverse_iterator<iterator>;
+        using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+
+    //! \name Constructor / Destructor
+    //! @{
+    public:
+        //! Default constructor
+        constexpr deque () noexcept :
+            data_{},
+            f{data_.data(), N},
+            r{data_.data()} {
+                if constexpr (SemiAtomic)
+                    std::atomic_thread_fence(std::memory_order_release);
+            }
+
+        //! fill contructor
+        constexpr deque(const Data_t& value) noexcept {
+            data_.fill(value);
+            f = iterator(data_.data(), N);
+            r = iterator(data_.data(), N);
+            if constexpr (SemiAtomic)
+                std::atomic_thread_fence(std::memory_order_release);
+        }
+
+        //! Initializer list contructor
+        template <typename ...It>
+        constexpr deque(It&& ...it) noexcept :
+            data_{{std::forward<It>(it)...}},
+            f(data_.data(), N),
+            r(data_.data(), sizeof...(It)) {
+                if constexpr (SemiAtomic)
+                    std::atomic_thread_fence(std::memory_order_release);
+            }
+
+        deque(const deque&) = delete;                   //!< No copies
+        deque& operator= (const deque&) = delete;       //!< No copy assignments
+        ~deque () = default;                            //!< default destructor
+    //! @}
+
+    //! \name Iterators
+    //! @{
+    public:
+        constexpr iterator begin() noexcept               { iterator ret = f; return ++ret; }
+        constexpr const_iterator begin() const noexcept   { iterator ret = f; return ++ret; }
+        constexpr const_iterator cbegin() const noexcept  { iterator ret = f; return ++ret; }
+
+        constexpr iterator end() noexcept                 { return r; }
+        constexpr const_iterator end() const noexcept     { return r; }
+        constexpr const_iterator cend() const noexcept    { return r; }
+
+        constexpr reverse_iterator rbegin() noexcept              { return r; }
+        constexpr const_reverse_iterator rbegin() const noexcept  { return r; }
+        constexpr const_reverse_iterator crbegin() const noexcept { return r; }
+
+        constexpr reverse_iterator rend() noexcept                { reverse_iterator ret = f; return ++ret; }
+        constexpr const_reverse_iterator rend() const noexcept    { reverse_iterator ret = f; return ++ret; }
+        constexpr const_reverse_iterator crend() const noexcept   { reverse_iterator ret = f; return ++ret; }
+    //! @}
+
+    //! \name Capacity
+    //! @{
+    public:
+        //! \return The size of the deque. The items currently in queue.
+        constexpr size_t size() noexcept {
+            return r - (f +1);
+        }
+        constexpr size_t size() const noexcept {
+            return r - (f +1);
+        }
+        //! \return The maximum size of the deque. The items the queue can hold.
+        constexpr size_t max_size() noexcept { return N; }
+        //! \return The capacity of the deque. The items the queue can hold.
+        constexpr size_t capacity() noexcept { return N; }
+        //! \return True if the deque is empty
+        constexpr bool   empty()    noexcept { return size() == 0 ? true : false; }
+        //! \return True if the deque is full
+        constexpr bool   full()     noexcept { return size() == N ? true : false; }
+
+    //! @}
+
+    //! \name Member access
+    //! @{
+    public:
+        //! \brief  Clears-empty the deque and return it to init state, without
+        //!         really deleting the contents.
+        constexpr void clear() noexcept {
+            f = iterator_t(data_.data(), N);
+            r = iterator_t(data_.data());
+            if constexpr (SemiAtomic)
+                std::atomic_thread_fence(std::memory_order_release);
+        }
+        //! \brief      Push an item in the front of the deque
+        //! \param it   The item to push
+        constexpr void push_front (const Data_t& it) noexcept {
+            if (full())     return;
+            *f = it;
+            --f;        // keep this separate for thread safety
+        }
+        //! \brief      Push an item in the back of the deque
+        //! \param it   The item to push
+        constexpr void push_back (const Data_t& it) noexcept {
+            if (full())     return;
+            *r = it;
+            ++r;        // keep this separate for thread safety
+        }
+        //! \brief      Extract an item from the front of the deque and remove it from the deque
+        //! \param it   The item to push
+        constexpr Data_t pop_front () noexcept {
+            if (empty())    return Data_t{};
+            return *++f;
+        }
+        //! \brief      Extract an item from the back of the deque and remove it from the deque
+        //! \param it   The item to push
+        constexpr Data_t pop_back () noexcept {
+            if (empty())    return Data_t{};
+            return *--r;
+        }
+
+        //! \brief      Get a reference to the item in the front of the deque without extracting it.
+        //! \return     Reference to the item
+        constexpr Data_t& front() noexcept { iterator_t it = f; return *++it; }
+        constexpr const Data_t& front() const noexcept { iterator_t it = f; return *++it; }
+
+        //! \brief      Get a reference to the item in the front of the deque without extracting it.
+        //! \return     Reference to the item
+        constexpr Data_t& back() noexcept { iterator_t it = r; return *--it; }
+        constexpr const Data_t& back() const noexcept { iterator_t it = r; return *--it; }
+
+        //! \brief      Get a pointer to the begin of the items on the deque
+        //! \return
+        constexpr Data_t* data() noexcept { return &front(); }
+        constexpr const Data_t* data() const noexcept { return &front(); }
+
+        //! \brief      Get a range for the data in queue
+        //! \return     A begin-end iterator pair struct
+        constexpr range_t contents () noexcept { iterator_t b = f; return {++b, r}; }
+        constexpr const range_t contents () const noexcept { iterator_t b = f; return {++b, r}; }
+
+    //! @}
+    private:
+        buffer_t    data_{};            //!< The statically allocated buffer
+        iterator_t  f{data_.data(), N}; //!< A ring iterator for the front (points to the next available location)
+        iterator_t  r{data_.data()};    //!< A ring iterator for the rear (points to the next available location).
+};
+
+} // namespace utl
+
+#endif /* utl_container_deque_h__ */

include/utl/container/edeque.h

@@ -0,0 +1,299 @@
+/*!
+ * \file container/edeque.h
+ * \brief
+ *      A deque with event based callables
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_container_edeque_h__
+#define utl_container_edeque_h__
+
+#include <utl/core/impl.h>
+#include <utl/container/deque.h>
+
+#include <functional>
+#include <utility>
+#include <type_traits>
+
+namespace utl {
+
+/*!
+ * \class edeque
+ * \brief
+ *      A statically allocated deque with size and data matching event based callables.
+ *
+ * The edeque inherits deque and provide the callable functionality as a wrapper.
+ *
+ * There are two types of events.
+ *  - Size based events, which are cleared as soon as they served. These events are checked
+ *    every time the deque change its size. If the criteria match we call the callable of type
+ *    \c Fn
+ *  - Data based events, which are permanently. These events are checked every time an item is
+ *  pushed or popped from the deque. If the criteria match we call call the callable of type
+ *    \c Fn
+ *
+ * \tparam Data_t       The char-like queued item type. Usually \c char
+ * \tparam N            The size of edeque
+ * \tparam SemiAtomic   True for semi-atomic operation. In that case the \c ring_iterator is also atomic.
+ * \tparam Fn           The type of Callable
+ * \note
+ *      SemiAtomic means it is safe to access different ends from different threads. For example one thread can
+ *      push only from front and another can pop from back to implement a queue.
+ */
+template <typename Data_t, size_t N, bool SemiAtomic =false, typename Fn = std::function<void()>>
+class edeque : public deque<Data_t, N, SemiAtomic> {
+    public:
+        // meta-identity types
+        using type                  = edeque<Data_t, N, SemiAtomic, Fn>;
+        using base_type             = deque<Data_t, N, SemiAtomic>;
+        using callable_t            = Fn;
+        using range_t               = typename base_type::range_t;
+
+        // STL
+        using value_type            = typename base_type::value_type;
+        using reference             = typename base_type::reference;
+        using const_reference       = typename base_type::const_reference;
+        using pointer               = typename base_type::pointer;
+        using const_pointer         = typename base_type::const_pointer;
+        using iterator              = typename base_type::iterator;
+        using const_iterator        = typename base_type::const_iterator;
+        using reverse_iterator      = typename base_type::reverse_iterator;
+        using const_reverse_iterator= typename base_type::const_reverse_iterator;
+
+    //! \name Public types
+    //! @{
+    public:
+        //! \enum match_mode
+        //! The mode of match operation
+        enum class match_mode { SIZE, DATA };
+        //! \enum size_match
+        //! The type of matching for size based match
+        enum class size_match { DISABLED =0, EQ, NE, LT, LE, GT, GE };
+        //! \enum data_match
+        //! The type of matching for data based match
+        enum class data_match { DISABLED =0, MATCH_PUSH, MATCH_POP, MISMATCH_PUSH, MISMATCH_POP};
+
+//        TODO: trigger mode for one-shot or repeated functionality
+//        enum class trigger_mode { ONE_SHOT, REPEATED };
+
+        //! \struct size_trigger
+        //! Size trigger data type
+        struct size_trigger {
+            size_match      type;
+            size_t          size;
+        };
+        //! \struct data_trigger
+        //! Data trigger data type
+        struct data_trigger {
+            data_match      type;
+            Data_t          value;
+        };
+        //! \union trigger
+        //! \brief
+        //!     A union for the common types.
+        //! There is only one mode. Either "size" with \ref size_match type and a size to match,
+        //! or "data" with \ref data_match type and a value to match
+        union trigger {
+            size_trigger    tsize;
+            data_trigger    tdata;
+        };
+    //! @}
+
+    //! \name Constructor / Destructor
+    //! @{
+    public:
+        //! Default constructor
+        constexpr edeque () noexcept :
+            base_type() { }
+
+        //! Size trigger constructor
+        constexpr edeque (size_match match, size_t size, callable_t&& fn) noexcept :
+            base_type(),
+            mode_{match_mode::SIZE},
+            callback_{std::forward<callable_t>(fn)} {
+            trigger_.tsize.type = match;
+            trigger_.tsize.size = size;
+        }
+        //! Data trigger constructor
+        constexpr edeque (data_match match, Data_t value, callable_t&& fn) noexcept :
+            base_type(),
+            mode_{match_mode::DATA},
+            callback_{std::forward<callable_t>(fn)} {
+            trigger_.tdata.type = match;
+            trigger_.tdata.value = value;
+        }
+    //! @}
+
+    //! \name Public interface
+    //! @{
+
+        //! \brief
+        //!     Manually checks the size trigger and calls it we have match.
+        //! \return     True if the callable has called.
+        bool check_trigger () noexcept {
+            return check_trigger_size_();
+        }
+
+        //! \brief
+        //!     Manually set (or alters) the \c size trigger. This function does not fire the
+        //! \ref check_trigger()
+        //! \param match    The match type
+        //! \param size     The size for with we check against
+        //! \param fn       The callable to call on match
+        void set_trigger (size_match match, size_t size, callable_t&& fn) noexcept {
+            mode_               = match_mode::SIZE;
+            trigger_.tsize.type = match;
+            trigger_.tsize.size = size;
+            callback_           = std::forward<callable_t>(fn);
+        }
+
+        //! \brief
+        //!     Manually set (or alters) the \c data trigger. This function does not fire the
+        //! \ref check_trigger()
+        //! \param match    The match type
+        //! \param value    The value for with we check against
+        //! \param fn       The callable to call on match
+        void set_trigger (data_match match, Data_t value, callable_t&& fn) noexcept {
+            mode_               = match_mode::DATA;
+            trigger_.tdata.type = match;
+            trigger_.tdata.value= value;
+            callback_           = std::forward<callable_t>(fn);
+        }
+
+        //! \brief Manually clears the trigger
+        void clear_trigger () noexcept {
+            mode_       = match_mode{};
+            trigger_    = trigger{};
+            callback_   = callable_t{};
+        }
+    //! @}
+
+    //!  \name Base class uses and overwrites
+    //! @{
+        void push_front (const Data_t& it) noexcept {
+            base_type::push_front(it);
+            check_trigger_push_async_(it);
+        }
+        void push_back (const Data_t& it) noexcept {
+            base_type::push_back(it);
+            check_trigger_push_async_(it);
+        }
+        Data_t pop_front () noexcept {
+            Data_t t = base_type::pop_front();
+            check_trigger_pop_async_(t);
+            return t;
+        }
+        Data_t pop_back () noexcept {
+            Data_t t = base_type::pop_back();
+            check_trigger_pop_async_(t);
+            return t;
+        }
+    //! @}
+
+    //! \name Private functionality
+    //! @{
+    private:
+        //! \brief
+        //!     Manually checks the size trigger and calls it we have match.
+        //! \return     True if the callable has called.
+        bool check_trigger_size_ () {
+            bool match;
+            switch (trigger_.tsize.type) {
+                default:
+                case size_match::DISABLED:  match = false; break;
+                case size_match::EQ:        match = (base_type::size() == trigger_.tsize.size); break;
+                case size_match::NE:        match = (base_type::size() != trigger_.tsize.size); break;
+                case size_match::LT:        match = (base_type::size() <  trigger_.tsize.size); break;
+                case size_match::LE:        match = (base_type::size() <= trigger_.tsize.size); break;
+                case size_match::GT:        match = (base_type::size() >  trigger_.tsize.size); break;
+                case size_match::GE:        match = (base_type::size() >= trigger_.tsize.size); break;
+            }
+            if (match) {
+                callback_();
+                clear_trigger();
+            }
+            return match;
+        }
+
+        //! \brief
+        //!     Manually checks the data trigger on push and calls it we have match.
+        //! \param  it  The item to check against
+        //! \return     True if the callable has called.
+        bool check_trigger_push_value_ (const Data_t& it) {
+            bool match;
+            switch (trigger_.tdata.type) {
+                default:
+                case data_match::DISABLED:      match = false;  break;
+                case data_match::MATCH_PUSH:    match = (it == trigger_.tdata.value); break;
+                case data_match::MISMATCH_PUSH: match = (it != trigger_.tdata.value); break;
+            }
+            if (match)
+                callback_();
+            return match;
+        }
+
+        //! \brief
+        //!     Manually checks the data trigger on pop and calls it we have match.
+        //! \param  it  The item to check against
+        //! \return     True if the callable has called.
+        bool check_trigger_pop_value_ (const Data_t& it) {
+            bool match;
+            switch (trigger_.tdata.type) {
+                default:
+                case data_match::DISABLED:      match = false;  break;
+                case data_match::MATCH_POP:     match = (it == trigger_.tdata.value); break;
+                case data_match::MISMATCH_POP:  match = (it != trigger_.tdata.value); break;
+            }
+            if (match)
+                callback_();
+            return match;
+        }
+
+        //! Wrapper for both triggers at push
+        bool check_trigger_push_async_ (const Data_t& it) {
+            switch (mode_) {
+                default:
+                case match_mode::SIZE:  return check_trigger_size_();
+                case match_mode::DATA:  return check_trigger_push_value_(it);
+            }
+        }
+        //! Wrapper for both triggers at pop
+        bool check_trigger_pop_async_ (const Data_t& it) {
+            switch (mode_) {
+                default:
+                case match_mode::SIZE:  return check_trigger_size_();
+                case match_mode::DATA:  return check_trigger_pop_value_(it);
+            }
+        }
+    //! @}
+    private:
+        match_mode  mode_{};
+        trigger     trigger_{};
+        callable_t  callback_{};
+};
+} // namespace utl
+
+#endif /* utl_container_edeque_h__ */

include/utl/container/equeue.h

@@ -0,0 +1,146 @@
+/*!
+ * \file container/equeue.h
+ * \brief
+ *      A queue with event based callables based on edeque.
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_container_equeue_h__
+#define utl_container_equeue_h__
+
+#include <utl/core/impl.h>
+#include <utl/container/edeque.h>
+
+namespace utl {
+
+/*!
+ * \class equeue
+ * \brief
+ *      A statically allocated queue based on edeque with size and data matching
+ *      event based callables.
+ *
+ * We use the \ref edeque::push_back() and \ref edeque::pop_front() pair from edeque's
+ * functionality, so at the \c push the increment performed after the insertion.
+ * Similarly at the \c pop the decrement performed before the exctraction. This way also
+ * the \ref edeque::front() and \ref edeque::back() stay the same ;)
+ *
+ * We also provide stream operators.
+ *
+ * \tparam Data_t       The char-like queued item type. Usually \c char
+ * \tparam N            The size of edeque
+ * \tparam SemiAtomic   True for semi-atomic operation. In that case the \c ring_iterator is also atomic.
+ * \tparam Fn           The type of Callable
+ * \note
+ *      SemiAtomic means it is safe to for one thread to  push only from front and another can pop.
+ */
+template <typename Data_t, size_t N, bool SemiAtomic =false, typename Fn = std::function<void()>>
+class equeue : public edeque<Data_t, N, SemiAtomic, Fn> {
+    public:
+        // meta-identity types
+        using equeue_t              = equeue<Data_t, N, SemiAtomic, Fn>;
+        using base_type             = edeque<Data_t, N, SemiAtomic, Fn>;
+        using range_t               = typename base_type::range_t;
+
+        // STL
+        using value_type            = typename base_type::value_type;
+        using reference             = typename base_type::reference;
+        using const_reference       = typename base_type::const_reference;
+        using pointer               = typename base_type::pointer;
+        using const_pointer         = typename base_type::const_pointer;
+        using iterator              = typename base_type::iterator;
+        using const_iterator        = typename base_type::const_iterator;
+        using reverse_iterator      = typename base_type::reverse_iterator;
+        using const_reverse_iterator= typename base_type::const_reverse_iterator;
+
+    //! \name Constructor / Destructor
+    //! @{
+    public:
+        //! Default constructor
+        constexpr equeue () noexcept : base_type() { }
+
+        //! Forward constructor
+        template <typename ...It>
+        constexpr equeue(It&& ...it) noexcept : base_type(std::forward<It>(it)...) { }
+
+    //! @}
+
+    //! \name Member access
+    //! @{
+    public:
+        //! \brief      Push an item in the back of the queue
+        //! \param it   The item to push
+        void push (const Data_t& it) noexcept {
+            base_type::push_back(it);
+        }
+
+        //! \brief      Extract an item from the front of the queue and remove it from the queue
+        //! \param it   The item to push
+        Data_t pop () noexcept {
+            return base_type::pop_front();
+        }
+
+        //! \brief      Push an item in the back of the queue
+        //! \param it   The item to push
+        equeue_t& operator<< (const Data_t& it) noexcept {
+            push(it);
+            return *this;
+        }
+
+        //! \brief      Push an item in the back of the queue
+        //! \param it   The item to push
+        equeue_t& operator>> (Data_t& it) noexcept {
+            it = pop();
+            return *this;
+        }
+
+    //! @}
+
+};
+
+/*!
+ * \brief
+ *      Pop an item from the front of the queue.
+ *
+ *  This definition enables the "data << equeue" syntax for pop operation
+ *
+ *  \tparam Data_t      The char-like queued item type. Usually \c char
+ *  \tparam N           The size of queue
+ *  \tparam SemiAtomic  True for semi-atomic operation. In that case the \c ring_iterator is also atomic.
+ *  \tparam Fn          The type of Callable
+ *
+ *  \param it       The item to write to
+ *  \param q        The queue to read from
+ *  \return         Reference to the returned item
+ */
+template <typename Data_t, size_t N, bool SemiAtomic =false, typename Fn = std::function<void()>>
+Data_t& operator<< (Data_t& it, equeue<Data_t, N, SemiAtomic, Fn>& q) noexcept {
+    it = q.pop();
+    return it;
+}
+
+} // namespace utl
+
+#endif /* utl_container_equeue_h__ */

include/utl/container/queue.h

@@ -0,0 +1,144 @@
+/*!
+ * \file container/queue.h
+ * \brief
+ *      A statically allocated queue based on deque.
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_container_queue_h__
+#define utl_container_queue_h__
+
+#include <utl/core/impl.h>
+#include <utl/container/deque.h>
+
+namespace utl {
+
+/*!
+ * \class queue
+ * \brief
+ *      A statically allocated queue based on deque.
+ *
+ * We use the \ref deque::push_back() and \ref deque::pop_front() pair from deque's
+ * functionality, so at the \c push the increment performed after the insertion.
+ * Similarly at the \c pop the decrement performed before the exctraction. This way also
+ * the \ref deque::front() and \ref deque::back() stay the same ;)
+ *
+ * We also provide stream operators.
+ *
+ * \tparam Data_t       The char-like queued item type. Usually \c char
+ * \tparam N            The size of queue
+ * \tparam SemiAtomic   True for semi-atomic operation. In that case the \c ring_iterator is also atomic.
+ * \note
+ *      SemiAtomic means it is safe to for one thread to  push only from front and another can pop.
+ */
+template <typename Data_t, size_t N, bool SemiAtomic =false>
+class queue : public deque<Data_t, N, SemiAtomic> {
+    public:
+        // meta-identity types
+        using queue_t               = queue<Data_t, N, SemiAtomic>;
+        using base_type             = deque<Data_t, N, SemiAtomic>;
+        using range_t               = typename base_type::range_t;
+
+        // STL
+        using value_type            = typename base_type::value_type;
+        using reference             = typename base_type::reference;
+        using const_reference       = typename base_type::const_reference;
+        using pointer               = typename base_type::pointer;
+        using const_pointer         = typename base_type::const_pointer;
+        using iterator              = typename base_type::iterator;
+        using const_iterator        = typename base_type::const_iterator;
+        using reverse_iterator      = typename base_type::reverse_iterator;
+        using const_reverse_iterator= typename base_type::const_reverse_iterator;
+
+    //! \name Constructor / Destructor
+    //! @{
+    public:
+        //! Default constructor
+        constexpr queue () noexcept : base_type() { }
+
+        //! fill contructor
+        constexpr queue(const Data_t& value) noexcept : base_type(value) { }
+
+        //! Initializer list contructor
+        template <typename ...It>
+        constexpr queue(It&& ...it) noexcept : base_type(std::forward<It>(it)...) { }
+
+    //! @}
+
+    //! \name Member access
+    //! @{
+    public:
+        //! \brief      Push an item in the back of the queue
+        //! \param it   The item to push
+        constexpr void push (const Data_t& it) noexcept {
+            base_type::push_back(it);
+        }
+
+        //! \brief      Extract an item from the front of the queue and remove it from the queue
+        //! \param it   The item to push
+        constexpr Data_t pop () noexcept {
+            return base_type::pop_front();
+        }
+
+        //! \brief      Push an item in the back of the queue
+        //! \param it   The item to push
+        constexpr queue_t& operator<< (const Data_t& it) noexcept {
+            push(it);
+            return *this;
+        }
+
+        //! \brief      Pop an item from the front of the queue
+        //! \param it   The item to write to
+        constexpr queue_t& operator>> (Data_t& it) noexcept {
+            it = pop();
+            return *this;
+        }
+    //! @}
+};
+
+/*!
+ * \brief
+ *      Pop an item from the front of the queue.
+ *
+ *  This definition enables the "data << queue" syntax for pop operation
+ *
+ *  \tparam Data_t      The char-like queued item type. Usually \c char
+ *  \tparam N           The size of queue
+ *  \tparam SemiAtomic  True for semi-atomic operation. In that case the \c ring_iterator is also atomic.
+ *
+ *  \param it       The item to write to
+ *  \param q        The queue to read from
+ *  \return         Reference to the returned item
+ */
+template <typename Data_t, size_t N, bool SemiAtomic =false>
+constexpr Data_t& operator<< (Data_t& it, queue<Data_t, N, SemiAtomic>& q) noexcept {
+    it = q.pop();
+    return it;
+}
+
+} // namespace utl
+
+#endif /* utl_container_queue_h__ */

include/utl/container/range.h

@@ -0,0 +1,64 @@
+/*!
+ * \file container/range.h
+ * \brief
+ *      A plain definition of a range struct with agregate initialization
+ *      and begin-end pairs.
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_container_range_h__
+#define utl_container_range_h__
+
+#include <utl/core/impl.h>
+
+namespace utl {
+
+/*!
+ * \brief
+ *  A plain definition of a range struct with begin-end pairs.
+ *
+ * \tparam Iter_t   The iterator type of the range
+ */
+template <typename Iter_t>
+struct range {
+    Iter_t  b{}, e{};
+
+//    range () = default;
+//    range (const Iter_t& first, const Iter_t& last) noexcept :
+//        b(first), e(last) { }
+//    range (Iter_t first, Iter_t last) noexcept :
+//        b(first), e(last) { }
+
+    Iter_t begin()              { return b; }
+    const Iter_t begin() const  { return b; }
+    const Iter_t cbegin() const { return b; }
+    Iter_t end()                { return e; }
+    const Iter_t end() const    { return e; }
+    const Iter_t cend() const   { return e; }
+};
+
+} // namespace utl;
+#endif /* utl_container_range_h__ */

include/utl/container/ring_iterator.h

@@ -0,0 +1,453 @@
+/*!
+ * \file container/ring_iterator.h
+ * \brief
+ *      A ring/circular iterator.
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_container_ring_iterator_h__
+#define utl_container_ring_iterator_h__
+
+#include <utl/core/impl.h>
+
+#include <iterator>
+#include <type_traits>
+#include <atomic>
+
+namespace utl {
+
+template<typename Iter_t, size_t N, bool Atomic=false>
+class ring_iterator {
+    //! \name STL iterator traits "forwarding"
+    //! @{
+    protected:
+        using traits_type = std::iterator_traits<Iter_t>;
+
+    public:
+        using iterator_type     = Iter_t;
+        using iterator_category = typename traits_type::iterator_category;
+        using value_type        = typename traits_type::value_type;
+        using difference_type   = typename traits_type::difference_type;
+        using reference         = typename traits_type::reference;
+        using pointer           = typename traits_type::pointer;
+    //! @}
+
+
+    //! \name Constructor / Destructor
+    //! @{
+    public:
+        constexpr ring_iterator(const Iter_t base =nullptr) noexcept :
+            base_(base), iter_(base) { }
+
+        constexpr ring_iterator(const Iter_t base, size_t elem) noexcept :
+            base_(base), iter_(base + elem) { }
+
+        constexpr ring_iterator(const ring_iterator& it) noexcept :
+            base_(it.base_), iter_(it.iter_) { }
+
+        constexpr ring_iterator& operator= (const ring_iterator& it) noexcept {
+            base_ = it.base_;
+            iter_ = it.iter_;
+            return *this;
+        }
+    //! @}
+
+    //! \name Forward iterator requirements
+    //! @{
+    public:
+        constexpr reference operator*() const noexcept {
+            return *iter_;
+        }
+
+        constexpr pointer operator->() const noexcept {
+            return iter_;
+        }
+
+        constexpr ring_iterator& operator++() noexcept {
+            if (static_cast<size_t>(++iter_ - base_) >= N)
+                iter_ = base_;
+            return *this;
+        }
+
+        constexpr ring_iterator operator++(int) noexcept {
+            ring_iterator it = *this;
+            if (static_cast<size_t>(++iter_ - base_) >= N)
+                iter_ = base_;
+            return it;
+        }
+    //! @}
+
+    //! \name Bidirectional iterator requirements
+    //! @{
+    public:
+        constexpr ring_iterator& operator--() noexcept {
+            if (--iter_ < base_)
+                iter_ = base_ + N -1;
+            return *this;
+        }
+        constexpr ring_iterator operator--(int) noexcept {
+            ring_iterator it = *this;
+            if (--iter_ < base_)
+                iter_ = base_ + N -1;
+            return it;
+        }
+    //! @}
+
+    //! \name Random access iterator requirements
+    //! @{
+        constexpr reference operator[](difference_type n) const noexcept {
+            difference_type k = iter_ - base_;          // ptrdiff from base_
+            return (static_cast<size_t>(k + n) < N) ?
+                base_[k + n] :      // on range
+                base_[k + n - N];   // out of range, loop
+        }
+        constexpr ring_iterator& operator+=(difference_type n) noexcept {
+            difference_type k = iter_ - base_;          // ptrdiff from base_
+            iter_ += (static_cast<size_t>(k + n) < N) ?
+                n :                 // on range
+                n - N;              // out of range, loop
+            return *this;
+        }
+
+        constexpr ring_iterator operator+(difference_type n) const noexcept {
+            difference_type k = iter_ - base_;          // ptrdiff from base_
+            return (static_cast<size_t>(k + n) < N) ?
+                ring_iterator(base_, k + n) :           // on range
+                ring_iterator(base_, k + n - N);        // out of range, loop
+        }
+        constexpr ring_iterator& operator-=(difference_type n) noexcept {
+            difference_type k = iter_ - base_;          // ptrdiff from base_
+            iter_ -= ((k - n) < 0)?
+                n - N:                                  // out of range, loop
+                n;                                      // on range
+            return *this;
+        }
+        constexpr ring_iterator operator-(difference_type n) const noexcept {
+            difference_type k = iter_ - base_;          // ptrdiff from base_
+            return ((k - n) < 0) ?
+                ring_iterator(base_, k - n + N) :       // out of range, loop
+                ring_iterator(base_, k - n);            // on range
+        }
+    //! @}
+
+    //! \name Data members and access
+    //! @{
+        constexpr const Iter_t& base() const noexcept {
+            return base_;
+        }
+        constexpr const Iter_t& iter() const noexcept {
+            return iter_;
+        }
+        constexpr size_t size() noexcept {
+            return N;
+        }
+
+        constexpr operator Iter_t() noexcept { return iter_; }
+        constexpr operator const Iter_t() const noexcept { return iter_; }
+
+    protected:
+        Iter_t base_;
+        Iter_t iter_;
+    //! @}
+};
+
+// Forward iterator requirements
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator==(const ring_iterator<Iter_L, N>& lhs, const ring_iterator<Iter_R, N>& rhs)
+noexcept {
+    return lhs.iter() == rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator!=(const ring_iterator<Iter_L, N>& lhs, const ring_iterator<Iter_R, N>& rhs)
+noexcept {
+    return lhs.iter() != rhs.iter();
+}
+
+// Random access iterator requirements
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator<(const ring_iterator<Iter_L, N>& lhs, const ring_iterator<Iter_R, N>& rhs)
+noexcept {
+    return lhs.iter() < rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator<=(const ring_iterator<Iter_L, N>& lhs, const ring_iterator<Iter_R, N>& rhs)
+noexcept {
+    return lhs.iter() <= rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator>(const ring_iterator<Iter_L, N>& lhs, const ring_iterator<Iter_R, N>& rhs)
+noexcept {
+    return lhs.iter() > rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator>=(const ring_iterator<Iter_L, N>& lhs, const ring_iterator<Iter_R, N>& rhs)
+noexcept {
+    return lhs.iter() >= rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline auto operator-(const ring_iterator<Iter_L, N>& lhs, const ring_iterator<Iter_R, N>& rhs)
+noexcept
+-> decltype(lhs.iter() - rhs.iter()) {
+    auto diff = lhs.iter() - rhs.iter();
+    return diff < 0 ?
+            diff + N :  // loop
+            diff;       // no loop
+}
+
+template<typename Iter, size_t N>
+inline ring_iterator<Iter, N> operator+(std::ptrdiff_t lhs, const ring_iterator<Iter, N>& rhs)
+noexcept {
+    ring_iterator<Iter, N> it(rhs.iter());
+    return it += lhs;
+}
+
+
+
+
+
+
+template<typename Iter_t, size_t N>
+class ring_iterator<Iter_t, N, true> {
+    //! \name STL iterator traits "forwarding"
+    //! @{
+    protected:
+        using traits_type = std::iterator_traits<Iter_t>;
+
+    public:
+        using iterator_type     = Iter_t;
+        using iterator_category = typename traits_type::iterator_category;
+        using value_type        = typename traits_type::value_type;
+        using difference_type   = typename traits_type::difference_type;
+        using reference         = typename traits_type::reference;
+        using pointer           = typename traits_type::pointer;
+    //! @}
+
+
+    //! \name Constructor / Destructor
+    //! @{
+    public:
+        constexpr ring_iterator(const Iter_t base =nullptr) noexcept :
+            base_(base), iter_(base) { }
+
+        constexpr ring_iterator(const Iter_t base, size_t elem) noexcept :
+            base_(base), iter_(base + elem) { }
+
+        constexpr ring_iterator(const ring_iterator& it) noexcept :
+            base_(it.base_) {
+            iter_ =  it.iter_.load(std::memory_order_acquire);
+        }
+
+        constexpr ring_iterator& operator= (const ring_iterator& it) noexcept {
+            base_ = it.base_;
+            iter_ = it.iter_.load(std::memory_order_acquire);
+            return *this;
+        }
+    //! @}
+
+    //! \name Forward iterator requirements
+    //! @{
+    public:
+        constexpr reference operator*() const noexcept {
+            return *iter_.load(std::memory_order_acquire);
+        }
+
+        constexpr pointer operator->() const noexcept {
+            return iter_.load(std::memory_order_acquire);
+        }
+
+        constexpr ring_iterator& operator++() noexcept {
+            Iter_t itnew, it = iter_.load(std::memory_order_acquire);
+            do {
+                itnew = it;
+                if (static_cast<size_t>(++itnew - base_) >= N)
+                    itnew = base_;
+            } while (!iter_.compare_exchange_weak(it, itnew, std::memory_order_acq_rel));
+            return *this;
+        }
+        constexpr ring_iterator operator++(int) noexcept {
+            ring_iterator ret = *this;
+            Iter_t itnew, it = iter_.load(std::memory_order_acquire);
+            do {
+                itnew = it;
+                if (static_cast<size_t>(++itnew - base_) >= N)
+                    itnew = base_;
+            } while (!iter_.compare_exchange_weak(it, itnew, std::memory_order_acq_rel));
+            return ret;
+        }
+    //! @}
+
+    //! \name Bidirectional iterator requirements
+    //! @{
+    public:
+        constexpr ring_iterator& operator--() noexcept {
+            Iter_t itnew, it = iter_.load(std::memory_order_acquire);
+            do {
+                itnew = it;
+                if (--itnew < base_)
+                    itnew = base_ + N -1;
+            } while (!iter_.compare_exchange_weak(it, itnew, std::memory_order_acq_rel));
+            return *this;
+        }
+        constexpr ring_iterator operator--(int) noexcept {
+            ring_iterator ret = *this;
+            Iter_t itnew, it = iter_.load(std::memory_order_acquire);
+            do {
+                itnew = it;
+                if (--itnew < base_)
+                    itnew = base_ + N -1;
+            } while (!iter_.compare_exchange_weak(it, itnew, std::memory_order_acq_rel));
+            return ret;
+        }
+    //! @}
+
+    //! \name Random access iterator requirements
+    //! @{
+        constexpr reference operator[](difference_type n) const noexcept {
+            difference_type k = iter_.load(std::memory_order_acquire) - base_; // ptrdiff from base_
+            return (static_cast<size_t>(k + n) < N) ?
+                base_[k + n] :                          // on range
+                base_[k + n - N];                       // out of range, loop
+        }
+        constexpr ring_iterator& operator+=(difference_type n) noexcept {
+            Iter_t itnew, it = iter_.load(std::memory_order_acquire);
+            do {
+                itnew = it;
+                difference_type k = it - base_;         // ptrdiff from base_
+                itnew += (static_cast<size_t>(k + n) < N) ?
+                    n :                                 // on range
+                    n - N;                              // out of range, loop
+            } while (!iter_.compare_exchange_weak(it, itnew, std::memory_order_acquire));
+            return *this;
+        }
+        constexpr ring_iterator operator+(difference_type n) const noexcept {
+            difference_type k = iter_.load(std::memory_order_acquire) - base_; // ptrdiff from base_
+            return (static_cast<size_t>(k + n) < N) ?
+                ring_iterator(base_, k + n) :           // on range
+                ring_iterator(base_, k + n - N);        // out of range, loop
+        }
+        constexpr ring_iterator& operator-=(difference_type n) noexcept {
+            Iter_t itnew, it = iter_.load(std::memory_order_acquire);
+            do {
+                itnew = it;
+                difference_type k = it - base_;         // ptrdiff from base_
+                itnew -= ((k - n) < 0)?
+                    n - N:                              // out of range, loop
+                    n;                                  // on range
+            } while (!iter_.compare_exchange_weak(it, itnew, std::memory_order_acquire));
+            return *this;
+        }
+        constexpr ring_iterator operator-(difference_type n) const noexcept {
+            difference_type k = iter_.load(std::memory_order_acquire) - base_; // ptrdiff from base_
+            return ((k - n) < 0) ?
+                ring_iterator(base_, k - n + N) :       // out of range, loop
+                ring_iterator(base_, k - n);            // on range
+        }
+    //! @}
+
+    //! \name Data members and access
+    //! @{
+        constexpr const Iter_t& base() const noexcept {
+            return base_;
+        }
+        constexpr const Iter_t iter() const noexcept {
+            return iter_.load(std::memory_order_acquire);
+        }
+        constexpr size_t size() noexcept {
+            return N;
+        }
+
+        constexpr operator Iter_t() noexcept { return iter_.load(std::memory_order_acquire); }
+        constexpr operator const Iter_t() const noexcept { return iter_.load(std::memory_order_acquire); }
+
+    protected:
+        Iter_t base_;
+        std::atomic<Iter_t> iter_;
+    //! @}
+};
+
+// Forward iterator requirements
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator==(const ring_iterator<Iter_L, N, true>& lhs, const ring_iterator<Iter_R, N, true>& rhs)
+noexcept {
+    return lhs.iter() == rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator!=(const ring_iterator<Iter_L, N, true>& lhs, const ring_iterator<Iter_R, N, true>& rhs)
+noexcept {
+    return lhs.iter() != rhs.iter();
+}
+
+// Random access iterator requirements
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator<(const ring_iterator<Iter_L, N, true>& lhs, const ring_iterator<Iter_R, N, true>& rhs)
+noexcept {
+    return lhs.iter() < rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator<=(const ring_iterator<Iter_L, N, true>& lhs, const ring_iterator<Iter_R, N, true>& rhs)
+noexcept {
+    return lhs.iter() <= rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator>(const ring_iterator<Iter_L, N, true>& lhs, const ring_iterator<Iter_R, N, true>& rhs)
+noexcept {
+    return lhs.iter() > rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline bool operator>=(const ring_iterator<Iter_L, N, true>& lhs, const ring_iterator<Iter_R, N, true>& rhs)
+noexcept {
+    return lhs.iter() >= rhs.iter();
+}
+
+template<typename Iter_L, typename Iter_R, size_t N>
+inline auto operator-(const ring_iterator<Iter_L, N, true>& lhs, const ring_iterator<Iter_R, N, true>& rhs)
+noexcept
+-> decltype(lhs.iter() - rhs.iter()) {
+    auto diff = lhs.iter() - rhs.iter();
+    return diff < 0 ?
+            diff + N :  // loop
+            diff;       // no loop
+}
+
+template<typename Iter, size_t N>
+inline ring_iterator<Iter, N, true> operator+(std::ptrdiff_t lhs, const ring_iterator<Iter, N, true>& rhs)
+noexcept {
+    ring_iterator<Iter, N, true> it(rhs.iter());
+    return it += lhs;
+}
+
+} //namespace utl;
+
+#endif /* utl_container_ring_iterator_h__ */

include/utl/dev/cli_device.h

@@ -0,0 +1,473 @@
+/*!
+ * \file dev/cli_device.h
+ * \brief
+ *      command line device driver functionality as CRTP base class
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_dev_cli_device_h__
+#define utl_dev_cli_device_h__
+
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
+#include <utl/container/equeue.h>
+#include <utl/dev/sequencer.h>
+
+#include <utl/meta/meta.h>
+
+#include <cstring>
+#include <cstdlib>
+#include <algorithm>
+
+#include <utility>
+#include <atomic>
+
+namespace utl {
+
+/*!
+ * \class cli_device
+ * \brief
+ *      Its a base class for command-line based devices
+ *
+ * Inherits the sequencer functionality and provides a command interface for sending
+ * commands and parse the response.
+ *
+ * \example implementation example
+ * \code
+ * class BG95 : public cli_device<BG95, 256> {
+ *     using base_type = cli_device<BG95, 256>;
+ *     using Queue     = equeue<typename base_type::value_type, 256, true>;
+ *         Queue RxQ{};
+ *         std::atomic<size_t> lines{};
+ *     public:
+ *         // cli_device driver requirements
+ *         BG95() noexcept :
+ *             RxQ(Queue::data_match::MATCH_PUSH, base_type::delimiter, [&](){
+ *                 lines.fetch_add(1, std::memory_order_acq_rel);
+ *             }), lines(0) { }
+ *         void feed(char x) { RxQ << x; } // To be used inside ISR
+ *         size_t get(char* data, bool wait =false) {
+ *             do {
+ *                 if (lines.load(std::memory_order_acquire)) {
+ *                     size_t n =0;
+ *                     do{
+ *                         *data << RxQ;
+ *                         ++n;
+ *                     } while (*data++ != base_type::delimiter);
+ *                     lines.fetch_sub(1, std::memory_order_acq_rel);
+ *                     return n;
+ *                 }
+ *             } while (wait);
+ *             return 0;
+ *         }
+ *         size_t contents(char* data) {
+ *             char* nullpos = std::copy(RxQ.begin(), RxQ.end(), data);
+ *             *nullpos =0;
+ *             return nullpos - data;
+ *         }
+ *         size_t put (const char* data, size_t n) {
+ *             // send data to BG95
+ *             return n;
+ *         }
+ *         clock_t clock() noexcept { //return CPU time }
+ * };
+ * \endcode
+ *
+ * \tparam Impl_t       The type of derived class
+ * \tparam N            The size of the queue buffer for the receive/command interface
+ * \tparam Delimiter    The incoming data delimiter [default line buffered -- Delimiter = '\n']
+ */
+template<typename Impl_t, size_t N, char Delimiter ='\n'>
+class cli_device
+        : public sequencer<cli_device<Impl_t, N, Delimiter>, char, N>{
+        _CRTP_IMPL(Impl_t);
+
+        // local type dispatch
+        using base_type     = sequencer<cli_device, char, N>;
+
+    //! \name Public types
+    //! @{
+    public:
+        using value_type    = char;
+        using pointer_type  = char*;
+        using size_type     = size_t;
+        using string_view   = typename base_type::string_view;
+
+        using action_t      = typename base_type::action_t;
+        using control_t     = typename base_type::control_t;
+        using match_ft      = typename base_type::match_ft;
+        using handler_ft    = typename base_type::handler_ft;
+        template<size_t Nm>
+        using script_t      = typename base_type::template script_t<Nm>;
+
+        //! Publish delimiter
+        constexpr static char delimiter = Delimiter;
+
+        enum flush_type { keep =0, flush };
+
+        //! Required types for inetd async handler operation
+        //! @{
+
+        /*!
+         * inetd handler structure for asynchronous incoming data dispatching
+         */
+        struct inetd_handler_t {
+            string_view token;      //!< The token we match against
+            match_ft    match;      //!< The predicate we use to match
+            handler_ft  handler;    //!< The handler to call on match
+        };
+        //! Alias template for the async handler array
+        template <size_t Nm>
+        using inetd_handlers    = std::array<inetd_handler_t, Nm>;
+        //! @}
+    //! @}
+
+    //! \name object lifetime
+    //!@{
+    protected:
+        //!< \brief A default constructor from derived only
+        cli_device() noexcept = default;
+        ~cli_device () = default;                           //!< \brief Allow destructor from derived only
+        cli_device(const cli_device&) = delete;             //!< No copies
+        cli_device& operator= (const cli_device&) = delete; //!< No copy assignments
+    //!@}
+
+    //! \name Sequencer interface requirements
+    //!     Forwarded to implementer the calls and cascade the the incoming channel
+    //! @{
+    friend base_type;
+
+    private:
+        size_t get_ (char* data) {
+            return impl().get (data);
+        }
+        size_t get (char* data) {
+            return receive (data);
+        }
+        size_t contents (char* data) {
+            return impl().contents(data);
+        }
+        size_t put (const char* data, size_t n) {
+            return impl().put (data, n);
+        }
+        clock_t clock () noexcept {
+            return impl().clock();
+        }
+    //! @}
+
+    //! \name Private functionality
+    //! @{
+    private:
+
+        /*!
+         * Convert the text pointed by \c str to a value and store it to
+         * \c value. The type of conversion is deduced by the compiler
+         * \tparam  T       The type of the value
+         * \param str       pointer to string with the value
+         * \param value     pointer to converted value
+         */
+        template<typename T>
+        void extract_ (const char* str, T* value) {
+            static_assert (
+                    std::is_same_v<std::remove_cv_t<T>, int>
+                ||  std::is_same_v<std::remove_cv_t<T>, double>
+                ||  std::is_same_v<std::remove_cv_t<T>, char>,
+                "Not supported conversion type.");
+            if constexpr (std::is_same_v<std::remove_cv_t<T>, int>) {
+                *value = std::atoi(str);
+            } else if (std::is_same_v<std::remove_cv_t<T>, double>) {
+                *value = std::atof(str);
+            } else if (std::is_same_v<std::remove_cv_t<T>, char>) {
+                std::strcpy(value, str);
+            }
+        }
+        //! Specialization (as overload function) to handle void* types
+        void extract_ (const char* str, void* value) noexcept {
+            (void)*str; (void)value;
+        }
+
+        /*!
+         * Parse a chunk of the buffer based on \c expected character
+         *
+         * Tries to match the \c *expected character in buffer and if so it copies the
+         * character to token.
+         * If the \c *expected is the \c Marker character, copy the entire chunk of the buffer
+         * up to the character that matches the next expected character (expected[1]).
+         * If there is no next expected character or if its not found in the buffer,
+         * copy the entire buffer.
+         *
+         * \tparam  Marker  The special character to indicate chunk extraction
+         *
+         * \param expected  The character to parse/remove from the buffer
+         * \param buffer    The buffer we parse
+         * \param token     Pointer to store the parsed tokens
+         * \return          A (number of characters parsed, marker found) pair
+         */
+        template <char Marker = '%'>
+        std::pair<size_t, bool> parse_ (const char* expected, const string_view buffer, char* token) {
+            do {
+                if (*expected == Marker) {
+                    // We have Marker. Copy the entire chunk of the buffer
+                    // up to the character that matches the next expected character (expected[1]).
+                    // If there is none next expected character or if its not found in the buffer,
+                    // copy the entire buffer.
+                    auto next = std::find(buffer.begin(), buffer.end(), expected[1]);
+                    char* nullpos = std::copy(buffer.begin(), next, token);
+                    *nullpos =0;
+                    return std::make_pair(next - buffer.begin(), true);
+                }
+                else if (*expected == buffer.front()) {
+                    // We have character match, copy the character to token and return 1 (the char size)
+                    *token++ = buffer.front();
+                    *token =0;
+                    return std::make_pair(1, false);
+                }
+            } while (0);
+
+            // Fail to parse
+            *token =0;
+            return std::make_pair(0, false);
+        }
+
+
+        /*!
+         * Analyze the response of a command based on \c expected.
+         *
+         * Tries to receive data with timeout and match them against expected string_view.
+         * For each Marker inside the expected string the value gets extracted, converted and
+         * copied to \c vargs pointer array.
+         *
+         * \param expected      The expected string view
+         * \param timeout       the timeout in CPU time
+         * \param vargs         Pointer to variable arguments array
+         * \param nargs         Size of variable arguments array
+         * \return
+         */
+        template<char Marker = '%', typename T>
+        bool response_ (const string_view expected, clock_t timeout, T* vargs, size_t nargs) {
+            char buffer[N], token[N], *pbuffer = buffer;
+
+            size_t v =0, sz =0;
+            for (auto ex = expected.begin() ; ex != expected.end() ;  ) {
+                clock_t mark = clock();                     // mark the time
+                while (sz <= 0) {                           // if buffer is empty get buffer with timeout
+                    sz = receive(buffer);
+                    pbuffer = buffer;
+                    if ((timeout != 0 )&& ((clock() - mark) >= timeout))
+                        return false;
+                }
+                // try to parse
+                auto [step, marker] = parse_<Marker> (ex, {pbuffer, sz}, token);
+                if (!step)
+                    return false;                           // discard buffer and fail
+
+                if (marker && v < nargs)
+                    extract_(token, vargs[v++]);
+
+                pbuffer += step;
+                sz      -= (step <= sz) ? step: sz;
+                ++ex;
+            }
+            return true;
+        }
+    //! @}
+
+    //! \name public functionality
+    //! @{
+    public:
+
+        /*!
+         * \brief
+         *   Transmit data to modem
+         * \param data   Pointer to data to send
+         * \param n      The size of data buffer
+         * \return       The number of transmitted chars
+         */
+        size_t transmit (const char* data, size_t n) {
+            if (data == nullptr)
+                return 0;
+            return put (data, n);
+        }
+
+        /*!
+         * \brief
+         *   Transmit data to modem
+         * \param data   Pointer to data to send
+         * \return       The number of transmitted chars
+         */
+        size_t transmit (const char* data) {
+            if (data == nullptr)
+                return 0;
+            return put (data, std::strlen(data));
+        }
+
+        /*!
+         * \brief
+         *   Try to receive data from modem. If there are data copy them to \c data pointer and return
+         *   the size. Otherwise return zero. In the case \c wait is true block until there are data to get.
+         *
+         * \param data   Pointer to data buffer to write
+         * \param wait   Flag to select blocking / non-blocking functionality
+         * \return       The number of copied data.
+         */
+        size_t receive (char* data, bool wait =false) {
+            do {
+                if (streams_.load(std::memory_order_acquire)) {
+                    size_t n =0;
+                    do {
+                        *data << rx_q;
+                        ++n;
+                    } while (*data++ != delimiter);
+                    *data =0;
+                    streams_.fetch_sub(1, std::memory_order_acq_rel);
+                    return n;
+                }
+            } while (wait);  // on wait flag we block until available stream
+            return 0;
+        }
+
+        //! Clears the incoming data buffer
+        void clear () noexcept {
+            rx_q.clear();
+        }
+
+        //! \return     Returns the size of the incoming data buffer
+        size_t size() noexcept {
+            return rx_q.size();
+        }
+
+        /*!
+         * \brief
+         *      Send a command to modem and check if the response matches to \c expected.
+         *
+         * This function executes 3 steps.
+         *  - Clears the incoming buffer if requested by template parameter
+         *  - Sends the command to device
+         *  - Waits to get the response and parse it accordingly to \c expected \see response_()
+         *
+         * The user can mark spots inside the expected string using the \c Marker ['%'] character.
+         * These spots will be extracted to tokens upon parsing. If the user passes \c values parameters,
+         * then the extracted tokens will be converted to the type of the \c values (\c Ts) and copied to them
+         * one by one. If the values are less than spots, the rest of the tokens get discarded.
+         *
+         * \param cmd       The command to send (null terminated)
+         * \param expected  The expected response
+         * \param timeout   The timeout in CPU time (leave it for 0 - no timeout)
+         * \param values    The value pointer arguments to get the converted tokens
+         *
+         * \tparam Flush    Flag to indicate if we flush the buffer before command or not
+         * \tparam Marker   The marker character
+         * \tparam Ts       The type of the values to read from response marked with \c Marker
+         * \warning         The types MUST be the same
+         *
+         * \return          True on success
+         *
+         * \example examples
+         * \code
+         *    Derived cli;
+         *    int status;
+         *    char str[32];
+         *
+         *    // discard 3 lines and expect OK\r\n at the end with 1000[CPU time] timeout
+         *    cli.command("AT+CREG?\r\n", "%%%OK\r\n", 1000);
+         *
+         *    // extract a number from response without timeout (blocking)
+         *    cli.command<flush>("AT+CREG?\r\n", "\r\n+CREG: 0,%\r\n\r\nOK\r\n", 0, &status);
+         *
+         *    // extract a number and discard the last 2 lines
+         *    cli.command<flush>("AT+CREG?\r\n", "\r\n+CREG: 0,%\r\n%%", 1000, &status);
+         *
+         *    // discard first line, read the 2nd to str, discard the 3rd line.
+         *    // expect the last to be "OK\r\n"
+         *    cli.command<flush>("AT+CREG?\r\n", "", 100000);
+         *    cli.command<keep>("", "%",  1000);
+         *    cli.command<keep>("", "%%", 1000, str);
+         *    cli.command<keep>("", "OK\r\n",  1000);
+         * \endcode
+         */
+        template<flush_type Flush =flush, char Marker = '%', typename ...Ts>
+        bool command (const string_view cmd, const string_view expected, clock_t timeout, Ts* ...values) {
+            constexpr size_t Nr = sizeof...(Ts);
+
+            meta::if_c<
+                (sizeof...(Ts) != 0),
+                meta::front<meta::typelist<Ts...>>*,
+                void*
+            > vargs[Nr] = {values...};        // read all args to local buffer
+            if constexpr (Flush == flush) {
+                clear ();
+            }
+            if (transmit(cmd.data(), cmd.size()) != cmd.size())     // send command
+                return false;
+            // parse the response and return the status
+            return response_<Marker>(expected, timeout, vargs, Nr);
+        }
+
+        /*!
+         * \brief
+         *   inetd daemon functionality provided as member function of the driver. This should be running
+         *   in the background either as consecutive calls from an periodic ISR with \c loop = false, or
+         *   as a thread in an RTOS environment with \c loop = true.
+         *
+         * \tparam Nm            The number of handler array entries
+         *
+         * \param async_handles  Reference to asynchronous handler array
+         * \param loop           Flag to indicate blocking mode. If true blocking.
+         */
+        template <size_t Nm =0>
+        void inetd (bool loop =true, const inetd_handlers<Nm>* inetd_handlers =nullptr) {
+            std::array<char, N> buffer;
+            size_t resp_size;
+            do {
+                if ((resp_size = get_(buffer.data())) != 0) {
+                    // on data check for async handlers
+                    bool match = false;
+                    if (inetd_handlers != nullptr) {
+                        for (auto& h : *inetd_handlers)
+                            match |= base_type::check_handle({buffer.data(), resp_size}, h.token, h.match, h.handler);
+                    }
+                    // if no match forward data to receive channel.
+                    if (!match) {
+                        char* it = buffer.data();
+                        do {
+                            rx_q << *it;
+                        } while (*it++ != delimiter);
+                        streams_.fetch_add(1, std::memory_order_acq_rel);
+                    }
+                }
+            } while (loop);
+        }
+
+    //! @}
+
+    private:
+        equeue<char, N, true> rx_q{};
+        std::atomic<size_t>   streams_{};
+};
+
+} // namespace utl;
+
+#endif /* #ifndef utl_dev_cli_device_h__ */

include/utl/dev/gpio_dev.h

@@ -0,0 +1,107 @@
+/*!
+ * \file dev/gpio_dev.h
+ * \brief
+ *      A STM32 gpio wrapper class
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_dev_gpio_dev_h__
+#define utl_dev_gpio_dev_h__
+
+#include <utl/core/impl.h>
+
+namespace utl {
+
+    /*!
+     * CRTP class for gpio digital input-output.
+     *
+     * The derived class requirements are:
+     *  - bool read_impl ()
+     *  - void write_impl(bool)
+     *
+     * \tparam  Impl_t  The type of derived class
+     */
+    template <typename Impl_t>
+    class DigitalInOut {
+    public:
+            _CRTP_IMPL(Impl_t);
+
+        /*!
+         * \name Object lifetime
+         */
+        //! @{
+        protected:
+            DigitalInOut() noexcept = default;
+            ~DigitalInOut() = default;
+            DigitalInOut(const DigitalInOut&)             = delete;   //!< No copy constructions
+            DigitalInOut operator=(const DigitalInOut&)   = delete;   //!< No copies
+
+        //! @}
+
+        //! \name Public interface
+        //! @{
+        public:
+            //! Reads the state of the pin. This is true for both input and output pins.
+            //! \return     The state of the pin
+            bool read () noexcept { return impl().read_impl (); }
+            //! Write a new state to pin. If the pin is set for output, otherwise this state will remain
+            //! to pin registers and reflect to the pin state if we select output mode
+            void write (bool state) noexcept { impl().write_impl(state); }
+
+            //! Implicit conversion to bool for reading operations
+            operator bool () noexcept {
+                return read();
+            }
+            //! Stream from bool for write operations
+            DigitalInOut& operator<< (bool state) noexcept {
+                write(state);
+                return *this;
+            }
+            //! Right stream to bool for read operations
+            DigitalInOut& operator>> (bool& state) noexcept {
+                state = read();
+                return *this;
+            }
+        //! @}
+    };
+
+    /*!
+     * This definition enables the "data << pin" syntax for read operation
+     *
+     * \tparam Impl_t   The derived class type of the DigitalInOut
+     *
+     * \param lhs   Left hand site operand
+     * \param rhs   Right hand site operand
+     * \return      The read value
+     */
+    template<typename Impl_t>
+    bool operator<<(bool& lhs, DigitalInOut<Impl_t>& rhs) noexcept {
+        lhs = rhs.read();
+        return lhs;
+    }
+}
+
+#endif //#ifndef utl_dev_gpio_dev_h__

include/utl/dev/sequencer.h

@@ -0,0 +1,492 @@
+/*!
+ * \file dev/sequencer.h
+ * \brief
+ *      A script based automation tool for send/receive communications
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_dev_dequencer_h__
+#define utl_dev_dequencer_h__
+
+#include <utl/core/impl.h>
+#include <utl/container/range.h>
+
+#include <ctime>
+#include <array>
+#include <string_view>
+#include <type_traits>
+#include <utility>
+#include <tuple>
+
+namespace utl {
+
+/*!
+ * \class sequencer
+ * \brief
+ *      A CRTP base class to provide the sequencer functionality.
+ *
+ * Sequencer is a script engine with receive/transmit functionalities based on predicates. It has:
+ *  - A program counter like variable named \c step.
+ *  - \c step actions like NEXT, GOTO exit with status etc...
+ *  - Input data match predicates to trigger those actions.
+ *  - Input data handlers to trigger external functionality on predicate match
+ *  - Output data handlers to "edit" data before transmiting them
+ *  - A small predicate set provided to the user. (starts_with, ends_with, contains).
+ *
+ * Sequencer can automate communication with a terminal-like device such as AT-command modems, can
+ * be used to implement communication protocols, or even small http servers.
+ *
+ * It can operate based on a script array and handle the outgoing commands and incoming responses.
+ * The user can create matching rules on received data and hook handlers and actions on them.
+ *
+ * The derived class (implementation) has to provide:
+ *  1) size_t get(Data_t* data);
+ *     This function return 0 or a number of Data_t items. The data points to buffer for the input data.
+ *
+ *  3) size_t contents_ (Data_t* data);
+ *     This function return 0 or a number of Data_t items without removing them from the implementer's container
+ *     The data points to buffer for the input data.
+ *
+ *  2) size_t put(const Data_t* data, size_t n);
+ *     This function sends to implementation the data pointed by \c data witch have size \c n.
+ *
+ *  4) clock_t clock();
+ *     This function return a number to be used as time. The units of this function may be arbitrary but they
+ *     match the units in \c record_t::timeout field.
+ *
+ * \tparam Impl_t   The type of derived class
+ * \tparam Data_t   The char-like stream item type. Usually \c char
+ * \tparam N        The size of the sequence buffer to temporary store each line from get().
+ *
+ * \note
+ *      We need access to derived class container to sneaky get a range of the data beside
+ *      the normal data flow, in order to implement the \see control_t::DETECT operation.
+ */
+template <typename Impl_t, typename Data_t, size_t N>
+class sequencer {
+    _CRTP_IMPL(Impl_t);
+
+    //! \name Public types
+    //! @{
+    public:
+        using value_type    = Data_t;
+        using pointer_type  = Data_t*;
+        using size_type     = size_t;
+        using string_view   = std::basic_string_view<Data_t>;
+
+        /*!
+         * The sequencer engine status. A variable of this type is returned by
+         * \see action_().
+         */
+        enum class seq_status_t {
+            CONTINUE,   //!< Means we keep looping
+            EXIT        //!< Means, we exit with status the one indicated by \c action_t of the \c record_t
+        };
+
+        //! \enum control_t
+        //! \brief The control type of the script entry.
+        enum class control_t {
+            NOP,        //!< No command, dont send or expect anything, used for delays
+            SEND,       //!< Send data to implementation through put()
+            EXPECT,     //!< Expects data from implementation via get()
+            OR_EXPECT,  //!< Expects data from implementation via get() in conjunction with previous EXPECT
+            DETECT,     //!< Detects data into rx buffer without receiving them via contents()
+            OR_DETECT   //!< Detects data into rx buffer without receiving them via contents() in conjunction with
+                        //!< previous DETECT
+
+            //! \note
+            //! The \c DETECT extra incoming channel serve the purpose of sneak into receive
+            //! buffer and check for data without getting them. This is useful when the receive driver
+            //! is buffered with a delimiter and we seek for data that don't follow the delimiter pattern.
+            //!
+            //! For example:
+            //! A modem sends responses with '\n' termination but for some "special" command it opens a cursor
+            //! lets say ">$ " without '\n' at the end.
+        };
+
+        //! \enum action_t
+        //! \brief
+        //!     Possible response actions for the sequencer. This is the
+        //!     equivalent of changing the program counter of the sequencer
+        //!     and is composed by a type and a value.
+        //!
+        struct action_t {
+            enum {
+                NO =0,      //!< Do not change sequencer's step
+                NEXT,       //!< Go to next sequencer step. In case of EXPECT/DETECT block of records
+                            //!< skip the entire block of EXPECT[, OR_EXPECT[, OR_EXPECT ...]] and go
+                            //!< to the next (non OR_*) control record.
+                GOTO,       //!< Manually sets the step counter to the number of the \c step member.
+                EXIT,       //!< Instruct for an exit returning the action.value as status
+            } type;
+            size_t value;   //!< Used by \c GOTO to indicate the next sequencer's step.
+        };
+
+        //! A no_action action_t
+        static constexpr action_t no_action  = {action_t::NO, 0};
+        //! A next action_t
+        static constexpr action_t next       = {action_t::NEXT, 0};
+        //! A goto action_t template
+        template <size_t GOTO>
+        static constexpr action_t go_to      = {action_t::GOTO, static_cast<size_t>(GOTO)};
+
+        //! An exit ok action_t
+        static constexpr action_t exit_ok    = {action_t::EXIT, 0};
+        //! An exit error action_t
+        static constexpr action_t exit_error = {action_t::EXIT, static_cast<size_t>(-1)};
+        //! A generic exit action_t template
+        template <size_t Status>
+        static constexpr action_t exit       = {action_t::EXIT, static_cast<size_t>(Status)};
+
+        /*!
+         * Match binary predicate function pointer type.
+         * Expects two string views and return a boolean.
+         * It is used by EXPECT/DETECT blocks to trigger their {handler, action} pair.
+         */
+        using match_ft   = bool (*) (const string_view haystack, const string_view needle);
+
+        /*!
+         *  Send/Receive handler function pointer type.
+         *  Expects a pointer to buffer and a size and returns status.
+         *  It is used on predicate match on EXPECT/DETECT blocks, or as data wrapper on SEND blocks.
+         */
+        using handler_ft = void (*) (const Data_t*, size_t);
+
+        /*!
+         * \struct record_t
+         * \brief
+         *      Describes the sequencer's script record entry (line).
+         */
+        struct record_t {
+            control_t   control;    //!< The control type of the entry
+            string_view token;      //!< String view to token data. [MUST BE null terminated].
+                                    //!< This is passed as 2nd argument to match predicate on EXPECT/DETECT, or as
+                                    //! {data, size} pair to SEND handler and put_().
+                                    //!< If unused set it to ""
+            match_ft    match;      //!< Match predicate to used in EXPECT/DETECT blocks
+                                    //!< If unused set it to nullptr
+            handler_ft  handler;    //!< The handler to called if the match is successful, or before put_()
+                                    //!< If unused set it to nullptr
+            action_t    action;     //!< Indicates the step manipulation if the match is successful or after NOP and put_()
+            clock_t     timeout;    //!< Timeout in CPU time
+        };
+
+        /*!
+         * \struct script_t
+         * \brief
+         *      Describes the sequencer's script.
+         *
+         * The user can create arrays as the example bellow to act as a script.
+         * \code
+         * Seq s;
+         * const Seq::script_t<4> script = {{
+         *     {Seq::control_t::NOP,       "",         Seq::nil,       Seq::nil, {Seq::action_t::GOTO, 1},       1000},
+         *
+         *     {Seq::control_t::SEND,      "ATE0\r\n", Seq::nil,       Seq::nil, {Seq::action_t::NEXT, 0},       0},
+         *     {Seq::control_t::EXPECT,    "OK\r\n",   Seq::ends_with, Seq::nil, {Seq::action_t::EXIT_OK, 0},    1000},
+         *     {Seq::control_t::OR_EXPECT, "ERROR",    Seq::contains,  Seq::nil, {Seq::action_t::EXIT_ERROR, 0}, 0}
+         * }};
+         * s.run(script);
+         * \endcode
+         */
+        template <size_t Nrecords>
+        using script_t = std::array<record_t, Nrecords>;
+
+
+        /*!
+         * \brief
+         *       Check if the \c stream1 is equal to \c stream2
+         * \param stream1    The stream in witch we search [The input buffer]
+         * \param stream2    What we search [The record's token]
+         * \return           True on success, false otherwise
+         */
+        static constexpr auto equals = [](const string_view stream1, const string_view stream2) noexcept -> bool {
+            return (stream1 == stream2);
+        };
+
+        /*!
+         * \brief
+         *       Check if the \c stream starts with the \c prefix
+         * \param stream     The stream in witch we search [The input buffer]
+         * \param prefix     What we search [The record's token]
+         * \return           True on success, false otherwise
+         */
+        static constexpr auto starts_with = [](const string_view stream, const string_view prefix) noexcept -> bool {
+            return (stream.rfind(prefix, 0) != string_view::npos);
+        };
+
+        /*!
+         * \brief
+         *       Check if the \c stream ends with the \c postfix
+         * \param stream     The stream in witch we search [The input buffer]
+         * \param postfix    What we search [The record's token]
+         * \return           True on success, false otherwise
+         */
+        static constexpr auto ends_with = [](const string_view stream, const string_view postfix) -> bool {
+            if (stream.size() < postfix.size())
+                return false;
+            return (
+                stream.compare(
+                    stream.size() - postfix.size(),
+                    postfix.size(),
+                    postfix) == 0
+                );
+        };
+
+        /*!
+         * \brief
+         *       Check if the \c haystack contains the \c needle
+         * \param haystack   The stream in witch we search [The input buffer]
+         * \param needle     What we search [The record's token]
+         * \return           True on success, false otherwise
+         */
+        static constexpr auto contains = [](const string_view haystack, const string_view needle) noexcept -> bool {
+            return (haystack.find(needle) != string_view::npos);
+        };
+
+        //! Always false predicate
+        static constexpr auto always_true = [](const string_view s1, const string_view s2) noexcept -> bool {
+            (void)s1; (void)s2;
+            return true;
+        };
+
+        //! Always false predicate
+        static constexpr auto always_false = [](const string_view s1, const string_view s2) noexcept -> bool {
+            (void)s1; (void)s2;
+            return false;
+        };
+
+        //! Empty predicate or handler
+        static constexpr auto nil = nullptr;
+    //! @}
+
+
+
+    //! \name Object lifetime
+    //!@{
+    protected:
+       ~sequencer () = default;                             //!< \brief Allow destructor from derived only
+       constexpr sequencer () noexcept = default;           //!< \brief A default constructor from derived only
+       sequencer(const sequencer&) = delete;                //!< No copies
+       sequencer& operator= (const sequencer&) = delete;    //!< No copy assignments
+    //!@}
+
+    //! \name Sequencer interface requirements for implementer
+    //! @{
+    private:
+       size_t get_ (Data_t* data) { return impl().get (data); }
+       size_t contents_ (Data_t* data) { return impl().contents(data); }
+       size_t put_ (const Data_t* data, size_t n) { return impl().put (data, n); }
+       clock_t clock_ () noexcept { return impl().clock(); }
+    //! @}
+
+    //! \name Private functionality
+    //! @{
+    private:
+
+       /*!
+        * Check if there is a handler and call it
+        * \param handler    The handler to check
+        * \param buffer     String view to buffer to pass to handler
+        * \return           True if handler is called
+        */
+       constexpr bool handle_ (handler_ft handler, const string_view buffer = string_view{}) {
+           if (handler != nullptr) {
+               handler (buffer.begin(), buffer.size());
+               return true;
+           }
+           return false;
+       }
+
+       /*!
+        * \brief
+        *   Return the new sequencer's step value and the sequencer's loop status as pair.
+        *
+        * \param script         Reference to entire script.
+        * \param step           The current step
+        * \return               new step - status pair
+        */
+       template <size_t Steps>
+       constexpr std::pair<size_t, seq_status_t> action_ (const script_t<Steps>& script, size_t step) {
+           control_t skip_while{};
+           size_t s;
+
+           switch (script[step].action.type) {
+               default:
+               case action_t::NO:                   return std::make_pair(step, seq_status_t::CONTINUE);
+               case action_t::NEXT:
+                   switch (script[step].control) {
+                       case control_t::NOP:         return std::make_pair(++step, seq_status_t::CONTINUE);
+                       case control_t::SEND:        return std::make_pair(++step, seq_status_t::CONTINUE);
+                       case control_t::EXPECT:
+                       case control_t::OR_EXPECT:   skip_while = control_t::OR_EXPECT; break;
+                       case control_t::DETECT:
+                       case control_t::OR_DETECT:   skip_while = control_t::OR_DETECT; break;
+                   }
+                   s = step;
+                   while (script[++s].control == skip_while)
+                       ;
+                                                    return std::make_pair(s, seq_status_t::CONTINUE);
+               case action_t::GOTO:                 return std::make_pair(script[step].action.value, seq_status_t::CONTINUE);
+               case action_t::EXIT:                 return std::make_pair(script[step].action.value, seq_status_t::EXIT);
+
+           }
+       }
+
+    //! @}
+
+
+    public:
+
+       //! \return   The buffer size of the sequencer
+       constexpr size_t size() const noexcept { return N; }
+
+       /*!
+        * \brief
+        *       A static functionality to provide access to sequencer's inner matching mechanism.
+        *       Checks the \c buffer against \c handle and calls its action if needed.
+        *
+        * \param buffer     The buffer to check (1st parameter to match)
+        * \param token      String view to check against buffer (2nd parameter to match)
+        * \param handler    Function pointer to match predicate to use
+        * \param handle     Reference to handle to call on match
+        *
+        * \return           True on match, false otherwise
+        */
+       constexpr bool check_handle (const string_view buffer, const string_view token, match_ft match, handler_ft handle) {
+           if (match != nullptr && match(buffer, token))
+               return handle_ (handle, buffer);
+           return false;
+       }
+
+       /*!
+        * \brief
+        *   Run the script array
+        *
+        * The main sequencer functionality. It starts with the first entry of the array.
+        *
+        * - If the record is \c NOP it executes the action after the timeout.
+        *   \c NOP uses {\c action_t, \c timeout}.
+        * - If the record is \c SEND passes the token to handler (if any), then to put_() and executes the action after that.
+        *   \c SEND uses {\c token, \c handler, \c action_t}
+        * - If the record is \c EXCEPT it continuously try to receive data using \see get_()
+        *     * If no data until timeout, exit with failure
+        *     * On data reception for this record AND for each OR_EXPECT that follows, calls the match predicate
+        *       by passing the received data and token.
+        *       On predicate match
+        *         - Calls the handler if there is one
+        *         - Executes the action. No farther EXPECT, OR_EXPECT, ... checks are made.
+        * - If the record is \c DETECT it continuously try to receive data using \see contents_()
+        *     * If no data until timeout, exit with failure
+        *     * On data reception for this record AND for each OR_DETECT that follows, calls the match predicate
+        *       by passing the received data and token.
+        *       On predicate match
+        *         - Calls the handler if there is one
+        *         - Executes the action. No farther DETECT, OR_DETECT, ... checks are made.
+        *
+        * \tparam Steps     The number of records of the script
+        *
+        * \param script     Reference to script to run
+        * \return           The status of entire operation as described above
+        *   \arg            0       Success
+        *   \arg   (size_t)-1       Failure
+        *   \arg        other       Arbitrary return status
+        */
+       template <size_t Steps>
+       size_t run (const script_t<Steps>& script) {
+           Data_t buffer[N];
+           size_t resp_size;
+
+           size_t step =0, p_step =0;
+           clock_t mark = clock_();
+
+           seq_status_t status{seq_status_t::CONTINUE}; do {
+               if (step >= Steps)
+                   return exit_error.value;
+               const record_t& record = script[step];   // get reference ot current line
+
+               if (step != p_step) {                    // renew time marker in each step
+                   p_step = step;
+                   mark = clock_();
+               }
+               switch (record.control) {
+                   default:
+                   case control_t::NOP:
+                       if ((clock_() - mark) >= record.timeout)
+                           std::tie(step, status) = action_ (script, step);
+                       break;
+
+                   case control_t::SEND:
+                       if (record.handler != nullptr)
+                           record.handler(record.token.data(), record.token.size());
+                       if (put_(record.token.data(), record.token.size()) != record.token.size())
+                	       return exit_error.value;
+                	   std::tie(step, status) = action_ (script, step);
+                       break;
+
+                   case control_t::EXPECT:
+                   case control_t::OR_EXPECT:
+                       resp_size = get_(buffer);
+                       if (resp_size) {
+                           size_t s = step ; do{
+                               if (script[s].match != nullptr && script[s].match({buffer, resp_size}, script[s].token)) {
+                                   handle_ (script[s].handler, {buffer, resp_size});
+                                   std::tie(step, status) = action_ (script, s);
+                                   break;
+                               }
+                           } while ((++s < Steps) && (script[s].control == control_t::OR_EXPECT));
+                       }
+                       if (record.timeout && (clock_() - mark) >= record.timeout)
+                           return exit_error.value;
+                       break;
+
+                   case control_t::DETECT:
+                   case control_t::OR_DETECT:
+                       resp_size = contents_(buffer);
+                       if (resp_size) {
+                           size_t s = step ; do {
+                               if (script[s].match != nullptr && script[s].match({buffer, resp_size}, script[s].token)) {
+                                   handle_ (script[s].handler, {buffer, resp_size});
+                                   std::tie(step, status) = action_ (script, s);
+                                   break;
+                               }
+                           } while ((++s < Steps) && (script[s].control == control_t::OR_DETECT));
+                       }
+                       if (record.timeout && (clock_() - mark) >= record.timeout)
+                           return exit_error.value;
+                       break;
+
+               } // switch (record.control)
+
+           } while ( status == seq_status_t::CONTINUE);
+
+           return step; // step here is set by action_ as the return status
+       }
+};
+
+
+} //namespace utl;
+#endif /* utl_dev_dequencer_h__ */

include/utl/meta/typelist.h

@@ -244,7 +244,7 @@ namespace meta {
    //! @{
    namespace front_impl {
       template <typename L>
-      struct front_ { using type = nil_; };
+      struct front_ { };
 
       template <typename Head, typename... Tail>
       struct front_<typelist<Head, Tail...>> {
@@ -636,7 +636,7 @@ namespace meta {
 
    /*!
     * Search for the first \c Item on the \c List for which the predicate \c Pred
-    * yields to \c true_ when `eval<invoke<Pred, Item>>`
+    * returns true_ when `eval<invoke<Pred, Item>>`
     *
     * Complexity \f$ O(N) \f$
     *
@@ -684,7 +684,7 @@ namespace meta {
 
    /*!
     * Search for the first \c Item on the \c List for which the predicate \c Pred
-    * yields to \c true_ when `eval<invoke<Pred, Item>>` and return the rest of the \c List
+    * returns true_ when `eval<invoke<Pred, Item>>` and return the rest of the \c List
     * starting from that position as new typelist
     *
     * Complexity \f$ O(N) \f$
@@ -705,21 +705,8 @@ namespace meta {
    using seek = seek_if <List, same_as<T>>;
    //! @}
 
-   //! \name first_if
-   //! @{
-   /*!
-    * Search and returns the first \c Item on the \c List for which the predicate \c Pred
-    * yields to true_ when \code eval<invoke<Pred, Item>> \endcode
-    *
-    * Complexity \f$ O(N) \f$
-    *
-    * \tparam  List  A typelist
-    * \tparam  Pred  A Unary invocable predicate
-    * \return  On success the item, otherwise utl::meta::nil_
-    */
    template <typename List, typename Pred>
    using first_if = front<seek_if<List, Pred>>;
-   //! @}
 
    //! \name count_if
    //! @{
@@ -796,8 +783,8 @@ namespace meta {
    }
 
    /*!
-    * Returns a new typelist with elements, the elements of \c List that satisfy the
-    * invocable \c Pred such that `eval<invoke<Pred, Item>>` yields to \c true_
+    * Return a new typelist with elements, the elements of \c List that satisfy the
+    * invocable \c Pred such that `eval<invoke<Pred, Item>>` is \c true_
     *
     * Complexity \f$ O(N) \f$
     *

include/utl/utility/shared.h

@@ -0,0 +1,106 @@
+/*!
+ * \file utility/shared.h
+ * \brief
+ *      A CRTP base class to provide acquire/release functionality for shared resources
+ *      without handle pointers.
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ */
+
+#ifndef utl_utility_shared_h__
+#define utl_utility_shared_h__
+
+#include <utl/core/impl.h>
+
+#include <utility>
+
+namespace utl {
+
+/*!
+ * A CRTP base class to provide acquire/release functionality for shared resources
+ * without handle pointers.
+ *
+ * \example
+ * \code
+ * class GPIOClock : public shared<GPIOClock> {
+ *     friend shared<GPIOClock>;
+ *     void acquire_impl() { // HAL enable gpio clock }
+ *     void release_impl() { // HAL disable gpio clock }
+ * };
+ * GPIOClock clk;
+ * class Pin {
+ *     Pin() {
+ *         clk.acquire();
+ *         // init pin
+ *     }
+ *     ~Pin() {
+ *         // de-init pin
+ *         clk.release();
+ *     }
+ * };
+ * \endcode
+ *
+ * \tparam Impl_t   The derived class type
+ */
+template <typename Impl_t>
+class shared {
+        _CRTP_IMPL(Impl_t);
+        int count {};   //!< acquisition counter
+
+    protected:
+        shared() noexcept               = default;
+        shared(const shared&)           = delete;   //!< No copies
+        shared operator=(const shared&) = delete;   //!< No copies
+
+    public:
+        /*!
+         * Acquires the recourse. If it is the first call to acquire the resource we actually acquire it.
+         * Otherwise we just keep track of how many acquisition have made.
+         *
+         * \tparam Ts   The types of possible arguments
+         * \param args  Possible arguments to pass to acquire_impl() of derived class
+         */
+        template <typename ...Ts>
+        void acquire (Ts&&... args) {
+            if (!count++)   impl().acquire_impl(std::forward<Ts>(args)...);
+        }
+        /*!
+         * Release the recourse. On every call we decrease the count of acquisitions. If we reach zero
+         * we actually release the resource.
+         *
+         * \tparam Ts   The types of possible arguments
+         * \param args  Possible arguments to pass to release_impl() of derived class
+         */
+        template <typename ...Ts>
+        void release (Ts&&... args) noexcept {
+            if (--count <= 0) {
+                impl().release_impl(std::forward<Ts>(args)...);
+                count =0;
+            }
+        }
+};
+
+} // namespace utl;
+#endif /* utl_utility_shared_h__ */

test/tests/TmetaTypelist.cpp

@@ -174,9 +174,7 @@ namespace TmetaTypelist {
       EXPECT_EQ (true, (std::is_same<long, at<l, int_<3>>>()));
 
       EXPECT_EQ (true, (std::is_same<char*, front<l>>()));
-      EXPECT_EQ (true, (std::is_same<nil_, front<typelist<>>>()));
       EXPECT_EQ (true, (std::is_same<short, back<l>>()));
-      EXPECT_EQ (true, (std::is_same<nil_, back<typelist<>>>()));
    }
 
    TEST(TmetaTypelist, Concat) {

test/tests/cli_device.cpp

@@ -0,0 +1,422 @@
+/*!
+ * \file cli_device.cpp
+ *
+ * \copyright Copyright (C) 2020 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ *
+ */
+#include <utl/dev/cli_device.h>
+#include <gtest/gtest.h>
+
+#include <utl/container/equeue.h>
+
+#include <cstring>
+#include <utility>
+#include <type_traits>
+#ifndef WIN_TRHEADS
+#include <mutex>
+#include <thread>
+#else
+#include <mingw.thread.h>
+#include <mingw.mutex.h>
+#endif
+
+namespace test_cli_device {
+   using namespace utl;
+
+   // test settings
+   constexpr size_t Size  = 128;
+   using data_type        = char;
+
+   // cli_device implementer mock. We simulate a BG95 ATmodem for that purpose
+   template<size_t N>
+   class BG95 : public cli_device<BG95<N>, N> {
+	   using base_type = cli_device<BG95<N>, N>;
+	   using Queue     = equeue<typename base_type::value_type, N, true>;
+
+       public:
+           enum class event {
+               MQTT_DISCONNECT, MQTT_RXDATA
+           };
+       // simulated modem operation
+       private:
+           struct cmd_pair {
+               const char *cmd;
+               const char *resp;
+           };
+           struct event_pair {
+               event e;
+               const char* resp;
+           };
+
+           std::array<cmd_pair, 20> cmd_map = {{
+                   {"",                                             ""},
+                   {"ERROR",                                        "\r\nERROR\r\n"},
+                   {"ATE0\r\n",                                     "\r\nATE0\r\nOK\r\n"},
+                   {"AT\r\n",                                       "\r\nOK\r\n"},
+                   {"AT+QCFG=\"nwscanseq\"\r\n",                    "\r\n+QCFG: \"nwscanseq\",020301\r\n"},
+                   {"AT+QCFG=\"nwscanseq\",010302\r\n",             "\r\nOK\r\n"},
+                   {"AT+CREG?\r\n",                                 "\r\n+CREG: 0,5\r\n\r\nOK\r\n"},
+                   {"AT+CSQ\r\n",                                   "\r\n+CSQ: 19,99\r\n\r\nOK\r\n"},
+                   {"AT+QNWINFO\r\n",                               "\r\n+QNWINFO: \"EDGE\",\"20201\",\"GSM 1800\",865\r\n\r\nOK\r\n"},
+                   // Files
+                   {"AT+QFLST\r\n",                                 "\r\n+QFLST: \"cacert.pem\",1220\r\n+QFLST: \"security/\",2\r\nOK\r\n"},
+                   // MQTT config
+                   {"AT+QSSLCFG=\"ignorelocaltime\",2,1\r\n",       "\r\nOK\r\n"},
+                   {"AT+QSSLCFG=\"seclevel\",2,1\r\n",              "\r\nOK\r\n"},
+                   {"AT+QSSLCFG=\"sslversion\",2,4\r\n",            "\r\nOK\r\n"},
+                   {"AT+QSSLCFG=\"ciphersuite\",2\r\n",             "\r\n+QSSLCFG: \"ciphersuite\",2,0XFFFF\r\n\r\nOK\r\n"},
+                   {"AT+QMTCFG=\"ssl\",0,1,2\r\n",                  "\r\nOK\r\n"},
+                   {"AT+QMTCFG=\"keepalive\",0,3600\r\n",           "\r\nOK\r\n"},
+                   // MQTT
+                   {"AT+QMTOPEN=0,\"server.com\",8883\r\n",         "\r\nOK\r\n\r\n+QMTOPEN: 0,0\r\n"},
+                   {"AT+QMTCONN=0,\"myID\",\"user\",\"pass\"\r\n",  "\r\nOK\r\n\r\n+QMTCONN: 0,0,0\r\n"},
+                   {"AT+QMTSUB=0,1,\"/path/topic1\",2\r\n",         "\r\nOK\r\n\r\n+QMTSUB: 0,1,0,2\r\n"},
+                   {"AT+QMTPUB=0,0,0,0,\"/path/topic2\",9\r\n",     "\r\n> \r\nOK\r\n\r\n+QMTPUB: 0,0,0\r\n"},
+           }};
+           std::array<event_pair, 2> event_map {{
+                   {event::MQTT_DISCONNECT,     "\r\n+QMTSTAT: 0,1\r\n"},
+                   {event::MQTT_RXDATA,         "\r\n+QMTRECV: 0,1,\"/path/topic1\",\"BR: hello to all of my subscribers\""}
+           }};
+           const char* cmd_responce (const char* cmd) {
+               if (cmd != nullptr) {
+                   for (auto& it : cmd_map) {
+                       if (!std::strcmp(it.cmd, cmd))
+                           return it.resp;
+                   }
+               }
+               return cmd_map[1].resp;
+           }
+           const char* event_responce (const event e) {
+               for (auto& it : event_map) {
+                   if (e == it.e)
+                       return it.resp;
+               }
+               return nullptr;  // non reachable
+           }
+
+           // data
+           Queue RxQ{};
+           std::atomic<size_t> lines{};
+           clock_t t=0;
+
+       public:
+           // cli_device driver requirements
+           BG95() noexcept :
+               RxQ(Queue::data_match::MATCH_PUSH, base_type::delimiter, [&](){
+                   lines.fetch_add(1, std::memory_order_acq_rel);
+               }), lines(0) { }
+
+           size_t get(char* data, bool wait =false) {
+               do {
+                   if (lines.load(std::memory_order_acquire)) {
+                       size_t n =0;
+                       do{
+                           *data << RxQ;
+                           ++n;
+                       } while (*data++ != base_type::delimiter);
+                       lines.fetch_sub(1, std::memory_order_acq_rel);
+                       return n;
+                   }
+               } while (wait);
+               return 0;
+           }
+           size_t contents(char* data) {
+               char* nullpos = std::copy(RxQ.begin(), RxQ.end(), data);
+               *nullpos =0;
+               return nullpos - data;
+           }
+           size_t put (const char* data, size_t n) {
+               const char* reply = cmd_responce (data);
+               while (*reply)
+                   RxQ << *reply++;
+               return n;
+           }
+
+           clock_t clock() noexcept { return ++t; }
+           void clear_clock() noexcept { t=0; }
+
+           // extra helper for testing purposes
+           void async (event e) {
+               const char* reply =event_responce (e);
+               while (*reply)
+                   RxQ << *reply++;
+           }
+   };
+
+   // Behavior flag
+   bool handler_flag = false;
+   void handler (const char* data, size_t n) {
+       (void)*data;
+       (void)n;
+       handler_flag = true;
+   }
+   void clear_flag () {
+       handler_flag = false;
+   }
+
+   TEST(Tcli_device, traits) {
+       EXPECT_EQ ( std::is_default_constructible<BG95<Size>>::value, true);
+       EXPECT_EQ ( std::is_nothrow_default_constructible<BG95<Size>>::value, true);
+       EXPECT_EQ (!std::is_copy_constructible<BG95<Size>>::value, true);
+       EXPECT_EQ (!std::is_copy_assignable<BG95<Size>>::value, true);
+
+       EXPECT_EQ ((std::is_same_v<BG95<Size>::value_type, data_type>), true);
+       EXPECT_EQ ((std::is_same_v<BG95<Size>::pointer_type, data_type*>), true);
+       EXPECT_EQ ((std::is_same_v<BG95<Size>::size_type, size_t>), true);
+       EXPECT_EQ ((std::is_same_v<BG95<Size>::string_view, std::basic_string_view<data_type>>), true);
+
+   }
+
+   /*
+    * Test inetd in non blocking mode
+    */
+   TEST(Tcli_device, txrx_inetd) {
+       BG95<Size> modem;
+       char buffer[Size];
+       size_t s =0;
+
+       const BG95<Size>::inetd_handlers<2> async = {{
+           {"+QMTSTAT:", BG95<Size>::starts_with, handler},
+           {"+QMTRECV",  BG95<Size>::contains,    handler},
+       }};
+
+       s = modem.transmit("", std::strlen(""));
+       EXPECT_EQ (s, 0UL);
+       s = modem.transmit("");
+       EXPECT_EQ (s, 0UL);
+       s = modem.transmit(nullptr);
+       EXPECT_EQ (s, 0UL);
+
+       clear_flag();
+       modem.inetd(false, &async);
+       EXPECT_EQ (handler_flag, false);
+       modem.async(BG95<Size>::event::MQTT_DISCONNECT);
+       modem.inetd(false, &async);     // parse "\r\n"
+       EXPECT_EQ (handler_flag, false);
+       modem.inetd(false, &async);      // parse "+QMT*\r\n"  and dispatch to handler()
+       EXPECT_EQ (handler_flag, true);
+       clear_flag();                    // nothing to parse
+       modem.inetd(false, &async);
+       modem.inetd(false, &async);
+       modem.inetd(false, &async);
+       EXPECT_EQ (handler_flag, false);
+       EXPECT_NE (modem.receive(buffer), 0UL);  // "\r\n" in buffer
+       EXPECT_EQ (std::strcmp(buffer, "\r\n"), 0);
+
+       clear_flag();
+       modem.inetd(false, &async);
+       EXPECT_EQ (handler_flag, false);
+       modem.transmit("AT+CSQ\r\n", 8);
+       EXPECT_EQ (modem.receive(buffer), 0UL);
+       modem.inetd(false, &async);      // parse "\r\n"
+       EXPECT_NE (modem.receive(buffer), 0UL);
+       EXPECT_EQ (std::strcmp(buffer, "\r\n"), 0);
+       modem.inetd(false, &async);      // parse "+CSQ: 19,99\r\n"
+       EXPECT_NE (modem.receive(buffer), 0UL);
+       EXPECT_EQ (std::strcmp(buffer, "+CSQ: 19,99\r\n"), 0);
+       modem.inetd(false, &async);      // parse "\r\n"
+       EXPECT_NE (modem.receive(buffer), 0UL);
+       EXPECT_EQ (std::strcmp(buffer, "\r\n"), 0);
+       modem.inetd(false, &async);      // parse "OK\r\n"
+       EXPECT_NE (modem.receive(buffer), 0UL);
+       EXPECT_EQ (std::strcmp(buffer, "OK\r\n"), 0);
+       modem.inetd(false, &async);      // nothing to parse
+       modem.inetd(false, &async);
+       modem.inetd(false, &async);
+       EXPECT_EQ (modem.receive(buffer), 0UL);
+   }
+
+   TEST(Tcli_device, run) {
+       BG95<Size> modem;
+
+       using Control = BG95<Size>::control_t;
+
+       const BG95<Size>::script_t<4> script = {{
+           {Control::NOP,      "",          BG95<Size>::nil,         BG95<Size>::nil,  BG95<Size>::go_to<1>,   100000},
+           {Control::SEND,     "ATE0\r\n",  BG95<Size>::nil,         BG95<Size>::nil,  BG95<Size>::next,       0},
+           {Control::EXPECT,   "OK\r\n",    BG95<Size>::ends_with,   BG95<Size>::nil,  BG95<Size>::exit_ok,    100000},
+           {Control::OR_EXPECT,"ERROR",     BG95<Size>::contains,    BG95<Size>::nil,  BG95<Size>::exit_error, 0}
+       }};
+
+       std::mutex m;
+       m.lock();
+       std::thread th1 ([&](){
+           do
+               modem.inetd(false);
+           while (!m.try_lock());
+           m.unlock();
+       });
+       EXPECT_EQ (modem.run(script), BG95<Size>::exit_ok.value);
+       m.unlock();    // stop and join inetd
+       th1.join();
+   }
+
+   TEST(Tcli_device, clear_size) {
+       BG95<Size> modem;
+       char buffer[Size];
+
+       modem.clear();
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (modem.receive(buffer), 0UL);
+
+       modem.transmit("abcd", 4);
+       modem.inetd(false);
+       modem.inetd(false);
+       EXPECT_NE (modem.size(), 0UL);
+       modem.clear();
+       EXPECT_EQ (modem.size(), 0UL);
+
+   }
+
+   TEST(Tcli_device, command_non_extraction) {
+       BG95<Size> modem;
+       char buffer[Size];
+
+       std::mutex m;
+       m.lock();
+       std::thread th1 ([&](){
+           do
+               modem.inetd(false);
+           while (!m.try_lock());
+           m.unlock();
+       });
+
+       auto run_receive = [&](size_t times) -> size_t {
+           size_t s =0;
+           for (size_t i=0 ; i<times ; ++i)
+               s += modem.receive(buffer);
+           return s;
+       };
+
+       EXPECT_EQ (modem.command("", "", 0), true);          // returns: ""
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       EXPECT_EQ (modem.command("", "abcd", 100000), false);// returns: ""
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       EXPECT_EQ (modem.command("abcd", "", 0), true);      // returns: "\r\nERROR\r\n"
+       EXPECT_GT (run_receive(100000), 0UL);
+
+       EXPECT_EQ (modem.command("AT\r\n", "Something else", 100000), false);// returns: "\r\nOK\r\n"
+       EXPECT_GT (run_receive(100000), 0UL);
+
+       EXPECT_EQ (modem.command("AT\r\n", "\r\nOK\r\n", 100000), true);     // returns: "\r\nOK\r\n"
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       EXPECT_EQ (modem.command("AT\r\n", "%OK\r\n", 100000), true);        // returns: "\r\nOK\r\n"
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       // returns: "\r\n+CREG: 0,5\r\n\r\nOK\r\n
+       EXPECT_EQ (modem.command<BG95<Size>::flush>("AT+CREG?\r\n", "%OK\r\n", 0), false);
+       EXPECT_GT (run_receive(100000), 0UL);
+
+       // returns: "\r\n+CREG: 0,5\r\n\r\nOK\r\n
+       EXPECT_EQ (modem.command<BG95<Size>::flush>("AT+CREG?\r\n", "%%%OK\r\n", 0), true);
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       // returns: "\r\n+CREG: 0,5\r\n\r\nOK\r\n
+       EXPECT_EQ (modem.command<BG95<Size>::flush>("AT+CREG?\r\n", "%", 0), true);
+       EXPECT_GT (run_receive(100000), 0UL);
+
+       EXPECT_EQ (modem.command<BG95<Size>::flush>("AT\r\n", "%%", 0), true);   // returns: "\r\nOK\r\n"
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       EXPECT_EQ (modem.command<BG95<Size>::flush>("AT\r\n", "%%%", 10000), false); // returns: "\r\nOK\r\n"
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       // returns: "\r\n+CREG: 0,5\r\n\r\nOK\r\n
+       EXPECT_EQ (modem.command<modem.flush>("AT+CREG?\r\n", "", 0), true);
+       EXPECT_EQ (modem.command<modem.keep>("", "%", 0), true);
+       EXPECT_EQ (modem.command<modem.keep>("", "%%", 0), true);
+       EXPECT_EQ (modem.command<modem.keep>("", "%", 0), true);
+       EXPECT_EQ (modem.command<modem.keep>("", "%", 10000), false);
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       m.unlock();    // stop and join inetd
+       th1.join();
+   }
+
+   TEST(Tcli_device, command_extraction) {
+       BG95<Size> modem;
+       char buffer[Size];
+
+       std::mutex m;
+       m.lock();
+       std::thread th1 ([&](){
+           do
+               modem.inetd(false);
+           while (!m.try_lock());
+           m.unlock();
+       });
+
+       auto run_receive = [&](size_t times) -> size_t {
+           size_t s =0;
+           for (size_t i=0 ; i<times ; ++i)
+               s += modem.receive(buffer);
+           return s;
+       };
+
+       int status1, status2;
+       EXPECT_EQ (modem.command("AT+CREG?\r\n", "\r\n+CREG: 0,%\r\n\r\nOK\r\n", 100000, &status1), true);
+       EXPECT_EQ (status1, 5);
+       EXPECT_EQ (modem.command("AT+CREG?\r\n", "\r\n+CREG: %,%\r\n\r\nOK\r\n", 100000, &status1, &status2), true);
+       EXPECT_EQ (status1, 0);
+       EXPECT_EQ (status2, 5);
+
+       char substr1[32], substr2[32];
+       EXPECT_EQ (modem.command("AT+CREG?\r\n", "\r\n%\r\n\r\n%\r\n", 100000, substr1, substr2), true);
+       EXPECT_EQ (std::strcmp("+CREG: 0,5", substr1), 0);
+       EXPECT_EQ (std::strcmp("OK", substr2), 0);
+
+       // returns: "\r\n+CREG: 0,5\r\n\r\nOK\r\n
+       EXPECT_EQ (modem.command<modem.flush>("AT+CREG?\r\n", "", 100000), true);
+       EXPECT_EQ (modem.command<modem.keep>("", "%", 100000, substr1), true);
+       EXPECT_EQ (std::strcmp("\r\n", substr1), 0);
+
+       EXPECT_EQ (modem.command<modem.keep>("", "%%", 100000, substr1, substr2), true);
+       EXPECT_EQ (std::strcmp("+CREG: 0,5\r\n", substr1), 0);
+       EXPECT_EQ (std::strcmp("\r\n", substr2), 0);
+
+       EXPECT_EQ (modem.command<modem.keep>("", "%", 100000, substr1), true);
+       EXPECT_EQ (std::strcmp("OK\r\n", substr1), 0);
+
+       EXPECT_EQ (modem.command<modem.keep>("", "%", 10000), false);
+
+       EXPECT_EQ (modem.size(), 0UL);
+       EXPECT_EQ (run_receive(100000), 0UL);
+
+       m.unlock();    // stop and join inetd
+       th1.join();
+
+   }
+}

test/tests/deque.cpp

@@ -0,0 +1,469 @@
+/*!
+ * \file deque.cpp
+ * \brief
+ *      Unit tests for deque
+ *
+ * \copyright Copyright (C) 2020 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ *
+ */
+#include <utl/container/deque.h>
+//#include <utl/container/span.h>
+#include <gtest/gtest.h>
+
+#include <array>
+#include <type_traits>
+#include <cstring>
+#ifndef WIN_TRHEADS
+#include <mutex>
+#include <thread>
+#else
+#include <mingw.thread.h>
+#include <mingw.mutex.h>
+#endif
+
+namespace Tdeque {
+    using namespace utl;
+
+//    template <typename>
+//    struct is_span : std::false_type {};
+//
+//    template <typename T, std::size_t S>
+//    struct is_span<tbx::span<T, S>> : std::true_type {};
+
+    template <typename>
+    struct is_std_array : std::false_type {};
+
+    template <typename T, std::size_t N>
+    struct is_std_array<std::array<T, N>> : std::true_type {};
+
+    template <typename, typename = void>
+    struct has_size_and_data : std::false_type {};
+
+    template <typename T>
+    struct has_size_and_data<T, std::void_t<decltype(std::declval<T>().size()),
+                                            decltype(std::declval<T>().data())>>
+        : std::true_type {};
+
+    // Concept
+    TEST(Tdeque, concept) {
+        using deque_t = deque<int, 8>;
+
+        EXPECT_EQ ( std::is_default_constructible<deque_t>::value, true);
+        EXPECT_EQ ( std::is_nothrow_default_constructible<deque_t>::value, true);
+        EXPECT_EQ (!std::is_copy_constructible<deque_t>::value, true);
+        EXPECT_EQ (!std::is_copy_assignable<deque_t>::value, true);
+
+//        EXPECT_EQ (true, !is_span<deque_t>::value);
+        EXPECT_EQ (true, !is_std_array<deque_t>::value);
+        EXPECT_EQ (true, !std::is_array<deque_t>::value);
+        EXPECT_EQ (true,  has_size_and_data<deque_t>::value);
+    }
+    // Test construction
+    TEST(Tdeque, contruct) {
+        deque<int, 8> q1;
+        deque<int, 8> q2{1, 2, 3, 4, 5, 6, 7, 8};
+        deque<int, 8> q3{1, 2, 3, 4, 5};
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (8UL, q2.capacity());
+        EXPECT_EQ (8UL, q2.size());
+        EXPECT_EQ (8UL, q3.capacity());
+        EXPECT_EQ (5UL, q3.size());
+    }
+
+    // simple push-pop functionality
+    TEST(Tdeque, push_pop) {
+        deque<int, 8> q1;
+        deque<int, 8> q2{1, 2, 3, 4, 5, 6, 7, 8};
+
+        q1.push_front(1);
+        q1.push_front(2);
+        EXPECT_EQ (1, q1.pop_back());
+        EXPECT_EQ (2, q1.pop_back());
+
+        q1.push_back(1);
+        q1.push_back(2);
+        EXPECT_EQ (1, q1.pop_front());
+        EXPECT_EQ (2, q1.pop_front());
+
+        q1.push_front(2);
+        q1.push_back(3);
+        q1.push_front(1);
+        q1.push_back(4);
+
+        for (int i=1 ; i<= 4 ; ++i)
+            EXPECT_EQ ((int)i, q1.pop_front());
+    }
+
+    // front-back
+    TEST(Tdeque, front_back) {
+        deque<int, 8> q1;
+        deque<int, 8> q2{1, 2, 3, 4, 5, 6, 7, 8};
+
+        q1.push_front(2);
+        q1.push_front(1);
+        q1.push_back(3);
+        q1.push_back(4);
+
+        EXPECT_EQ (1, q1.front());
+        EXPECT_EQ (4, q1.back());
+        EXPECT_EQ (1, q2.front());
+        EXPECT_EQ (8, q2.back());
+    }
+
+    // capacity
+    TEST(Tdeque, capacity) {
+        deque<int, 8> q1;
+        deque<int, 8> q2{1, 2, 3, 4, 5, 6, 7, 8};
+
+        q1.push_back(1);
+        q1.clear();
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (true, q2.full());
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q2.capacity());
+
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (8UL, q2.size());
+
+        q1.push_back(2);
+        EXPECT_EQ (1UL, q1.size());
+        q1.push_front(1);
+        EXPECT_EQ (2UL, q1.size());
+
+        q1.pop_back();
+        EXPECT_EQ (1UL, q1.size());
+        q1.pop_front();
+        EXPECT_EQ (0UL, q1.size());
+    }
+
+    // push-pop limits
+    TEST (Tdeque, push_pop_limits) {
+        deque<int, 8> q1;
+        deque<int, 8> q2{1, 2, 3, 4, 5, 6, 7, 8};
+
+        EXPECT_EQ (int{}, q1.pop_back());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        EXPECT_EQ (int{}, q1.pop_front());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        q2.push_front(0);
+        EXPECT_EQ (1, q2.front());
+        EXPECT_EQ (8, q2.back());
+        EXPECT_EQ (8UL, q2.size());
+        EXPECT_EQ (false, q2.empty());
+        EXPECT_EQ (true, q2.full());
+
+        q2.push_back(9);
+        EXPECT_EQ (1, q2.front());
+        EXPECT_EQ (8, q2.back());
+        EXPECT_EQ (8UL, q2.size());
+        EXPECT_EQ (false, q2.empty());
+        EXPECT_EQ (true, q2.full());
+    }
+
+    // iterators
+    TEST (Tdeque, iterators) {
+        deque<int, 8> q1{1, 2, 3, 4, 5, 6, 7, 8};
+        int check_it=1;
+
+        EXPECT_EQ (q1.begin().base(), q1.end().base());
+        EXPECT_NE (q1.begin().iter(), q1.end().iter());
+        EXPECT_EQ (1, *q1.begin());
+        EXPECT_EQ (true, (q1.begin() == ++q1.end()));   // loop edge iterators
+
+        for (auto it = q1.begin() ; it != q1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(9, check_it);         // run through all
+
+        EXPECT_EQ (1, q1.front());      // queue stays intact
+        EXPECT_EQ (8, q1.back());
+        EXPECT_EQ (8UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (true, q1.full());
+
+        q1.pop_front();
+        q1.pop_back();
+
+        check_it=2;
+        for (auto& it : q1)
+            EXPECT_EQ(it, check_it++);
+        EXPECT_EQ(8, check_it);         // run through all
+
+        EXPECT_EQ (2, q1.front());      // queue stays intact
+        EXPECT_EQ (7, q1.back());
+        EXPECT_EQ (6UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        deque<int, 8> q2;
+        q2.push_front(2);
+        q2.push_front(1);
+        q2.push_back(3);
+        q2.push_back(4);
+        q2.push_back(5);
+        check_it =1;
+        for (auto& it : q2)
+            EXPECT_EQ(it, check_it++);
+        EXPECT_EQ(6, check_it);         // run through all
+
+    }
+    TEST (Tdeque, range) {
+        deque<int, 8> q1{1, 2, 3, 4, 5, 6, 7, 8};
+        int check_it=1;
+
+        for (auto& it : q1.contents())
+            EXPECT_EQ(it, check_it++);
+
+        EXPECT_EQ(9, check_it);         // run through all
+    }
+
+
+    // Concept
+    TEST(Tdeque, concept_atomic) {
+        using deque_t = deque<int, 8, true>;
+
+//        EXPECT_EQ (true, !is_span<deque_t>::value);
+        EXPECT_EQ (true, !is_std_array<deque_t>::value);
+        EXPECT_EQ (true, !std::is_array<deque_t>::value);
+        EXPECT_EQ (true,  has_size_and_data<deque_t>::value);
+    }
+    // Test construction
+    TEST(Tdeque, contruct_atomic) {
+        deque<int, 8, true> q1;
+        deque<int, 8, true> q2{1, 2, 3, 4, 5, 6, 7, 8};
+        deque<int, 8, true> q3{1, 2, 3, 4, 5};
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (8UL, q2.capacity());
+        EXPECT_EQ (8UL, q2.size());
+        EXPECT_EQ (8UL, q3.capacity());
+        EXPECT_EQ (5UL, q3.size());
+    }
+
+    // simple push-pop functionality
+    TEST(Tdeque, push_pop_atomic) {
+        deque<int, 8, true> q1;
+        deque<int, 8, true> q2{1, 2, 3, 4, 5, 6, 7, 8};
+
+        q1.push_front(1);
+        q1.push_front(2);
+        EXPECT_EQ (1, q1.pop_back());
+        EXPECT_EQ (2, q1.pop_back());
+
+        q1.push_back(1);
+        q1.push_back(2);
+        EXPECT_EQ (1, q1.pop_front());
+        EXPECT_EQ (2, q1.pop_front());
+
+        q1.push_front(2);
+        q1.push_back(3);
+        q1.push_front(1);
+        q1.push_back(4);
+
+        for (int i=1 ; i<= 4 ; ++i)
+            EXPECT_EQ ((int)i, q1.pop_front());
+    }
+
+    // front-back
+    TEST(Tdeque, front_back_atomic) {
+        deque<int, 8, true> q1;
+        deque<int, 8, true> q2{1, 2, 3, 4, 5, 6, 7, 8};
+
+        q1.push_front(2);
+        q1.push_front(1);
+        q1.push_back(3);
+        q1.push_back(4);
+
+        EXPECT_EQ (1, q1.front());
+        EXPECT_EQ (4, q1.back());
+        EXPECT_EQ (1, q2.front());
+        EXPECT_EQ (8, q2.back());
+    }
+
+    // capacity
+    TEST(Tdeque, capacity_atomic) {
+        deque<int, 8, true> q1;
+        deque<int, 8, true> q2{1, 2, 3, 4, 5, 6, 7, 8};
+
+        q1.push_back(1);
+        q1.clear();
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (true, q2.full());
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q2.capacity());
+
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (8UL, q2.size());
+
+        q1.push_back(2);
+        EXPECT_EQ (1UL, q1.size());
+        q1.push_front(1);
+        EXPECT_EQ (2UL, q1.size());
+
+        q1.pop_back();
+        EXPECT_EQ (1UL, q1.size());
+        q1.pop_front();
+        EXPECT_EQ (0UL, q1.size());
+    }
+
+    // push-pop limits
+    TEST (Tdeque, push_pop_limits_atomic) {
+        deque<int, 8, true> q1;
+        deque<int, 8, true> q2{1, 2, 3, 4, 5, 6, 7, 8};
+
+        EXPECT_EQ (int{}, q1.pop_back());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        EXPECT_EQ (int{}, q1.pop_front());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        q2.push_front(0);
+        EXPECT_EQ (1, q2.front());
+        EXPECT_EQ (8, q2.back());
+        EXPECT_EQ (8UL, q2.size());
+        EXPECT_EQ (false, q2.empty());
+        EXPECT_EQ (true, q2.full());
+
+        q2.push_back(9);
+        EXPECT_EQ (1, q2.front());
+        EXPECT_EQ (8, q2.back());
+        EXPECT_EQ (8UL, q2.size());
+        EXPECT_EQ (false, q2.empty());
+        EXPECT_EQ (true, q2.full());
+    }
+
+    // iterators
+    TEST (Tdeque, iterators_atomic) {
+        deque<int, 8, true> q1{1, 2, 3, 4, 5, 6, 7, 8};
+        int check_it=1;
+
+        EXPECT_EQ (q1.begin().base(), q1.end().base());
+        EXPECT_NE (q1.begin().iter(), q1.end().iter());
+        EXPECT_EQ (1, *q1.begin());
+        EXPECT_EQ (true, (q1.begin() == ++q1.end()));   // loop edge iterators
+
+        for (auto it = q1.begin() ; it != q1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(9, check_it);         // run through all
+
+        EXPECT_EQ (1, q1.front());      // queue stays intact
+        EXPECT_EQ (8, q1.back());
+        EXPECT_EQ (8UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (true, q1.full());
+
+        q1.pop_front();
+        q1.pop_back();
+
+        check_it=2;
+        for (auto& it : q1)
+            EXPECT_EQ(it, check_it++);
+        EXPECT_EQ(8, check_it);         // run through all
+
+        EXPECT_EQ (2, q1.front());      // queue stays intact
+        EXPECT_EQ (7, q1.back());
+        EXPECT_EQ (6UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        deque<int, 8, true> q2;
+        q2.push_front(2);
+        q2.push_front(1);
+        q2.push_back(3);
+        q2.push_back(4);
+        q2.push_back(5);
+        check_it =1;
+        for (auto& it : q2)
+            EXPECT_EQ(it, check_it++);
+        EXPECT_EQ(6, check_it);         // run through all
+
+    }
+    TEST (Tdeque, range_atomic) {
+        deque<int, 8, true> q1{1, 2, 3, 4, 5, 6, 7, 8};
+        int check_it=1;
+
+        for (auto& it : q1.contents())
+            EXPECT_EQ(it, check_it++);
+
+        EXPECT_EQ(9, check_it);         // run through all
+    }
+
+    TEST(Tdeque, race) {
+        constexpr size_t N = 1000000;
+        deque<int, N, true> q;
+        int result[N];
+
+        auto push_front = [&](){
+            for (size_t i=1 ; i<=N ; ++i)   q.push_front(i);
+        };
+        auto push_back = [&](){
+            for (size_t i=1 ; i<=N ; ++i)   q.push_back(i);
+        };
+        auto pop_front = [&](){
+            for (size_t i=0 ; i<N ; ) {
+                result[i] = q.pop_front();
+                if (result[i] != int{})
+                    ++i;
+            }
+        };
+        auto pop_back = [&](){
+            for (size_t i=0 ; i<N ; ) {
+                result[i] = q.pop_back();
+                if (result[i] != int{})
+                    ++i;
+            }
+        };
+
+        std::memset(result, 0, sizeof result);
+        std::thread th1 (push_front);
+        std::thread th2 (pop_back);
+        th1.join();
+        th2.join();
+        for (size_t i=0 ; i<N ; ++i)
+            EXPECT_EQ (result[i], (int)i+1);
+
+        std::memset(result, 0, sizeof result);
+        std::thread th3 (push_back);
+        std::thread th4 (pop_front);
+        th3.join();
+        th4.join();
+        for (size_t i=0 ; i<N ; ++i)
+            EXPECT_EQ (result[i], (int)i+1);
+    }
+}

test/tests/edeque.cpp

@@ -0,0 +1,555 @@
+/*!
+ * \file deque.cpp
+ * \brief
+ *      Unit tests for edeque
+ *
+ * \copyright Copyright (C) 2020 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ *
+ */
+#include <utl/container/edeque.h>
+#include <gtest/gtest.h>
+
+#include <functional>
+
+namespace Tedeque {
+    using namespace utl;
+
+    int global_flag =0;
+
+    // Callable mocks
+    void vfun(void) { ++global_flag; }
+
+    struct vfoo {
+       void operator() (void) { ++global_flag; }
+    };
+
+
+    TEST (Tedeque, construct) {
+        using Edeque = edeque<int, 8>;
+        struct T { int a,b; };
+        int local{};
+
+        Edeque e1(Edeque::size_match::GE, 3, [](){
+            ++global_flag;
+        });
+        Edeque e2(Edeque::size_match::GE, 3, [&](){
+            ++local;
+        });
+        Edeque e3(Edeque::size_match::EQ, 7, vfun);
+        edeque<T, 8> e4(edeque<T, 8>::size_match::EQ, 2, vfoo{});
+
+        edeque<int, 8> q1;
+        edeque<int, 8> q2(edeque<int, 8>::size_match::DISABLED, 0, nullptr);
+
+        EXPECT_EQ (8UL, e1.capacity());
+        EXPECT_EQ (8UL, e2.capacity());
+        EXPECT_EQ (8UL, e3.capacity());
+        EXPECT_EQ (8UL, e4.capacity());
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q2.capacity());
+    }
+
+    TEST (Tedeque, base_class) {
+        using Edeque = edeque<int, 8>;
+
+        Edeque e1(Edeque::size_match::GE, 3, [](){
+            ++global_flag;
+        });
+
+        // Access of base class functionality
+        EXPECT_EQ (8UL, e1.capacity());
+        EXPECT_EQ (0UL, e1.size());
+        EXPECT_EQ (true, e1.empty());
+        EXPECT_EQ (false, e1.full());
+
+        e1.push_back(7);
+        EXPECT_EQ (7, e1.front());
+        EXPECT_EQ (7, e1.back());
+        EXPECT_EQ (7, e1.pop_front());
+
+        e1.push_front(42);
+        EXPECT_EQ (42, e1.front());
+        EXPECT_EQ (42, e1.back());
+        EXPECT_EQ (42, e1.pop_back());
+
+        e1.push_back(1);
+        e1.push_back(2);
+        e1.push_back(3);
+
+        int check_it=1;
+        for (auto it = e1.begin() ; it != e1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(4, check_it);         // run through all
+    }
+
+    TEST (Tedeque, set_clear_check_trigger) {
+        using Edeque = edeque<int, 8>;
+        bool flag{};
+
+        Edeque e1(Edeque::size_match::GE, 1, [&](){ flag = true; });
+
+        flag = false;
+        e1.clear_trigger();
+        EXPECT_EQ (false, flag);
+        e1.push_back(1);            // 1,  no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        flag = false;
+        e1.clear();
+        e1.clear_trigger();
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e1.push_back(1);            // 1
+        e1.push_back(2);            // 2
+        e1.set_trigger(Edeque::size_match::GE, 1, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e1.check_trigger();         // manual trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        e1.check_trigger();         // manual trigger attempt
+        EXPECT_EQ (false, flag);    // [SIZE triggers are auto clear]
+
+        Edeque e2(Edeque::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+        flag = false;
+        e2.clear_trigger();
+        EXPECT_EQ (false, flag);
+        e2.push_back(42);           // push 42, no-trigger cleared
+        EXPECT_EQ (false, flag);
+        e2.set_trigger(Edeque::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e2.push_back(42);           // push 42, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        e2.push_back(42);           // push 42, re-trigger [DATA re-triggers]
+        EXPECT_EQ (true, flag);
+    }
+
+    TEST (Tedeque, size_triggers) {
+        using Edeque = edeque<int, 8>;
+        bool flag{};
+
+        // size_match::GE (size()>= 2)
+        Edeque ee(Edeque::size_match::GE, 2, [&](){ flag = true; });
+
+        flag = false;
+        ee.clear();
+        ee.push_back(1);            // 1
+        EXPECT_EQ (false, flag);
+        ee.push_back(2);            // 2, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.push_back(3);            // 3, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::GT (size()> 1)
+        flag = false;
+        ee.clear();
+        ee.set_trigger(Edeque::size_match::GT, 1, [&](){ flag = true; });
+        ee.push_back(1);            // 1
+        EXPECT_EQ (false, flag);
+        ee.push_back(2);            // 2, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.push_back(3);            // 3, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::LE (size()<= 1)
+        flag = false;
+        ee.clear();
+        ee.push_back(1);            // 1
+        ee.push_back(2);            // 2
+        ee.push_back(3);            // 3
+        ee.set_trigger(Edeque::size_match::LE, 1, [&](){ flag = true; });
+        ee.pop_front();             // 2
+        EXPECT_EQ (false, flag);
+        ee.pop_front();             // 1, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.pop_front();             // 0, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::LT (size()< 2)
+        flag = false;
+        ee.clear();
+        ee.push_back(1);            // 1
+        ee.push_back(2);            // 2
+        ee.push_back(3);            // 3
+        ee.set_trigger(Edeque::size_match::LT, 2, [&](){ flag = true; });
+        ee.pop_front();             // 2
+        EXPECT_EQ (false, flag);
+        ee.pop_front();             // 1, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.pop_front();             // 0, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::EQ (size()== 2)
+        flag = false;
+        ee.clear();
+        ee.set_trigger(Edeque::size_match::EQ, 2, [&](){ flag = true; });
+        ee.push_back(1);            // 1
+        EXPECT_EQ (false, flag);
+        ee.push_back(2);            // 2, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.push_back(3);            // 3
+        ee.pop_front();             // 2, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::NE (size()!= 0)
+        flag = false;
+        ee.clear();
+        ee.set_trigger(Edeque::size_match::NE, 0, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);
+        ee.push_back(1);            // 1, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.push_back(2);            // 2, no-trigger
+        EXPECT_EQ (false, flag);
+    }
+
+    TEST (Tedeque, data_triggers) {
+        using Edeque = edeque<int, 8>;
+        bool flag{};
+
+        // data_match::MATCH_PUSH (item == 42)
+        Edeque ee(Edeque::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+
+        flag = false;
+        ee.push_back(7);            // 7
+        EXPECT_EQ (false, flag);
+        ee.push_back(42);           // push:42, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        ee.pop_back();              // pop:42, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.push_back(42);           // push:42, re-trigger
+        EXPECT_EQ (true, flag);
+
+        // data_match::MATCH_POP (item == 42)
+        flag = false;
+        ee.clear_trigger();
+        ee.set_trigger(Edeque::data_match::MATCH_POP, 42, [&](){ flag = true; });
+        ee.push_back(7);            // 7
+        EXPECT_EQ (false, flag);
+        ee.push_back(42);           // push:42, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.pop_back();              // pop:42, trigger
+        EXPECT_EQ (true, flag);
+
+        // data_match::MISMATCH_PUSH (item != 42)
+        flag = false;
+        ee.clear();
+        ee.clear_trigger();
+        ee.push_back(7);            // 7
+        ee.set_trigger(Edeque::data_match::MISMATCH_PUSH, 42, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        ee.push_back(42);           // 42, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.push_back(0);            // 0, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        ee.push_back(1);            // 1, re-trigger
+        EXPECT_EQ (true, flag);
+
+        // data_match::MISMATCH_POP (item != 42)
+        flag = false;
+        ee.clear();
+        ee.clear_trigger();
+        ee.push_back(7);            // ->7
+        ee.pop_back();              // <-7
+        ee.set_trigger(Edeque::data_match::MISMATCH_POP, 42, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        ee.push_back(42);           // ->42, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.push_back(0);            // ->0, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.pop_back();              // pop:0, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        ee.push_back(0);
+        ee.pop_back();              // pop:0, re-trigger
+        EXPECT_EQ (true, flag);
+    }
+
+    // atomic
+    TEST (Tedeque, construct_atomic) {
+        using Edeque = edeque<int, 8, true>;
+        struct T { int a,b; };
+        int local{};
+
+        Edeque e1(Edeque::size_match::GE, 3, [](){
+            ++global_flag;
+        });
+        Edeque e2(Edeque::size_match::GE, 3, [&](){
+            ++local;
+        });
+        Edeque e3(Edeque::size_match::EQ, 7, vfun);
+        edeque<T, 8> e4(edeque<T, 8>::size_match::EQ, 2, vfoo{});
+
+        edeque<int, 8, true> q1;
+        edeque<int, 8, true> q2(edeque<int, 8, true>::size_match::DISABLED, 0, nullptr);
+
+        EXPECT_EQ (8UL, e1.capacity());
+        EXPECT_EQ (8UL, e2.capacity());
+        EXPECT_EQ (8UL, e3.capacity());
+        EXPECT_EQ (8UL, e4.capacity());
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q2.capacity());
+    }
+
+    TEST (Tedeque, base_class_atomic) {
+        using Edeque = edeque<int, 8, true>;
+
+        Edeque e1(Edeque::size_match::GE, 3, [](){
+            ++global_flag;
+        });
+
+        // Access of base class functionality
+        EXPECT_EQ (8UL, e1.capacity());
+        EXPECT_EQ (0UL, e1.size());
+        EXPECT_EQ (true, e1.empty());
+        EXPECT_EQ (false, e1.full());
+
+        e1.push_back(7);
+        EXPECT_EQ (7, e1.front());
+        EXPECT_EQ (7, e1.back());
+        EXPECT_EQ (7, e1.pop_front());
+
+        e1.push_front(42);
+        EXPECT_EQ (42, e1.front());
+        EXPECT_EQ (42, e1.back());
+        EXPECT_EQ (42, e1.pop_back());
+
+        e1.push_back(1);
+        e1.push_back(2);
+        e1.push_back(3);
+
+        int check_it=1;
+        for (auto it = e1.begin() ; it != e1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(4, check_it);         // run through all
+    }
+
+    TEST (Tedeque, set_clear_check_trigger_atomic) {
+        using Edeque = edeque<int, 8, true>;
+        bool flag{};
+
+        Edeque e1(Edeque::size_match::GE, 1, [&](){ flag = true; });
+
+        flag = false;
+        e1.clear_trigger();
+        EXPECT_EQ (false, flag);
+        e1.push_back(1);            // 1,  no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        flag = false;
+        e1.clear();
+        e1.clear_trigger();
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e1.push_back(1);            // 1
+        e1.push_back(2);            // 2
+        e1.set_trigger(Edeque::size_match::GE, 1, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e1.check_trigger();         // manual trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        e1.check_trigger();         // manual trigger attempt
+        EXPECT_EQ (false, flag);    // [SIZE triggers are auto clear]
+
+        Edeque e2(Edeque::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+        flag = false;
+        e2.clear_trigger();
+        EXPECT_EQ (false, flag);
+        e2.push_back(42);           // push 42, no-trigger cleared
+        EXPECT_EQ (false, flag);
+        e2.set_trigger(Edeque::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e2.push_back(42);           // push 42, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        e2.push_back(42);           // push 42, re-trigger [DATA re-triggers]
+        EXPECT_EQ (true, flag);
+    }
+
+    TEST (Tedeque, size_triggers_atomic) {
+        using Edeque = edeque<int, 8, true>;
+        bool flag{};
+
+        // size_match::GE (size()>= 2)
+        Edeque ee(Edeque::size_match::GE, 2, [&](){ flag = true; });
+
+        flag = false;
+        ee.clear();
+        ee.push_back(1);            // 1
+        EXPECT_EQ (false, flag);
+        ee.push_back(2);            // 2, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.push_back(3);            // 3, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::GT (size()> 1)
+        flag = false;
+        ee.clear();
+        ee.set_trigger(Edeque::size_match::GT, 1, [&](){ flag = true; });
+        ee.push_back(1);            // 1
+        EXPECT_EQ (false, flag);
+        ee.push_back(2);            // 2, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.push_back(3);            // 3, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::LE (size()<= 1)
+        flag = false;
+        ee.clear();
+        ee.push_back(1);            // 1
+        ee.push_back(2);            // 2
+        ee.push_back(3);            // 3
+        ee.set_trigger(Edeque::size_match::LE, 1, [&](){ flag = true; });
+        ee.pop_front();             // 2
+        EXPECT_EQ (false, flag);
+        ee.pop_front();             // 1, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.pop_front();             // 0, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::LT (size()< 2)
+        flag = false;
+        ee.clear();
+        ee.push_back(1);            // 1
+        ee.push_back(2);            // 2
+        ee.push_back(3);            // 3
+        ee.set_trigger(Edeque::size_match::LT, 2, [&](){ flag = true; });
+        ee.pop_front();             // 2
+        EXPECT_EQ (false, flag);
+        ee.pop_front();             // 1, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.pop_front();             // 0, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::EQ (size()== 2)
+        flag = false;
+        ee.clear();
+        ee.set_trigger(Edeque::size_match::EQ, 2, [&](){ flag = true; });
+        ee.push_back(1);            // 1
+        EXPECT_EQ (false, flag);
+        ee.push_back(2);            // 2, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.push_back(3);            // 3
+        ee.pop_front();             // 2, no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        // size_match::NE (size()!= 0)
+        flag = false;
+        ee.clear();
+        ee.set_trigger(Edeque::size_match::NE, 0, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);
+        ee.push_back(1);            // 1, trigger
+        EXPECT_EQ (true, flag);
+        flag = false;
+        ee.push_back(2);            // 2, no-trigger
+        EXPECT_EQ (false, flag);
+    }
+
+    TEST (Tedeque, data_triggers_atomic) {
+        using Edeque = edeque<int, 8, true>;
+        bool flag{};
+
+        // data_match::MATCH_PUSH (item == 42)
+        Edeque ee(Edeque::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+
+        flag = false;
+        ee.push_back(7);            // 7
+        EXPECT_EQ (false, flag);
+        ee.push_back(42);           // push:42, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        ee.pop_back();              // pop:42, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.push_back(42);           // push:42, re-trigger
+        EXPECT_EQ (true, flag);
+
+        // data_match::MATCH_POP (item == 42)
+        flag = false;
+        ee.clear_trigger();
+        ee.set_trigger(Edeque::data_match::MATCH_POP, 42, [&](){ flag = true; });
+        ee.push_back(7);            // 7
+        EXPECT_EQ (false, flag);
+        ee.push_back(42);           // push:42, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.pop_back();              // pop:42, trigger
+        EXPECT_EQ (true, flag);
+
+        // data_match::MISMATCH_PUSH (item != 42)
+        flag = false;
+        ee.clear();
+        ee.clear_trigger();
+        ee.push_back(7);            // 7
+        ee.set_trigger(Edeque::data_match::MISMATCH_PUSH, 42, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        ee.push_back(42);           // 42, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.push_back(0);            // 0, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        ee.push_back(1);            // 1, re-trigger
+        EXPECT_EQ (true, flag);
+
+        // data_match::MISMATCH_POP (item != 42)
+        flag = false;
+        ee.clear();
+        ee.clear_trigger();
+        ee.push_back(7);            // ->7
+        ee.pop_back();              // <-7
+        ee.set_trigger(Edeque::data_match::MISMATCH_POP, 42, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        ee.push_back(42);           // ->42, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.push_back(0);            // ->0, no-trigger
+        EXPECT_EQ (false, flag);
+        ee.pop_back();              // pop:0, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        ee.push_back(0);
+        ee.pop_back();              // pop:0, re-trigger
+        EXPECT_EQ (true, flag);
+    }
+}

test/tests/equeue.cpp

@@ -0,0 +1,317 @@
+/*!
+ * \file equeue.cpp
+ * \brief
+ *      Unit tests for equeue
+ *
+ * \copyright Copyright (C) 2020 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ *
+ */
+#include <utl/container/equeue.h>
+#include <gtest/gtest.h>
+
+namespace Tequeue {
+    using namespace utl;
+
+    int global_flag =0;
+
+    // Callable mocks
+    void vfun(void) { ++global_flag; }
+
+    struct vfoo {
+       void operator() (void) { ++global_flag; }
+    };
+
+    // Test construction
+    TEST(Tequeue, contruct) {
+        using Equeue = equeue<int, 8>;
+        struct T { int a,b; };
+        int local{};
+
+        Equeue e1(Equeue::size_match::GE, 3, [](){
+            ++global_flag;
+        });
+        Equeue e2(Equeue::size_match::GE, 3, [&](){
+            ++local;
+        });
+        Equeue e3(Equeue::size_match::EQ, 7, vfun);
+        equeue<T, 8> e4(equeue<T, 8>::size_match::EQ, 2, vfoo{});
+
+        equeue<int, 8> q1;
+        equeue<int, 8> q2(equeue<int, 8>::size_match::DISABLED, 0, nullptr);
+
+        EXPECT_EQ (8UL, e1.capacity());
+        EXPECT_EQ (8UL, e2.capacity());
+        EXPECT_EQ (8UL, e3.capacity());
+        EXPECT_EQ (8UL, e4.capacity());
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q2.capacity());
+    }
+
+    // simple push-pop functionality
+    TEST(Tequeue, base_class) {
+        using Equeue = equeue<int, 8>;
+
+        Equeue e1(Equeue::size_match::GE, 3, [](){
+            ++global_flag;
+        });
+
+        // Access of base class functionality
+        EXPECT_EQ (8UL, e1.capacity());
+        EXPECT_EQ (0UL, e1.size());
+        EXPECT_EQ (true, e1.empty());
+        EXPECT_EQ (false, e1.full());
+
+        e1.push(42);
+        EXPECT_EQ (42, e1.front());
+        EXPECT_EQ (42, e1.back());
+        EXPECT_EQ (42, e1.pop());
+
+        e1.push(1);
+        e1.push(2);
+        e1.push(3);
+
+        int check_it=1;
+        for (auto it = e1.begin() ; it != e1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(4, check_it);         // run through all
+
+    }
+
+    // trigger functionality
+    TEST (Tequeue, set_clear_check_trigger) {
+        using Equeue = equeue<int, 8>;
+        bool flag{};
+
+        Equeue e1(Equeue::size_match::GE, 1, [&](){ flag = true; });
+
+        flag = false;
+        e1.clear_trigger();
+        EXPECT_EQ (false, flag);
+        e1.push_back(1);            // 1,  no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        flag = false;
+        e1.clear();
+        e1.clear_trigger();
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e1.push_back(1);            // 1
+        e1.push_back(2);            // 2
+        e1.set_trigger(Equeue::size_match::GE, 1, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e1.check_trigger();         // manual trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        e1.check_trigger();         // manual trigger attempt
+        EXPECT_EQ (false, flag);    // [SIZE triggers are auto clear]
+
+        Equeue e2(Equeue::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+        flag = false;
+        e2.clear_trigger();
+        EXPECT_EQ (false, flag);
+        e2.push_back(42);           // push 42, no-trigger cleared
+        EXPECT_EQ (false, flag);
+        e2.set_trigger(Equeue::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e2.push_back(42);           // push 42, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        e2.push_back(42);           // push 42, re-trigger [DATA re-triggers]
+        EXPECT_EQ (true, flag);
+    }
+
+    // stream push-pop
+    TEST(Tequeue, stream_push_pop) {
+        equeue<int, 8> q1;
+
+        q1 << 1 << 2 << 3 << 4 << 5 << 6 << 7 << 8;
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (true, q1.full());
+
+        q1 << 9;                        // try to insert in full queue
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (true, q1.full());
+
+        int check_it=1;
+        for (auto it = q1.begin() ; it != q1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(9, check_it);         // run through all
+
+        for (int i =1 ; i <= 8 ; ++i) {
+            check_it << q1;
+            EXPECT_EQ(i, check_it);
+        }
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        q1 >> check_it;
+        EXPECT_EQ (int{}, check_it);
+    }
+
+    // atomic
+    // Test construction
+    TEST(Tequeue, contruct_atomic) {
+        using Equeue = equeue<int, 8, true>;
+        struct T { int a,b; };
+        int local{};
+
+        Equeue e1(Equeue::size_match::GE, 3, [](){
+            ++global_flag;
+        });
+        Equeue e2(Equeue::size_match::GE, 3, [&](){
+            ++local;
+        });
+        Equeue e3(Equeue::size_match::EQ, 7, vfun);
+        equeue<T, 8> e4(equeue<T, 8>::size_match::EQ, 2, vfoo{});
+
+        equeue<int, 8, true> q1;
+        equeue<int, 8, true> q2(equeue<int, 8, true>::size_match::DISABLED, 0, nullptr);
+
+        EXPECT_EQ (8UL, e1.capacity());
+        EXPECT_EQ (8UL, e2.capacity());
+        EXPECT_EQ (8UL, e3.capacity());
+        EXPECT_EQ (8UL, e4.capacity());
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q2.capacity());
+    }
+
+    // simple push-pop functionality
+    TEST(Tequeue, base_class_atomic) {
+        using Equeue = equeue<int, 8, true>;
+
+        Equeue e1(Equeue::size_match::GE, 3, [](){
+            ++global_flag;
+        });
+
+        // Access of base class functionality
+        EXPECT_EQ (8UL, e1.capacity());
+        EXPECT_EQ (0UL, e1.size());
+        EXPECT_EQ (true, e1.empty());
+        EXPECT_EQ (false, e1.full());
+
+        e1.push(42);
+        EXPECT_EQ (42, e1.front());
+        EXPECT_EQ (42, e1.back());
+        EXPECT_EQ (42, e1.pop());
+
+        e1.push(1);
+        e1.push(2);
+        e1.push(3);
+
+        int check_it=1;
+        for (auto it = e1.begin() ; it != e1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(4, check_it);         // run through all
+
+    }
+
+    // trigger functionality
+    TEST (Tequeue, set_clear_check_trigger_atomic) {
+        using Equeue = equeue<int, 8, true>;
+        bool flag{};
+
+        Equeue e1(Equeue::size_match::GE, 1, [&](){ flag = true; });
+
+        flag = false;
+        e1.clear_trigger();
+        EXPECT_EQ (false, flag);
+        e1.push_back(1);            // 1,  no-trigger cleared
+        EXPECT_EQ (false, flag);
+
+        flag = false;
+        e1.clear();
+        e1.clear_trigger();
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e1.push_back(1);            // 1
+        e1.push_back(2);            // 2
+        e1.set_trigger(Equeue::size_match::GE, 1, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e1.check_trigger();         // manual trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        e1.check_trigger();         // manual trigger attempt
+        EXPECT_EQ (false, flag);    // [SIZE triggers are auto clear]
+
+        Equeue e2(Equeue::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+        flag = false;
+        e2.clear_trigger();
+        EXPECT_EQ (false, flag);
+        e2.push_back(42);           // push 42, no-trigger cleared
+        EXPECT_EQ (false, flag);
+        e2.set_trigger(Equeue::data_match::MATCH_PUSH, 42, [&](){ flag = true; });
+        EXPECT_EQ (false, flag);    // no spurious triggers
+        e2.push_back(42);           // push 42, trigger
+        EXPECT_EQ (true, flag);
+
+        flag = false;
+        e2.push_back(42);           // push 42, re-trigger [DATA re-triggers]
+        EXPECT_EQ (true, flag);
+    }
+
+    // stream push-pop
+    TEST(Tequeue, stream_push_pop_atomic) {
+        equeue<int, 8, true> q1;
+
+        q1 << 1 << 2 << 3 << 4 << 5 << 6 << 7 << 8;
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (true, q1.full());
+
+        q1 << 9;                        // try to insert in full queue
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (true, q1.full());
+
+        int check_it=1;
+        for (auto it = q1.begin() ; it != q1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(9, check_it);         // run through all
+
+        for (int i =1 ; i <= 8 ; ++i) {
+            check_it << q1;
+            EXPECT_EQ(i, check_it);
+        }
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        q1 >> check_it;
+        EXPECT_EQ (int{}, check_it);
+    }
+
+}

test/tests/queue.cpp

@@ -0,0 +1,188 @@
+/*!
+ * \file queue.cpp
+ * \brief
+ *      Unit tests for queue
+ *
+ * \copyright Copyright (C) 2020 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ *
+ */
+#include <utl/container/queue.h>
+#include <gtest/gtest.h>
+
+namespace Tqueue {
+    using namespace utl;
+
+
+    // Test construction
+    TEST(Tqueue, contruct) {
+        queue<int, 8> q1;
+        queue<int, 8> q2{1, 2, 3, 4, 5, 6, 7, 8};
+        queue<int, 8> q3{1, 2, 3, 4, 5};
+
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (8UL, q2.capacity());
+        EXPECT_EQ (8UL, q2.size());
+        EXPECT_EQ (8UL, q3.capacity());
+        EXPECT_EQ (5UL, q3.size());
+    }
+
+    // base class functionality check
+    TEST(Tqueue, base_class) {
+
+        queue<int, 8> q1;
+
+        // Access of base class functionality
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        q1.push(42);
+        EXPECT_EQ (42, q1.front());
+        EXPECT_EQ (42, q1.back());
+        EXPECT_EQ (42, q1.pop());
+
+        q1.push(1);
+        q1.push(2);
+        q1.push(3);
+
+        int check_it=1;
+        for (auto it = q1.begin() ; it != q1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(4, check_it);         // run through all
+    }
+
+    // stream push-pop
+    TEST(Tqueue, stream_push_pop) {
+        queue<int, 8> q1;
+
+        q1 << 1 << 2 << 3 << 4 << 5 << 6 << 7 << 8;
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (true, q1.full());
+
+        q1 << 9;                        // try to insert in full queue
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (8UL, q1.size());
+        EXPECT_EQ (false, q1.empty());
+        EXPECT_EQ (true, q1.full());
+
+        int check_it=1;
+        for (auto it = q1.begin() ; it != q1.end() ; ++it)
+            EXPECT_EQ(*it, check_it++);
+        EXPECT_EQ(9, check_it);         // run through all
+
+        for (int i =1 ; i <= 8 ; ++i) {
+            check_it << q1;
+            EXPECT_EQ(i, check_it);
+        }
+        EXPECT_EQ (8UL, q1.capacity());
+        EXPECT_EQ (0UL, q1.size());
+        EXPECT_EQ (true, q1.empty());
+        EXPECT_EQ (false, q1.full());
+
+        q1 >> check_it;
+        EXPECT_EQ (int{}, check_it);
+    }
+
+
+
+    // Test construction
+     TEST(Tqueue, contruct_atomic) {
+         queue<int, 8, true> q1;
+         queue<int, 8, true> q2{1, 2, 3, 4, 5, 6, 7, 8};
+         queue<int, 8, true> q3{1, 2, 3, 4, 5};
+
+         EXPECT_EQ (8UL, q1.capacity());
+         EXPECT_EQ (0UL, q1.size());
+         EXPECT_EQ (8UL, q2.capacity());
+         EXPECT_EQ (8UL, q2.size());
+         EXPECT_EQ (8UL, q3.capacity());
+         EXPECT_EQ (5UL, q3.size());
+     }
+
+     // base class functionality check
+     TEST(Tqueue, base_class_atomic) {
+
+         queue<int, 8, true> q1;
+
+         // Access of base class functionality
+         EXPECT_EQ (8UL, q1.capacity());
+         EXPECT_EQ (0UL, q1.size());
+         EXPECT_EQ (true, q1.empty());
+         EXPECT_EQ (false, q1.full());
+
+         q1.push(42);
+         EXPECT_EQ (42, q1.front());
+         EXPECT_EQ (42, q1.back());
+         EXPECT_EQ (42, q1.pop());
+
+         q1.push(1);
+         q1.push(2);
+         q1.push(3);
+
+         int check_it=1;
+         for (auto it = q1.begin() ; it != q1.end() ; ++it)
+             EXPECT_EQ(*it, check_it++);
+         EXPECT_EQ(4, check_it);         // run through all
+     }
+
+     // stream push-pop
+     TEST(Tqueue, stream_push_pop_atomic) {
+         queue<int, 8, true> q1;
+
+         q1 << 1 << 2 << 3 << 4 << 5 << 6 << 7 << 8;
+         EXPECT_EQ (8UL, q1.capacity());
+         EXPECT_EQ (8UL, q1.size());
+         EXPECT_EQ (false, q1.empty());
+         EXPECT_EQ (true, q1.full());
+
+         q1 << 9;                        // try to insert in full queue
+         EXPECT_EQ (8UL, q1.capacity());
+         EXPECT_EQ (8UL, q1.size());
+         EXPECT_EQ (false, q1.empty());
+         EXPECT_EQ (true, q1.full());
+
+         int check_it=1;
+         for (auto it = q1.begin() ; it != q1.end() ; ++it)
+             EXPECT_EQ(*it, check_it++);
+         EXPECT_EQ(9, check_it);         // run through all
+
+         for (int i =1 ; i <= 8 ; ++i) {
+             check_it << q1;
+             EXPECT_EQ(i, check_it);
+         }
+         EXPECT_EQ (8UL, q1.capacity());
+         EXPECT_EQ (0UL, q1.size());
+         EXPECT_EQ (true, q1.empty());
+         EXPECT_EQ (false, q1.full());
+
+         q1 >> check_it;
+         EXPECT_EQ (int{}, check_it);
+     }
+
+}

test/tests/ring_iterator.cpp

@@ -0,0 +1,424 @@
+/*!
+ * \file ring_iterator.cpp
+ * \brief
+ *      Unit tests for ring_iterator
+ *
+ * \copyright Copyright (C) 2020 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ *
+ */
+#include <utl/container/ring_iterator.h>
+#include <gtest/gtest.h>
+
+#include <array>
+#include <type_traits>
+
+namespace Tring_iterator {
+    using namespace utl;
+
+    // Test construction
+    TEST(Tring_iterator, construct) {
+        int A[10];
+
+        //default constructor
+        ring_iterator<int*, 10> i1;
+        EXPECT_EQ(nullptr, i1.base());
+        EXPECT_EQ(nullptr, i1.iter());
+        EXPECT_EQ(10UL, i1.size());
+
+        // implementation specific (you can remove it freely)
+        EXPECT_EQ(2*sizeof(int*), sizeof(i1));
+
+        // basic
+        ring_iterator<int*, 10> i2(A);
+        EXPECT_EQ(A, i2.base());
+        EXPECT_EQ(A, i2.iter());
+        EXPECT_EQ(10UL, i2.size());
+
+        // basic from assignment
+        ring_iterator<int*, 10> i3 = A;
+        EXPECT_EQ(A, i3.base());
+        EXPECT_EQ(A, i3.iter());
+        EXPECT_EQ(10UL, i3.size());
+
+        // basic with offset
+        ring_iterator<int*, 10> i4(A, 5);
+        EXPECT_EQ(A, i4.base());
+        EXPECT_EQ(&A[5], i4.iter());
+        EXPECT_EQ(10UL, i4.size());
+
+        // copy (Legacy iterator)
+        auto i5 = i2;
+        EXPECT_EQ(A, i5.base());
+        EXPECT_EQ(A, i5.iter());
+        EXPECT_EQ(10UL, i5.size());
+
+        // arbitrary type
+        struct TT { int a,b,c; };
+        std::array<TT, 10> t;
+        ring_iterator<TT*, 10> it(t.data(), 2);
+        EXPECT_EQ(t.begin(), it.base());
+        EXPECT_EQ(&t[2], it.iter());
+        EXPECT_EQ(10UL, it.size());
+    }
+
+    // Legacy iterator
+    TEST(Tring_iterator, LegacyIterator) {
+
+        EXPECT_EQ(true, (std::is_same<int, typename ring_iterator<int*, 10>::value_type>::value));
+        EXPECT_EQ(true, (std::is_same<std::ptrdiff_t, typename ring_iterator<int*, 10>::difference_type>::value));
+        EXPECT_EQ(true, (std::is_same<int&, typename ring_iterator<int*, 10>::reference>::value));
+        EXPECT_EQ(true, (std::is_same<int*, typename ring_iterator<int*, 10>::pointer>::value));
+        EXPECT_EQ(true, (std::is_same<std::random_access_iterator_tag, typename ring_iterator<int*, 10>::iterator_category>::value));
+
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10> i1(A);
+
+        // copy constructible/assignable
+        auto i2 = i1;
+        EXPECT_EQ(A, i2.base());
+        EXPECT_EQ(A, i2.iter());
+        EXPECT_EQ(10UL, i2.size());
+
+        // dereferenceable - incrementable
+        ring_iterator<int*, 10> i3(A);
+        EXPECT_EQ(true, (std::is_reference<decltype(*i3)>::value));
+        EXPECT_EQ(true, (std::is_same<ring_iterator<int*, 10>&, decltype(++i3)>::value));
+        EXPECT_EQ(true, (std::is_reference<decltype((*i3++))>::value));
+
+        // more practical
+        ring_iterator<int*, 10> i4(A);
+        ring_iterator<int*, 10> i5(A, 9);
+        EXPECT_EQ(A[0], *i4);
+        EXPECT_EQ(&A[1], (++i4).iter());
+        // check loop
+        EXPECT_EQ(A[9], *i5);
+        EXPECT_EQ(&A[0], (++i5).iter());
+    }
+
+    // Legacy input iterator
+    TEST(Tring_iterator, LegacyInputIterator) {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10> i1(A), i2(A), i3(A, 1);
+
+        struct T { int m; };
+        T B[5] { {0}, {1}, {2}, {3}, {4}};
+        ring_iterator<T*, 5> it(B);
+
+        EXPECT_EQ (true, (std::is_same<bool, decltype(i1 == i2)>::value));
+        EXPECT_EQ (true, (std::is_same<bool, decltype(i1 != i2)>::value));
+        EXPECT_EQ (true, (std::is_same<int&, decltype(*i1)>::value));
+        EXPECT_EQ (true, (std::is_same<int, decltype(it->m)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10>&, decltype(++i1)>::value));
+        EXPECT_EQ (true, (std::is_same<int&, decltype(*i1++)>::value));
+
+        // more practical
+        EXPECT_EQ (true, i1 == i2);
+        EXPECT_EQ (true, i1 != i3);
+        EXPECT_EQ (0, *i1);
+        EXPECT_EQ (0, it->m);
+        EXPECT_EQ (true, (++i1 == i3));
+        EXPECT_EQ (1, *i1++);
+        EXPECT_EQ (2, *i1);
+    }
+
+    // Legacy input iterator
+    TEST(Tring_iterator, LegacyOutputIterator) {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10> it(A);
+
+        EXPECT_EQ (true, (std::is_assignable<decltype(*it), int>::value));
+        EXPECT_EQ (true, (std::is_assignable<decltype(*it++), int>::value));
+
+        // more practical
+        *it = 42;
+        EXPECT_EQ (42, A[0]);
+        *it++ = 7;
+        EXPECT_EQ (7, A[0]);
+        EXPECT_EQ (&A[1], it.iter());
+    }
+
+    // Legacy forward iterator
+    TEST(Tring_iterator, LegacyForwardIterator)
+     {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10> it(A);
+
+        EXPECT_EQ (0, *it++);
+        EXPECT_EQ (1, *it);
+    }
+
+    // Legacy bidirectional iterator
+    TEST(Tring_iterator, LegacyBidirectionalIterator) {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10> it(A);
+
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10>&, decltype(--it)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10>, decltype(it--)>::value));
+        EXPECT_EQ (true, (std::is_same<int&, decltype(*it--)>::value));
+
+        // more practical
+        ring_iterator<int*, 10> i1(A), i2(A, 9);
+        EXPECT_EQ (9, *i2--);   // check loop also
+        EXPECT_EQ (8, *i2);
+        EXPECT_EQ (0, *i1--);   // check loop also
+        EXPECT_EQ (9, *i1);
+    }
+
+    // Legacy random access iterator
+    TEST(Tring_iterator, LegacyRandomAccessIterator) {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10> it1(A), it2(A, 7);
+
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10>&, decltype(it1 += 7)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10>, decltype(it1 + 7)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10>, decltype(7 + it1)>::value));
+
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10>&, decltype(it1 -= 7)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10>, decltype(it1 - 7)>::value));
+
+        EXPECT_EQ (true, (std::is_same<std::ptrdiff_t, decltype(it1 - it2)>::value));
+        EXPECT_EQ (true, (std::is_same<int&, decltype(it1[7])>::value));
+
+        EXPECT_EQ (true, (std::is_same<bool, decltype(it1 < it2)>::value));
+        EXPECT_EQ (true, (std::is_same<bool, decltype(it1 > it2)>::value));
+        EXPECT_EQ (true, (std::is_same<bool, decltype(it1 <= it2)>::value));
+        EXPECT_EQ (true, (std::is_same<bool, decltype(it1 >= it2)>::value));
+
+        // more practical
+        ring_iterator<int*, 10> i1(A), i2(A);
+        i1 += 7;
+        EXPECT_EQ (7, *i1);
+        i1 -= 7;
+        EXPECT_EQ (0, *i1);
+        i1 += 11;
+        EXPECT_EQ (1, *i1);
+        i1 -= 2;
+        EXPECT_EQ (9, *i1);
+
+        EXPECT_EQ (7, *(i2+7));
+        EXPECT_EQ (7, *(7+i2));
+        EXPECT_EQ (1, *(i2+11));
+        EXPECT_EQ (1, *(11+i2));
+        EXPECT_EQ (7, *(i1-2));
+        EXPECT_EQ (8, *(i2-2));
+
+        EXPECT_EQ (9, (i1 - i2));
+        EXPECT_EQ (1, (i2 - i1));   // loop
+
+    }
+
+    // Test construction atomic
+    TEST(Tring_iterator, construct_atomic) {
+        int A[10];
+
+        //default constructor
+        ring_iterator<int*, 10, true> i1;
+        EXPECT_EQ(nullptr, i1.base());
+        EXPECT_EQ(nullptr, i1.iter());
+        EXPECT_EQ(10UL, i1.size());
+
+        // implementation specific (you can remove it freely)
+        EXPECT_EQ(2*sizeof(int*), sizeof(i1));
+
+        // basic
+        ring_iterator<int*, 10, true> i2(A);
+        EXPECT_EQ(A, i2.base());
+        EXPECT_EQ(A, i2.iter());
+        EXPECT_EQ(10UL, i2.size());
+
+        // basic from assignment
+        ring_iterator<int*, 10, true> i3 = A;
+        EXPECT_EQ(A, i3.base());
+        EXPECT_EQ(A, i3.iter());
+        EXPECT_EQ(10UL, i3.size());
+
+        // basic with offset
+        ring_iterator<int*, 10, true> i4(A, 5);
+        EXPECT_EQ(A, i4.base());
+        EXPECT_EQ(&A[5], i4.iter());
+        EXPECT_EQ(10UL, i4.size());
+
+        // copy (Legacy iterator)
+        auto i5 = i2;
+        EXPECT_EQ(A, i5.base());
+        EXPECT_EQ(A, i5.iter());
+        EXPECT_EQ(10UL, i5.size());
+
+        // arbitrary type
+        struct TT { int a,b,c; };
+        std::array<TT, 10> t;
+        ring_iterator<TT*, 10, true> it(t.data(), 2);
+        EXPECT_EQ(t.begin(), it.base());
+        EXPECT_EQ(&t[2], it.iter());
+        EXPECT_EQ(10UL, it.size());
+    }
+
+    // Legacy iterator atomic
+    TEST(Tring_iterator, LegacyIterator_atomic) {
+
+        EXPECT_EQ(true, (std::is_same<int, typename ring_iterator<int*, 10, true>::value_type>::value));
+        EXPECT_EQ(true, (std::is_same<std::ptrdiff_t, typename ring_iterator<int*, 10, true>::difference_type>::value));
+        EXPECT_EQ(true, (std::is_same<int&, typename ring_iterator<int*, 10, true>::reference>::value));
+        EXPECT_EQ(true, (std::is_same<int*, typename ring_iterator<int*, 10, true>::pointer>::value));
+        EXPECT_EQ(true, (std::is_same<std::random_access_iterator_tag, typename ring_iterator<int*, 10, true>::iterator_category>::value));
+
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10, true> i1(A);
+
+        // copy constructible/assignable
+        auto i2 = i1;
+        EXPECT_EQ(A, i2.base());
+        EXPECT_EQ(A, i2.iter());
+        EXPECT_EQ(10UL, i2.size());
+
+        // dereferenceable - incrementable
+        ring_iterator<int*, 10, true> i3(A);
+        EXPECT_EQ(true, (std::is_reference<decltype(*i3)>::value));
+        EXPECT_EQ(true, (std::is_same<ring_iterator<int*, 10, true>&, decltype(++i3)>::value));
+        EXPECT_EQ(true, (std::is_reference<decltype((*i3++))>::value));
+
+        // more practical
+        ring_iterator<int*, 10, true> i4(A);
+        ring_iterator<int*, 10, true> i5(A, 9);
+        EXPECT_EQ(A[0], *i4);
+        EXPECT_EQ(&A[1], (++i4).iter());
+        // check loop
+        EXPECT_EQ(A[9], *i5);
+        EXPECT_EQ(&A[0], (++i5).iter());
+    }
+
+    // Legacy input iterator atomic
+    TEST(Tring_iterator, LegacyInputIterator_atomic) {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10, true> i1(A), i2(A), i3(A, 1);
+
+        struct T { int m; };
+        T B[5] { {0}, {1}, {2}, {3}, {4}};
+        ring_iterator<T*, 5, true> it(B);
+
+        EXPECT_EQ (true, (std::is_same<bool, decltype(i1 == i2)>::value));
+        EXPECT_EQ (true, (std::is_same<bool, decltype(i1 != i2)>::value));
+        EXPECT_EQ (true, (std::is_same<int&, decltype(*i1)>::value));
+        EXPECT_EQ (true, (std::is_same<int, decltype(it->m)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10, true>&, decltype(++i1)>::value));
+        EXPECT_EQ (true, (std::is_same<int&, decltype(*i1++)>::value));
+
+        // more practical
+        EXPECT_EQ (true, i1 == i2);
+        EXPECT_EQ (true, i1 != i3);
+        EXPECT_EQ (0, *i1);
+        EXPECT_EQ (0, it->m);
+        EXPECT_EQ (true, (++i1 == i3));
+        EXPECT_EQ (1, *i1++);
+        EXPECT_EQ (2, *i1);
+    }
+
+    // Legacy input iterator atomic
+    TEST(Tring_iterator, LegacyOutputIterator_atomic) {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10, true> it(A);
+
+        EXPECT_EQ (true, (std::is_assignable<decltype(*it), int>::value));
+        EXPECT_EQ (true, (std::is_assignable<decltype(*it++), int>::value));
+
+        // more practical
+        *it = 42;
+        EXPECT_EQ (42, A[0]);
+        *it++ = 7;
+        EXPECT_EQ (7, A[0]);
+        EXPECT_EQ (&A[1], it.iter());
+    }
+
+    // Legacy forward iterator atomic
+    TEST(Tring_iterator, LegacyForwardIterator_atomic)
+     {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10, true> it(A);
+
+        EXPECT_EQ (0, *it++);
+        EXPECT_EQ (1, *it);
+    }
+
+    // Legacy bidirectional iterator atomic
+    TEST(Tring_iterator, LegacyBidirectionalIterator_atomic) {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10, true> it(A);
+
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10, true>&, decltype(--it)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10, true>, decltype(it--)>::value));
+        EXPECT_EQ (true, (std::is_same<int&, decltype(*it--)>::value));
+
+        // more practical
+        ring_iterator<int*, 10, true> i1(A), i2(A, 9);
+        EXPECT_EQ (9, *i2--);   // check loop also
+        EXPECT_EQ (8, *i2);
+        EXPECT_EQ (0, *i1--);   // check loop also
+        EXPECT_EQ (9, *i1);
+    }
+
+    // Legacy random access iterator atomic
+    TEST(Tring_iterator, LegacyRandomAccessIterator_atomic) {
+        int A[10] {0, 1, 2, 3, 4, 5, 6, 7, 8 , 9};
+        ring_iterator<int*, 10, true> it1(A), it2(A, 7);
+
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10, true>&, decltype(it1 += 7)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10, true>, decltype(it1 + 7)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10, true>, decltype(7 + it1)>::value));
+
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10, true>&, decltype(it1 -= 7)>::value));
+        EXPECT_EQ (true, (std::is_same<ring_iterator<int*, 10, true>, decltype(it1 - 7)>::value));
+
+        EXPECT_EQ (true, (std::is_same<std::ptrdiff_t, decltype(it1 - it2)>::value));
+        EXPECT_EQ (true, (std::is_same<int&, decltype(it1[7])>::value));
+
+        EXPECT_EQ (true, (std::is_same<bool, decltype(it1 < it2)>::value));
+        EXPECT_EQ (true, (std::is_same<bool, decltype(it1 > it2)>::value));
+        EXPECT_EQ (true, (std::is_same<bool, decltype(it1 <= it2)>::value));
+        EXPECT_EQ (true, (std::is_same<bool, decltype(it1 >= it2)>::value));
+
+        // more practical
+        ring_iterator<int*, 10, true> i1(A), i2(A);
+        i1 += 7;
+        EXPECT_EQ (7, *i1);
+        i1 -= 7;
+        EXPECT_EQ (0, *i1);
+        i1 += 11;
+        EXPECT_EQ (1, *i1);
+        i1 -= 2;
+        EXPECT_EQ (9, *i1);
+
+        EXPECT_EQ (7, *(i2+7));
+        EXPECT_EQ (7, *(7+i2));
+        EXPECT_EQ (1, *(i2+11));
+        EXPECT_EQ (1, *(11+i2));
+        EXPECT_EQ (7, *(i1-2));
+        EXPECT_EQ (8, *(i2-2));
+
+        EXPECT_EQ (9, (i1 - i2));
+        EXPECT_EQ (1, (i2 - i1));   // loop
+
+    }
+
+}

test/tests/sequencer.cpp

@@ -0,0 +1,451 @@
+/*!
+ * \file sequencer.cpp
+ *
+ * \copyright Copyright (C) 2020 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ * </dd></dl>
+ *
+ */
+#include <utl/dev/sequencer.h>
+#include <gtest/gtest.h>
+
+#include <type_traits>
+#include <cstring>
+#include <ctime>
+
+namespace test_sequencer {
+   using namespace utl;
+
+   // test settings
+   using data_type        = char;
+   constexpr size_t size  = 64;
+
+   // Sequencer implementer mock
+   class Seq : public sequencer<Seq, data_type, size> {
+       static constexpr int NrCommands =5;
+       static constexpr int NoCommand  =-1;
+
+       std::array<const char*, NrCommands> command = {
+           "cmd1",
+           "cmd2\n",
+           "cmd3\r\n",
+           "cmd4\n\r",
+           "cmd5\n",
+       };
+       std::array<const char*, NrCommands> reply {
+           "reply1",
+           "reply2\n",
+           "reply3\n text \r text text\n",
+           "reply4\n text\n text \r text\r\n",
+           "reply5\n",
+       };
+       int cmd =NoCommand;
+       clock_t t =0;
+
+       public:
+           size_t get(char* data) {
+               static int ans = 0;
+               if ((++ans % 3) == 0)
+                   return 0;
+
+               if (cmd == NoCommand) {
+                   std::strcpy(data, "ERROR\n");
+                   return 6;
+               } else {
+                   std::strcpy(data, reply[cmd]);
+                   size_t s = std::strlen(reply[cmd]);
+                   cmd =NoCommand;
+                   return s;
+               }
+           }
+           size_t contents (char* data) {
+               if (cmd == NoCommand) {
+                   std::strcpy(data, "");
+                   return 0;
+               } else {
+                   std::strcpy(data, reply[cmd]);
+                   return std::strlen(reply[cmd]);
+               }
+           }
+           size_t put (const char* data, size_t n) {
+               for (size_t i =0 ; i<NrCommands ; ++i) {
+                   if (!std::strcmp(data, command[i])) {
+                       cmd =i;
+                       return n;
+                   }
+               }
+               cmd =NoCommand;
+               return n;
+           }
+           clock_t clock() { return ++t; }
+           void clear_clock() { t =0; }
+   };
+
+   /*
+    * Test  sequencer object
+    */
+   TEST (Tsequencer, traits) {
+       EXPECT_EQ ( std::is_default_constructible<Seq>::value, true);
+       EXPECT_EQ ( std::is_nothrow_default_constructible<Seq>::value, true);
+       EXPECT_EQ (!std::is_copy_constructible<Seq>::value, true);
+       EXPECT_EQ (!std::is_copy_assignable<Seq>::value, true);
+
+       EXPECT_EQ ((std::is_same_v<Seq::value_type, data_type>), true);
+       EXPECT_EQ ((std::is_same_v<Seq::pointer_type, data_type*>), true);
+       EXPECT_EQ ((std::is_same_v<Seq::size_type, size_t>), true);
+       EXPECT_EQ ((std::is_same_v<Seq::string_view, std::basic_string_view<data_type>>), true);
+
+       Seq s;
+       EXPECT_EQ (s.size(), size);
+   }
+
+   TEST (Tsequencer, predicates) {
+       EXPECT_EQ ((std::is_invocable_r<bool, decltype(Seq::equals), Seq::string_view, Seq::string_view>::value), true);
+       EXPECT_EQ ((std::is_invocable_r<bool, decltype(Seq::starts_with), Seq::string_view, Seq::string_view>::value), true);
+       EXPECT_EQ ((std::is_invocable_r<bool, decltype(Seq::ends_with), Seq::string_view, Seq::string_view>::value), true);
+       EXPECT_EQ ((std::is_invocable_r<bool, decltype(Seq::contains), Seq::string_view, Seq::string_view>::value), true);
+       EXPECT_EQ ((std::is_invocable_r<bool, decltype(Seq::always_true), Seq::string_view, Seq::string_view>::value), true);
+       EXPECT_EQ ((std::is_invocable_r<bool, decltype(Seq::always_false), Seq::string_view, Seq::string_view>::value), true);
+
+       EXPECT_EQ (Seq::nil, nullptr);
+   }
+
+   TEST (Tsequencer, actions) {
+       EXPECT_EQ ( std::is_default_constructible<Seq::action_t>::value, true);
+       EXPECT_EQ ( std::is_nothrow_default_constructible<Seq::action_t>::value, true);
+       EXPECT_EQ ( std::is_copy_constructible<Seq::action_t>::value, true);
+       EXPECT_EQ ( std::is_copy_assignable<Seq::action_t>::value, true);
+
+       EXPECT_EQ ((std::is_same_v<const Seq::action_t, decltype(Seq::no_action)>), true);
+       EXPECT_EQ ((std::is_same_v<const Seq::action_t, decltype(Seq::next)>), true);
+       EXPECT_EQ ((std::is_same_v<const Seq::action_t, decltype(Seq::exit_ok)>), true);
+       EXPECT_EQ ((std::is_same_v<const Seq::action_t, decltype(Seq::exit_error)>), true);
+
+       EXPECT_EQ ((std::is_same_v<const Seq::action_t, decltype(Seq::go_to<0>)>), true);
+       EXPECT_EQ ((std::is_same_v<const Seq::action_t, decltype(Seq::exit<0>)>), true);
+   }
+
+   bool handler_flag = false;
+   const char* text = "abc";
+
+   //static bool check_handle (const str_view_t buffer, const str_view_t token, match_ft match, handler_ft handle)
+   TEST(Tsequencer, check_handle) {
+       Seq s;
+//       foo (5);
+//       bar (5);
+       using str_t = Seq::string_view;
+       using val_t = Seq::value_type;
+
+       auto match    = [](const str_t x, const str_t y) ->bool { (void)x; (void)y; return true; };
+       auto no_match = [](const str_t x, const str_t y) ->bool { (void)x; (void)y; return false; };
+       auto check_match = [] (const str_t x, const str_t y) ->bool {
+           return x == y;
+       };
+       auto handler    = [](const val_t* v, size_t s){ (void)*v; (void)s; handler_flag = true; };
+       auto set_if_abc = [](const val_t* v, size_t s){
+           (void)*v; (void)s;
+           handler_flag = (str_t(v, s) == "abc");
+       };
+
+       EXPECT_EQ (s.check_handle("", "", nullptr, nullptr), false);
+       EXPECT_EQ (s.check_handle("", "", no_match, nullptr), false);
+       EXPECT_EQ (s.check_handle("", "", match, nullptr), false);
+
+       handler_flag = false;
+       EXPECT_EQ (s.check_handle("", "", no_match, handler), false);
+       EXPECT_EQ (handler_flag, false);
+
+       handler_flag = false;
+       EXPECT_EQ (s.check_handle("", "", match, handler), true);
+       EXPECT_EQ (handler_flag, true);
+
+       handler_flag = false;
+       EXPECT_EQ (s.check_handle("abcd", "abc", check_match, set_if_abc), false);
+       EXPECT_EQ (handler_flag, false);
+
+       handler_flag = false;
+       EXPECT_EQ (s.check_handle("abc", "abc", check_match, set_if_abc), true);
+       EXPECT_EQ (handler_flag, true);
+
+       handler_flag = false;
+       EXPECT_EQ (s.check_handle("abc", "abcd", check_match, set_if_abc), false);
+       EXPECT_EQ (handler_flag, false);
+
+   }
+
+   TEST(Tsequencer, run_nop_and_exits) {
+       Seq s;
+       const Seq::script_t<1> script1 = {{
+           {Seq::control_t::NOP,  "", Seq::nil, Seq::nil, Seq::exit_ok, 1000}
+       }};
+       s.clear_clock();
+       EXPECT_EQ (s.run(script1), Seq::exit_ok.value);
+       EXPECT_GE (s.clock(), (clock_t)1000);
+
+       const Seq::script_t<1> script2 = {{
+           {Seq::control_t::NOP,  "", Seq::nil, Seq::nil, Seq::exit_error, 1000}
+       }};
+       s.clear_clock();
+       EXPECT_EQ (s.run(script2), Seq::exit_error.value);
+       EXPECT_GE (s.clock(), (clock_t)1000);
+
+       const Seq::script_t<3> script3 = {{
+           {Seq::control_t::NOP,  "", Seq::nil, Seq::nil, Seq::next, 1000},
+           {Seq::control_t::NOP,  "", Seq::nil, Seq::nil, Seq::next, 1000},
+           {Seq::control_t::NOP,  "", Seq::nil, Seq::nil, Seq::exit_ok, 1000}
+       }};
+       s.clear_clock();
+       EXPECT_EQ (s.run(script3), Seq::exit_ok.value);
+       EXPECT_GE (s.clock(), (clock_t)3000);
+   }
+
+   TEST(Tsequencer, run_send) {
+       Seq s;
+
+       auto send_wrapper  = [](const data_type* d, size_t s){
+           (void)*d; (void)s; handler_flag = true;
+       };
+       auto send_chk_text = [](const data_type* d, size_t s){
+           handler_flag = (Seq::string_view(d,s) == Seq::string_view(text));
+       };
+
+       const Seq::script_t<2> script1 = {{
+           {Seq::control_t::SEND, "", Seq::nil, Seq::nil,     Seq::next, 0},
+           {Seq::control_t::SEND, "", Seq::nil, send_wrapper, Seq::exit_ok, 0}
+       }};
+       handler_flag =false;
+       EXPECT_EQ (s.run(script1), Seq::exit_ok.value);
+       EXPECT_EQ (handler_flag, true);
+
+
+       const Seq::script_t<1> script2 = {{
+           {Seq::control_t::SEND, "abcd", Seq::nil, send_chk_text, Seq::exit_ok, 0}
+       }};
+       handler_flag =false;
+       EXPECT_EQ (s.run(script2), Seq::exit_ok.value);
+       EXPECT_EQ (handler_flag, false);
+
+       const Seq::script_t<2> script3 = {{
+           {Seq::control_t::SEND, text, Seq::nil, send_chk_text, Seq::exit_ok, 0}
+       }};
+       handler_flag =false;
+       EXPECT_EQ (s.run(script3), Seq::exit_ok.value);
+       EXPECT_EQ (handler_flag, true);
+   }
+
+   TEST(Tsequencer, run_expect) {
+       Seq s;
+
+       const Seq::script_t<7> script = {{
+           {Seq::control_t::EXPECT,    "reply1",   Seq::equals,      Seq::nil,  Seq::exit<1UL>,    1000},
+           {Seq::control_t::OR_EXPECT, "reply2",   Seq::starts_with, Seq::nil,  Seq::exit<2UL>,    0},
+           {Seq::control_t::OR_EXPECT, "reply3",   Seq::starts_with, Seq::nil,  Seq::exit<3UL>,    0},
+           {Seq::control_t::OR_EXPECT, "reply4\n", Seq::starts_with, Seq::nil,  Seq::exit<4UL>,    0},
+           {Seq::control_t::OR_EXPECT, "reply5",   Seq::starts_with, Seq::nil,  Seq::exit<5UL>,    0},
+           {Seq::control_t::OR_EXPECT, "ERROR",    Seq::contains,    Seq::nil,  Seq::exit<6UL>,    0},
+           {Seq::control_t::NOP,       "",         Seq::nil,         Seq::nil,  Seq::exit_error,   1000}
+       }};
+
+       s.clear_clock();
+       s.put("cmd1", std::strlen("cmd1"));
+       EXPECT_EQ (s.run(script), 1UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd2\n", std::strlen("cmd2\n"));
+       EXPECT_EQ (s.run(script), 2UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd3\r\n", std::strlen("cmd3\r\n"));
+       EXPECT_EQ (s.run(script), 3UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd4\n\r", std::strlen("cmd4\n\r"));
+       EXPECT_EQ (s.run(script), 4UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd5\n", std::strlen("cmd5\n"));
+       EXPECT_EQ (s.run(script), 5UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd", std::strlen("cmd"));
+       EXPECT_EQ (s.run(script), 6UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+   }
+
+   TEST(Tsequencer, run_detect) {
+       Seq s;
+
+       const Seq::script_t<7> script = {{
+           {Seq::control_t::DETECT,    "reply1",   Seq::equals,      Seq::nil,  Seq::exit<1UL>,    1000},
+           {Seq::control_t::OR_DETECT, "reply2",   Seq::starts_with, Seq::nil,  Seq::exit<2UL>,    0},
+           {Seq::control_t::OR_DETECT, "reply3",   Seq::starts_with, Seq::nil,  Seq::exit<3UL>,    0},
+           {Seq::control_t::OR_DETECT, "reply4\n", Seq::starts_with, Seq::nil,  Seq::exit<4UL>,    0},
+           {Seq::control_t::OR_DETECT, "reply5",   Seq::starts_with, Seq::nil,  Seq::exit<5UL>,    0},
+           {Seq::control_t::OR_DETECT, "ERROR",    Seq::contains,    Seq::nil,  Seq::exit<6UL>,    0},
+           {Seq::control_t::NOP,       "",         Seq::nil,         Seq::nil,  Seq::exit_ok,      1000}
+       }};
+
+       s.clear_clock();
+       s.put("cmd1", std::strlen("cmd1"));
+       EXPECT_EQ (s.run(script), 1UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd2\n", std::strlen("cmd2\n"));
+       EXPECT_EQ (s.run(script), 2UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd3\r\n", std::strlen("cmd3\r\n"));
+       EXPECT_EQ (s.run(script), 3UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd4\n\r", std::strlen("cmd4\n\r"));
+       EXPECT_EQ (s.run(script), 4UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd5\n", std::strlen("cmd5\n"));
+       EXPECT_EQ (s.run(script), 5UL);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+
+       s.clear_clock();
+       s.put("cmd", std::strlen("cmd"));
+       EXPECT_EQ (s.run(script), Seq::exit_error.value);
+       EXPECT_GT (s.clock(), (clock_t)1000);
+   }
+
+   TEST(Tsequencer, run_script_blocks_n_gotos) {
+       Seq s;
+       const Seq::script_t<15> script = {{
+           /* 0 */{Seq::control_t::NOP,       "",         Seq::nil,         Seq::nil,   Seq::go_to<1>,   1000},
+
+           /* 1 */{Seq::control_t::SEND,      "cmd1",     Seq::nil,         Seq::nil,   Seq::next,       0},
+           /* 2 */{Seq::control_t::EXPECT,    "reply1",   Seq::starts_with, Seq::nil,   Seq::next,       1000},
+           /* 3 */{Seq::control_t::OR_EXPECT, "ERROR",    Seq::contains,    Seq::nil,   Seq::exit_error, 0},
+
+           /* 4 */{Seq::control_t::SEND,      "cmd2\n",   Seq::nil,         Seq::nil,   Seq::next,       0},
+           /* 5 */{Seq::control_t::DETECT,    "ERROR",    Seq::contains,    Seq::nil,   Seq::exit_error, 1000},
+           /* 6 */{Seq::control_t::OR_DETECT, "reply2",   Seq::contains,    Seq::nil,   Seq::go_to<11>,  0},
+
+           /* 7 */{Seq::control_t::SEND,      "cmd3\r\n", Seq::nil,         Seq::nil,  Seq::next,        0},
+           /* 8 */{Seq::control_t::EXPECT,    "ERROR",    Seq::contains,    Seq::nil,  Seq::exit_error,  1000},
+           /* 9 */{Seq::control_t::OR_EXPECT, "lalala",   Seq::starts_with, Seq::nil,  Seq::exit_error,  0},
+           /*10 */{Seq::control_t::OR_EXPECT, "text\n",   Seq::ends_with,   Seq::nil,  Seq::go_to<14>,   0},
+
+           /*11 */{Seq::control_t::SEND,      "cmd4\n\r", Seq::nil,         Seq::nil,  Seq::next,        0},
+           /*12 */{Seq::control_t::EXPECT,    "reply4\n", Seq::starts_with, Seq::nil,  Seq::go_to<7>,    1000},
+           /*13 */{Seq::control_t::OR_EXPECT, "ERROR",    Seq::contains,    Seq::nil,  Seq::exit_error,  0},
+
+           /*14 */{Seq::control_t::NOP,       "",         Seq::nil,         Seq::nil,  Seq::exit_ok,     1000}
+       }};
+       s.clear_clock();
+       EXPECT_EQ (s.run(script), Seq::exit_ok.value);
+       EXPECT_GT (s.clock(), (clock_t)2000);
+   }
+
+   TEST(Tsequencer, run_match_n_handler) {
+       Seq s;
+
+       using str_t = Seq::string_view;
+       using val_t = Seq::value_type;
+
+       auto match    = [](const str_t x, const str_t y) ->bool { (void)x; (void)y; return true; };
+       auto check_match = [] (const str_t x, const str_t y) ->bool {
+           return x == y;
+       };
+       auto handler     = [](const val_t* v, size_t s){ (void)*v; (void)s; handler_flag = true; };
+       auto set_if_rpl2 = [](const val_t* v, size_t s){
+           (void)*v; (void)s;
+           handler_flag = (str_t(v, s) == "reply2\n");
+       };
+
+       const Seq::script_t<4> script1 = {{
+           {Seq::control_t::SEND,      "cmd1",   Seq::nil,        Seq::nil,   Seq::next,       0},
+           {Seq::control_t::EXPECT,    "",       match,           Seq::nil,   Seq::next,       1000},
+           {Seq::control_t::OR_EXPECT, "ERROR",  Seq::contains,   Seq::nil,   Seq::exit_error, 0},
+
+           {Seq::control_t::SEND,      "cmd1",   Seq::nil,        handler,    Seq::exit_ok,    0}
+       }};
+       handler_flag = false;
+       s.clear_clock();
+       EXPECT_EQ (s.run(script1), Seq::exit_ok.value);
+       EXPECT_LT (s.clock(), (clock_t)1000);
+       EXPECT_EQ (handler_flag, true);
+
+       const Seq::script_t<2> script2 = {{
+           {Seq::control_t::SEND,      "cmd1",   Seq::nil,        Seq::nil,    Seq::next,       0},
+           {Seq::control_t::EXPECT,    "reply1", check_match,     set_if_rpl2, Seq::exit_ok,    1000},
+       }};
+       handler_flag = false;
+       EXPECT_EQ (s.run(script2), Seq::exit_ok.value);
+       EXPECT_EQ (handler_flag, false);
+
+       const Seq::script_t<2> script3 = {{
+           {Seq::control_t::SEND,      "cmd2\n",   Seq::nil,      Seq::nil,    Seq::next,       0},
+           {Seq::control_t::EXPECT,    "reply2\n", check_match,   set_if_rpl2, Seq::exit_ok,    1000},
+       }};
+       handler_flag = false;
+       EXPECT_EQ (s.run(script3), Seq::exit_ok.value);
+       EXPECT_EQ (handler_flag, true);
+
+       const Seq::script_t<1> script4 = {{
+           {Seq::control_t::SEND, "cmd1", Seq::nil, handler, Seq::exit_ok, 0}
+       }};
+       handler_flag = false;
+       EXPECT_EQ (s.run(script4), Seq::exit_ok.value);
+       EXPECT_EQ (handler_flag, true);
+   }
+
+   TEST(Tsequencer, run_boundaries) {
+       Seq s;
+
+       const Seq::script_t<1> script1 = {{
+           {Seq::control_t::NOP,  "", Seq::nil, Seq::nil, Seq::next, 0},
+       }};
+       EXPECT_EQ (s.run(script1), Seq::exit_error.value);
+
+       const Seq::script_t<1> script2 = {{
+           {Seq::control_t::NOP,  "", Seq::nil, Seq::nil, Seq::go_to<1>, 0},
+       }};
+       EXPECT_EQ (s.run(script2), Seq::exit_error.value);
+
+       const Seq::script_t<1> script3 = {{
+           {Seq::control_t::NOP,  "", Seq::nil, Seq::nil, Seq::go_to<(size_t)-1>, 0},
+       }};
+       EXPECT_EQ (s.run(script3), Seq::exit_error.value);
+
+       const Seq::script_t<1> script4 = {{
+           {Seq::control_t::EXPECT,  "abc", Seq::nil, Seq::nil, Seq::next, 1000},
+       }};
+       s.clear_clock();
+       EXPECT_EQ (s.run(script4), Seq::exit_error.value);
+       EXPECT_GT (s.clock(), (clock_t)1000);
+   }
+}