tbx/include/cont/deque.h

/*!
 * \file cont/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 TBX_CONT_DEQUE_H_
#define TBX_CONT_DEQUE_H_

#include <core/core.h>
#include <core/ring_iterator.h>

#include <array>

namespace tbx {

/*!
 * \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
 */
template <typename Data_t, size_t N>
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>;

        // 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()} { }

        //! fill contructor
        constexpr deque(const Data_t& value) noexcept {
            data_.fill(value);
            f = iterator(data_.data(), N);
            r = iterator(data_.data(), N);
        }

        //! 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)) { }

        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               { return f+1; }
        constexpr const_iterator begin() const noexcept   { return f+1; }
        constexpr const_iterator cbegin() const noexcept  { return f+1; }

        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                { return f+1; }
        constexpr const_reverse_iterator rend() const noexcept    { return f+1; }
        constexpr const_reverse_iterator crend() const noexcept   { return f+1; }
    //! @}

    //! \name Capacity
    //! @{
    public:
        //! \return The size of the deque. The items currently in queue.
        constexpr size_t size() noexcept {
            return full() ? N: (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 (r == f) ? 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());
        }
        //! \brief      Push an item in the front of the deque
        //! \param it   The item to push
        constexpr void push_front (const Data_t& it) {
            if (full())     return;
            *f-- = it;
        }
        //! \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 () {
            if (empty())    return Data_t{};
            return *++f;
        }
        //! \brief      Push an item in the back of the deque
        //! \param it   The item to push
        constexpr void push_back (const Data_t& it) {
            if (full())     return;
            *r++ = it;
        }
        //! \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 () {
            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 { return *(f+1); }
        constexpr const Data_t& front() const noexcept { return *(f+1); }

        //! \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 { return *(r-1); }
        constexpr const Data_t& back() const noexcept { return *(r-1); }

    //! @}
    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).
};

}

#endif /* TBX_CONT_ADEQUE_H_ */