DEV: a a json lazy decoder

include/tbx.h

@@ -37,6 +37,7 @@
 #include <cont/queue.h>
 #include <cont/equeue.h>
 
+#include <utils/json.h>
 #include <utils/shared.h>
 #include <utils/print.h>
 #include <utils/timer_delay.h>

include/utils/json.h

@@ -0,0 +1,202 @@
+/*!
+ * \file files.h
+ * \brief
+ *      File functionality header
+ *
+ * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
+ *
+ * <dl class=\"section copyright\"><dt>License</dt><dd>
+ * All Rights Reserved.
+ *
+ * NOTICE:  All information contained herein is, and remains
+ * the property of Christos Choutouridis. The intellectual
+ * and technical concepts contained herein are proprietary to
+ * Christos Choutouridis and are protected by copyright law.
+ * Dissemination of this information or reproduction of this material
+ * is strictly forbidden unless prior written permission is obtained
+ * from Christos Choutouridis.
+ * </dd></dl>
+ */
+#ifndef JSON_H_
+#define JSON_H_
+
+#include <cstddef>
+#include <cstdlib>
+#include <cstring>
+#include <cctype>
+#include <type_traits>
+#include <string_view>
+#include <array>
+
+using size_t = std::size_t;
+
+struct jpair_t {
+    std::string_view key;
+    std::string_view value;
+};
+
+template<size_t N>
+struct json_dec_t {
+
+    using string_view = std::string_view;
+
+    json_dec_t(const char* buffer, size_t size) noexcept :
+    buffer_(buffer, size), valid_(true) {
+        enum state_t {
+            ST=0, KEY, COLON, VALUE, SP
+        } state = ST;
+
+        size_t pairs =0;
+        char* begin = nullptr;
+        int s =0;
+        for (size_t i=0 ; i<size ; ++i) {
+            switch (state) {
+                case ST:
+                    if (std::isspace(buffer[i]))
+                        continue;   // skip white space
+                    if (buffer[i] == '{')
+                        state = KEY;
+                    break;
+
+                case KEY:
+                    if (pairs >= N) {
+                        valid_ = false;
+                        break;
+                    }
+                    if (std::isspace(buffer[i]))
+                        continue;   // skip white space
+                    if (buffer[i] == '\"') {
+                        if (!begin)
+                            begin = (char*)&buffer[i+1];
+                        else {
+                            s = (char*)&buffer[i] - begin;
+                            if (s > 0)
+                                pairs_[pairs].key = std::string_view{begin, (size_t)s};
+                            else
+                                pairs_[pairs].key = std::string_view{};
+                            begin =nullptr;
+                            s =0;
+                            state = COLON;
+                        }
+                    }
+                    else if (buffer[i] == '}')
+                        return;
+                    break;
+
+                case COLON:
+                    if (std::isspace(buffer[i]))
+                        continue;   // skip white space
+                    if (buffer[i] == ':')
+                        state = VALUE;
+                    else {
+                        valid_ = false;
+                        return;
+                    }
+                    break;
+
+                case VALUE:
+                    if (pairs >= N) {
+                        valid_ = false;
+                        break;
+                    }
+                    if (!begin && std::isspace(buffer[i]))
+                        continue;
+                    else if (!begin && !std::isspace(buffer[i]))
+                        begin = (buffer[i] != '\"') ? (char*)&buffer[i] : (char*)&buffer[i+1];
+                    else if (begin && (std::isspace(buffer[i]) || buffer[i] == ',' || buffer[i] == '}')) {
+                        s  = (char*)&buffer[i] - begin;
+                        s -= (buffer[i-1] == '\"') ? 1:0;
+                        if (s > 0)
+                            pairs_[pairs].value = std::string_view{begin, (size_t)s};
+                        else
+                            pairs_[pairs].value = std::string_view{};
+                        ++pairs;
+                        begin =nullptr;
+                        s =0;
+                        if (std::isspace(buffer[i]))
+                            state = SP;
+                        else if (buffer[i] == ',')
+                            state = KEY;
+                        else if (buffer[i] == '}')
+                            return;
+                    }
+                    break;
+
+                case SP:
+                    if (std::isspace(buffer[i]))
+                        continue;   // skip white space
+                    else if (buffer[i] == ',')
+                        state = KEY;
+                    else if (buffer[i] == '}')
+                        return;
+                    else {
+                        valid_ = false;
+                        return;
+                    }
+                    break;
+            }
+        }
+    }
+    template<typename T>
+    T get (const char* key) {
+        T t{};
+        for (auto& it : pairs_) {
+            if (it.key.compare(key) == 0) {
+                extract_(it.value, &t);
+                break;
+            }
+        }
+        return t;
+    }
+    bool is_valid() const { return valid_; }
+
+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
+     */
+    void extract_(std::string_view str, bool* value) {
+        *value = (
+            !std::strncmp(str.data(), "true", str.size()) ||
+            !std::strncmp(str.data(), "True", str.size()) ||
+            !std::strncmp(str.data(), "TRUE", str.size()) ||
+            !std::strncmp(str.data(), "1", str.size())
+        ) ? true : false;
+    }
+    void extract_(std::string_view str, int* value) {
+        *value = std::atoi(str.data());
+    }
+    void extract_(std::string_view str, unsigned int* value) {
+        *value = (unsigned int)std::atoi(str.data());
+    }
+    void extract_(std::string_view str, long* value) {
+        *value = std::atol(str.data());
+    }
+    void extract_(std::string_view str, unsigned long* value) {
+        *value = (unsigned long)std::atol(str.data());
+    }
+    void extract_(std::string_view str, double* value) {
+        *value = std::atof(str.data());
+    }
+    void extract_(std::string_view str, char** value) {
+        *value = (char*)str.data();
+    }
+    void extract_(std::string_view str, string_view* value) {
+        *value = str;
+    }
+    //! Specialization (as overload function) to handle void* types
+    void extract_ (const char* str, void* value) noexcept {
+        (void)*str; (void)value;
+    }
+private:
+    std::string_view        buffer_;
+    std::array<jpair_t, N>  pairs_;
+    bool                    valid_;
+};
+
+
+
+#endif /* JSON_H_ */