DEV: a a json lazy decoder
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@ -37,6 +37,7 @@
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#include <cont/queue.h>
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#include <cont/equeue.h>
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#include <utils/json.h>
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#include <utils/shared.h>
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#include <utils/print.h>
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#include <utils/timer_delay.h>
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202
include/utils/json.h
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202
include/utils/json.h
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/*!
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* \file files.h
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* \brief
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* File functionality header
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*
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* \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
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*
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* <dl class=\"section copyright\"><dt>License</dt><dd>
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* All Rights Reserved.
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*
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* NOTICE: All information contained herein is, and remains
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* the property of Christos Choutouridis. The intellectual
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* and technical concepts contained herein are proprietary to
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* Christos Choutouridis and are protected by copyright law.
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* Dissemination of this information or reproduction of this material
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* is strictly forbidden unless prior written permission is obtained
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* from Christos Choutouridis.
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* </dd></dl>
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*/
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#ifndef JSON_H_
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#define JSON_H_
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#include <cstddef>
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#include <cstdlib>
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#include <cstring>
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#include <cctype>
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#include <type_traits>
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#include <string_view>
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#include <array>
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using size_t = std::size_t;
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struct jpair_t {
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std::string_view key;
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std::string_view value;
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};
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template<size_t N>
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struct json_dec_t {
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using string_view = std::string_view;
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json_dec_t(const char* buffer, size_t size) noexcept :
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buffer_(buffer, size), valid_(true) {
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enum state_t {
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ST=0, KEY, COLON, VALUE, SP
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} state = ST;
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size_t pairs =0;
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char* begin = nullptr;
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int s =0;
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for (size_t i=0 ; i<size ; ++i) {
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switch (state) {
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case ST:
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if (std::isspace(buffer[i]))
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continue; // skip white space
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if (buffer[i] == '{')
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state = KEY;
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break;
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case KEY:
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if (pairs >= N) {
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valid_ = false;
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break;
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}
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if (std::isspace(buffer[i]))
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continue; // skip white space
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if (buffer[i] == '\"') {
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if (!begin)
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begin = (char*)&buffer[i+1];
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else {
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s = (char*)&buffer[i] - begin;
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if (s > 0)
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pairs_[pairs].key = std::string_view{begin, (size_t)s};
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else
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pairs_[pairs].key = std::string_view{};
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begin =nullptr;
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s =0;
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state = COLON;
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}
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}
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else if (buffer[i] == '}')
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return;
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break;
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case COLON:
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if (std::isspace(buffer[i]))
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continue; // skip white space
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if (buffer[i] == ':')
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state = VALUE;
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else {
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valid_ = false;
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return;
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}
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break;
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case VALUE:
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if (pairs >= N) {
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valid_ = false;
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break;
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}
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if (!begin && std::isspace(buffer[i]))
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continue;
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else if (!begin && !std::isspace(buffer[i]))
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begin = (buffer[i] != '\"') ? (char*)&buffer[i] : (char*)&buffer[i+1];
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else if (begin && (std::isspace(buffer[i]) || buffer[i] == ',' || buffer[i] == '}')) {
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s = (char*)&buffer[i] - begin;
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s -= (buffer[i-1] == '\"') ? 1:0;
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if (s > 0)
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pairs_[pairs].value = std::string_view{begin, (size_t)s};
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else
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pairs_[pairs].value = std::string_view{};
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++pairs;
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begin =nullptr;
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s =0;
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if (std::isspace(buffer[i]))
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state = SP;
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else if (buffer[i] == ',')
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state = KEY;
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else if (buffer[i] == '}')
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return;
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}
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break;
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case SP:
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if (std::isspace(buffer[i]))
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continue; // skip white space
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else if (buffer[i] == ',')
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state = KEY;
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else if (buffer[i] == '}')
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return;
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else {
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valid_ = false;
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return;
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}
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break;
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}
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}
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}
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template<typename T>
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T get (const char* key) {
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T t{};
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for (auto& it : pairs_) {
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if (it.key.compare(key) == 0) {
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extract_(it.value, &t);
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break;
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}
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}
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return t;
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}
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bool is_valid() const { return valid_; }
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private:
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/*!
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* Convert the text pointed by \c str to a value and store it to
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* \c value. The type of conversion is deduced by the compiler
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* \tparam T The type of the value
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* \param str pointer to string with the value
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* \param value pointer to converted value
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*/
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void extract_(std::string_view str, bool* value) {
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*value = (
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!std::strncmp(str.data(), "true", str.size()) ||
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!std::strncmp(str.data(), "True", str.size()) ||
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!std::strncmp(str.data(), "TRUE", str.size()) ||
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!std::strncmp(str.data(), "1", str.size())
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) ? true : false;
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}
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void extract_(std::string_view str, int* value) {
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*value = std::atoi(str.data());
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}
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void extract_(std::string_view str, unsigned int* value) {
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*value = (unsigned int)std::atoi(str.data());
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}
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void extract_(std::string_view str, long* value) {
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*value = std::atol(str.data());
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}
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void extract_(std::string_view str, unsigned long* value) {
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*value = (unsigned long)std::atol(str.data());
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}
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void extract_(std::string_view str, double* value) {
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*value = std::atof(str.data());
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}
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void extract_(std::string_view str, char** value) {
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*value = (char*)str.data();
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}
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void extract_(std::string_view str, string_view* value) {
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*value = str;
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}
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//! Specialization (as overload function) to handle void* types
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void extract_ (const char* str, void* value) noexcept {
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(void)*str; (void)value;
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}
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private:
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std::string_view buffer_;
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std::array<jpair_t, N> pairs_;
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bool valid_;
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};
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#endif /* JSON_H_ */
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