#pragma once #include <cassert> // assert #include <cstddef> #include <string> // string #include <utility> // move #include <vector> // vector #include <nlohmann/detail/exceptions.hpp> #include <nlohmann/detail/macro_scope.hpp> namespace nlohmann { /*! @brief SAX interface This class describes the SAX interface used by @ref nlohmann::json::sax_parse. Each function is called in different situations while the input is parsed. The boolean return value informs the parser whether to continue processing the input. */ template<typename BasicJsonType> struct json_sax { using number_integer_t = typename BasicJsonType::number_integer_t; using number_unsigned_t = typename BasicJsonType::number_unsigned_t; using number_float_t = typename BasicJsonType::number_float_t; using string_t = typename BasicJsonType::string_t; using binary_t = typename BasicJsonType::binary_t; /*! @brief a null value was read @return whether parsing should proceed */ virtual bool null() = 0; /*! @brief a boolean value was read @param[in] val boolean value @return whether parsing should proceed */ virtual bool boolean(bool val) = 0; /*! @brief an integer number was read @param[in] val integer value @return whether parsing should proceed */ virtual bool number_integer(number_integer_t val) = 0; /*! @brief an unsigned integer number was read @param[in] val unsigned integer value @return whether parsing should proceed */ virtual bool number_unsigned(number_unsigned_t val) = 0; /*! @brief an floating-point number was read @param[in] val floating-point value @param[in] s raw token value @return whether parsing should proceed */ virtual bool number_float(number_float_t val, const string_t& s) = 0; /*! @brief a string was read @param[in] val string value @return whether parsing should proceed @note It is safe to move the passed string. */ virtual bool string(string_t& val) = 0; /*! @brief a binary string was read @param[in] val binary value @return whether parsing should proceed @note It is safe to move the passed binary. */ virtual bool binary(binary_t& val) = 0; /*! @brief the beginning of an object was read @param[in] elements number of object elements or -1 if unknown @return whether parsing should proceed @note binary formats may report the number of elements */ virtual bool start_object(std::size_t elements) = 0; /*! @brief an object key was read @param[in] val object key @return whether parsing should proceed @note It is safe to move the passed string. */ virtual bool key(string_t& val) = 0; /*! @brief the end of an object was read @return whether parsing should proceed */ virtual bool end_object() = 0; /*! @brief the beginning of an array was read @param[in] elements number of array elements or -1 if unknown @return whether parsing should proceed @note binary formats may report the number of elements */ virtual bool start_array(std::size_t elements) = 0; /*! @brief the end of an array was read @return whether parsing should proceed */ virtual bool end_array() = 0; /*! @brief a parse error occurred @param[in] position the position in the input where the error occurs @param[in] last_token the last read token @param[in] ex an exception object describing the error @return whether parsing should proceed (must return false) */ virtual bool parse_error(std::size_t position, const std::string& last_token, const detail::exception& ex) = 0; virtual ~json_sax() = default; }; namespace detail { /*! @brief SAX implementation to create a JSON value from SAX events This class implements the @ref json_sax interface and processes the SAX events to create a JSON value which makes it basically a DOM parser. The structure or hierarchy of the JSON value is managed by the stack `ref_stack` which contains a pointer to the respective array or object for each recursion depth. After successful parsing, the value that is passed by reference to the constructor contains the parsed value. @tparam BasicJsonType the JSON type */ template<typename BasicJsonType> class json_sax_dom_parser { public: using number_integer_t = typename BasicJsonType::number_integer_t; using number_unsigned_t = typename BasicJsonType::number_unsigned_t; using number_float_t = typename BasicJsonType::number_float_t; using string_t = typename BasicJsonType::string_t; using binary_t = typename BasicJsonType::binary_t; /*! @param[in, out] r reference to a JSON value that is manipulated while parsing @param[in] allow_exceptions_ whether parse errors yield exceptions */ explicit json_sax_dom_parser(BasicJsonType& r, const bool allow_exceptions_ = true) : root(r), allow_exceptions(allow_exceptions_) {} // make class move-only json_sax_dom_parser(const json_sax_dom_parser&) = delete; json_sax_dom_parser(json_sax_dom_parser&&) = default; json_sax_dom_parser& operator=(const json_sax_dom_parser&) = delete; json_sax_dom_parser& operator=(json_sax_dom_parser&&) = default; ~json_sax_dom_parser() = default; bool null() { handle_value(nullptr); return true; } bool boolean(bool val) { handle_value(val); return true; } bool number_integer(number_integer_t val) { handle_value(val); return true; } bool number_unsigned(number_unsigned_t val) { handle_value(val); return true; } bool number_float(number_float_t val, const string_t& /*unused*/) { handle_value(val); return true; } bool string(string_t& val) { handle_value(val); return true; } bool binary(binary_t& val) { handle_value(std::move(val)); return true; } bool start_object(std::size_t len) { ref_stack.push_back(handle_value(BasicJsonType::value_t::object)); if (JSON_HEDLEY_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size())) { JSON_THROW(out_of_range::create(408, "excessive object size: " + std::to_string(len))); } return true; } bool key(string_t& val) { // add null at given key and store the reference for later object_element = &(ref_stack.back()->m_value.object->operator[](val)); return true; } bool end_object() { ref_stack.pop_back(); return true; } bool start_array(std::size_t len) { ref_stack.push_back(handle_value(BasicJsonType::value_t::array)); if (JSON_HEDLEY_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size())) { JSON_THROW(out_of_range::create(408, "excessive array size: " + std::to_string(len))); } return true; } bool end_array() { ref_stack.pop_back(); return true; } bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const detail::exception& ex) { errored = true; if (allow_exceptions) { // determine the proper exception type from the id switch ((ex.id / 100) % 100) { case 1: JSON_THROW(*static_cast<const detail::parse_error*>(&ex)); case 4: JSON_THROW(*static_cast<const detail::out_of_range*>(&ex)); // LCOV_EXCL_START case 2: JSON_THROW(*static_cast<const detail::invalid_iterator*>(&ex)); case 3: JSON_THROW(*static_cast<const detail::type_error*>(&ex)); case 5: JSON_THROW(*static_cast<const detail::other_error*>(&ex)); default: assert(false); // LCOV_EXCL_STOP } } return false; } constexpr bool is_errored() const { return errored; } private: /*! @invariant If the ref stack is empty, then the passed value will be the new root. @invariant If the ref stack contains a value, then it is an array or an object to which we can add elements */ template<typename Value> JSON_HEDLEY_RETURNS_NON_NULL BasicJsonType* handle_value(Value&& v) { if (ref_stack.empty()) { root = BasicJsonType(std::forward<Value>(v)); return &root; } assert(ref_stack.back()->is_array() or ref_stack.back()->is_object()); if (ref_stack.back()->is_array()) { ref_stack.back()->m_value.array->emplace_back(std::forward<Value>(v)); return &(ref_stack.back()->m_value.array->back()); } assert(ref_stack.back()->is_object()); assert(object_element); *object_element = BasicJsonType(std::forward<Value>(v)); return object_element; } /// the parsed JSON value BasicJsonType& root; /// stack to model hierarchy of values std::vector<BasicJsonType*> ref_stack {}; /// helper to hold the reference for the next object element BasicJsonType* object_element = nullptr; /// whether a syntax error occurred bool errored = false; /// whether to throw exceptions in case of errors const bool allow_exceptions = true; }; template<typename BasicJsonType> class json_sax_dom_callback_parser { public: using number_integer_t = typename BasicJsonType::number_integer_t; using number_unsigned_t = typename BasicJsonType::number_unsigned_t; using number_float_t = typename BasicJsonType::number_float_t; using string_t = typename BasicJsonType::string_t; using binary_t = typename BasicJsonType::binary_t; using parser_callback_t = typename BasicJsonType::parser_callback_t; using parse_event_t = typename BasicJsonType::parse_event_t; json_sax_dom_callback_parser(BasicJsonType& r, const parser_callback_t cb, const bool allow_exceptions_ = true) : root(r), callback(cb), allow_exceptions(allow_exceptions_) { keep_stack.push_back(true); } // make class move-only json_sax_dom_callback_parser(const json_sax_dom_callback_parser&) = delete; json_sax_dom_callback_parser(json_sax_dom_callback_parser&&) = default; json_sax_dom_callback_parser& operator=(const json_sax_dom_callback_parser&) = delete; json_sax_dom_callback_parser& operator=(json_sax_dom_callback_parser&&) = default; ~json_sax_dom_callback_parser() = default; bool null() { handle_value(nullptr); return true; } bool boolean(bool val) { handle_value(val); return true; } bool number_integer(number_integer_t val) { handle_value(val); return true; } bool number_unsigned(number_unsigned_t val) { handle_value(val); return true; } bool number_float(number_float_t val, const string_t& /*unused*/) { handle_value(val); return true; } bool string(string_t& val) { handle_value(val); return true; } bool binary(binary_t& val) { handle_value(std::move(val)); return true; } bool start_object(std::size_t len) { // check callback for object start const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded); keep_stack.push_back(keep); auto val = handle_value(BasicJsonType::value_t::object, true); ref_stack.push_back(val.second); // check object limit if (ref_stack.back() and JSON_HEDLEY_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size())) { JSON_THROW(out_of_range::create(408, "excessive object size: " + std::to_string(len))); } return true; } bool key(string_t& val) { BasicJsonType k = BasicJsonType(val); // check callback for key const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::key, k); key_keep_stack.push_back(keep); // add discarded value at given key and store the reference for later if (keep and ref_stack.back()) { object_element = &(ref_stack.back()->m_value.object->operator[](val) = discarded); } return true; } bool end_object() { if (ref_stack.back() and not callback(static_cast<int>(ref_stack.size()) - 1, parse_event_t::object_end, *ref_stack.back())) { // discard object *ref_stack.back() = discarded; } assert(not ref_stack.empty()); assert(not keep_stack.empty()); ref_stack.pop_back(); keep_stack.pop_back(); if (not ref_stack.empty() and ref_stack.back() and ref_stack.back()->is_object()) { // remove discarded value for (auto it = ref_stack.back()->begin(); it != ref_stack.back()->end(); ++it) { if (it->is_discarded()) { ref_stack.back()->erase(it); break; } } } return true; } bool start_array(std::size_t len) { const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded); keep_stack.push_back(keep); auto val = handle_value(BasicJsonType::value_t::array, true); ref_stack.push_back(val.second); // check array limit if (ref_stack.back() and JSON_HEDLEY_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size())) { JSON_THROW(out_of_range::create(408, "excessive array size: " + std::to_string(len))); } return true; } bool end_array() { bool keep = true; if (ref_stack.back()) { keep = callback(static_cast<int>(ref_stack.size()) - 1, parse_event_t::array_end, *ref_stack.back()); if (not keep) { // discard array *ref_stack.back() = discarded; } } assert(not ref_stack.empty()); assert(not keep_stack.empty()); ref_stack.pop_back(); keep_stack.pop_back(); // remove discarded value if (not keep and not ref_stack.empty() and ref_stack.back()->is_array()) { ref_stack.back()->m_value.array->pop_back(); } return true; } bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const detail::exception& ex) { errored = true; if (allow_exceptions) { // determine the proper exception type from the id switch ((ex.id / 100) % 100) { case 1: JSON_THROW(*static_cast<const detail::parse_error*>(&ex)); case 4: JSON_THROW(*static_cast<const detail::out_of_range*>(&ex)); // LCOV_EXCL_START case 2: JSON_THROW(*static_cast<const detail::invalid_iterator*>(&ex)); case 3: JSON_THROW(*static_cast<const detail::type_error*>(&ex)); case 5: JSON_THROW(*static_cast<const detail::other_error*>(&ex)); default: assert(false); // LCOV_EXCL_STOP } } return false; } constexpr bool is_errored() const { return errored; } private: /*! @param[in] v value to add to the JSON value we build during parsing @param[in] skip_callback whether we should skip calling the callback function; this is required after start_array() and start_object() SAX events, because otherwise we would call the callback function with an empty array or object, respectively. @invariant If the ref stack is empty, then the passed value will be the new root. @invariant If the ref stack contains a value, then it is an array or an object to which we can add elements @return pair of boolean (whether value should be kept) and pointer (to the passed value in the ref_stack hierarchy; nullptr if not kept) */ template<typename Value> std::pair<bool, BasicJsonType*> handle_value(Value&& v, const bool skip_callback = false) { assert(not keep_stack.empty()); // do not handle this value if we know it would be added to a discarded // container if (not keep_stack.back()) { return {false, nullptr}; } // create value auto value = BasicJsonType(std::forward<Value>(v)); // check callback const bool keep = skip_callback or callback(static_cast<int>(ref_stack.size()), parse_event_t::value, value); // do not handle this value if we just learnt it shall be discarded if (not keep) { return {false, nullptr}; } if (ref_stack.empty()) { root = std::move(value); return {true, &root}; } // skip this value if we already decided to skip the parent // (https://github.com/nlohmann/json/issues/971#issuecomment-413678360) if (not ref_stack.back()) { return {false, nullptr}; } // we now only expect arrays and objects assert(ref_stack.back()->is_array() or ref_stack.back()->is_object()); // array if (ref_stack.back()->is_array()) { ref_stack.back()->m_value.array->push_back(std::move(value)); return {true, &(ref_stack.back()->m_value.array->back())}; } // object assert(ref_stack.back()->is_object()); // check if we should store an element for the current key assert(not key_keep_stack.empty()); const bool store_element = key_keep_stack.back(); key_keep_stack.pop_back(); if (not store_element) { return {false, nullptr}; } assert(object_element); *object_element = std::move(value); return {true, object_element}; } /// the parsed JSON value BasicJsonType& root; /// stack to model hierarchy of values std::vector<BasicJsonType*> ref_stack {}; /// stack to manage which values to keep std::vector<bool> keep_stack {}; /// stack to manage which object keys to keep std::vector<bool> key_keep_stack {}; /// helper to hold the reference for the next object element BasicJsonType* object_element = nullptr; /// whether a syntax error occurred bool errored = false; /// callback function const parser_callback_t callback = nullptr; /// whether to throw exceptions in case of errors const bool allow_exceptions = true; /// a discarded value for the callback BasicJsonType discarded = BasicJsonType::value_t::discarded; }; template<typename BasicJsonType> class json_sax_acceptor { public: using number_integer_t = typename BasicJsonType::number_integer_t; using number_unsigned_t = typename BasicJsonType::number_unsigned_t; using number_float_t = typename BasicJsonType::number_float_t; using string_t = typename BasicJsonType::string_t; using binary_t = typename BasicJsonType::binary_t; bool null() { return true; } bool boolean(bool /*unused*/) { return true; } bool number_integer(number_integer_t /*unused*/) { return true; } bool number_unsigned(number_unsigned_t /*unused*/) { return true; } bool number_float(number_float_t /*unused*/, const string_t& /*unused*/) { return true; } bool string(string_t& /*unused*/) { return true; } bool binary(binary_t& /*unused*/) { return true; } bool start_object(std::size_t /*unused*/ = std::size_t(-1)) { return true; } bool key(string_t& /*unused*/) { return true; } bool end_object() { return true; } bool start_array(std::size_t /*unused*/ = std::size_t(-1)) { return true; } bool end_array() { return true; } bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const detail::exception& /*unused*/) { return false; } }; } // namespace detail } // namespace nlohmann