280 lines
7.4 KiB
C++
280 lines
7.4 KiB
C++
#pragma once
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#include <cstddef>
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#include <string>
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#include <vector>
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namespace nlohmann
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{
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/*!
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@brief SAX interface
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*/
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template<typename BasicJsonType>
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struct json_sax
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{
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/// type for (signed) integers
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using number_integer_t = typename BasicJsonType::number_integer_t;
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/// type for unsigned integers
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using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
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/// type for floating-point numbers
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using number_float_t = typename BasicJsonType::number_float_t;
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/// constant to indicate that no size limit is given for array or object
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static constexpr auto no_limit = std::size_t(-1);
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/*!
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@brief a null value was read
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@return whether parsing should proceed
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*/
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virtual bool null() = 0;
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/*!
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@brief a boolean value was read
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@param[in] val boolean value
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@return whether parsing should proceed
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*/
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virtual bool boolean(bool val) = 0;
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/*!
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@brief an integer number was read
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@param[in] val integer value
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@return whether parsing should proceed
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*/
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virtual bool number_integer(number_integer_t val) = 0;
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/*!
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@brief an unsigned integer number was read
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@param[in] val unsigned integer value
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@return whether parsing should proceed
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*/
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virtual bool number_unsigned(number_unsigned_t val) = 0;
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/*!
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@brief an floating-point number was read
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@param[in] val floating-point value
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@param[in] s raw token value
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@return whether parsing should proceed
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*/
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virtual bool number_float(number_float_t val, const std::string& s) = 0;
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/*!
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@brief a string was read
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@param[in] val string value
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@return whether parsing should proceed
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*/
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virtual bool string(std::string&& val) = 0;
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/*!
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@brief the beginning of an object was read
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@param[in] elements number of object elements or no_limit if unknown
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@return whether parsing should proceed
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@note binary formats may report the number of elements
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*/
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virtual bool start_object(std::size_t elements = no_limit) = 0;
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/*!
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@brief an object key was read
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@param[in] val object key
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@return whether parsing should proceed
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*/
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virtual bool key(std::string&& val) = 0;
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/*!
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@brief the end of an object was read
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@return whether parsing should proceed
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*/
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virtual bool end_object() = 0;
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/*!
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@brief the beginning of an array was read
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@param[in] elements number of array elements or no_limit if unknown
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@return whether parsing should proceed
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@note binary formats may report the number of elements
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*/
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virtual bool start_array(std::size_t elements = no_limit) = 0;
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/*!
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@brief the end of an array was read
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@return whether parsing should proceed
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*/
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virtual bool end_array() = 0;
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/*!
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@brief a binary value was read
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@param[in] val byte vector
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@return whether parsing should proceed
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@note examples are CBOR type 2 strings, MessagePack bin, and maybe UBJSON
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array<uint8t>
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*/
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virtual bool binary(const std::vector<uint8_t>& val) = 0;
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/*!
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@brief a parse error occurred
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@param[in] position the position in the input where the error occurs
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@param[in] last_token the last read token
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@param[in] error_msg a detailed error message
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@return whether parsing should proceed
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*/
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virtual bool parse_error(std::size_t position,
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const std::string& last_token,
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const std::string& error_msg) = 0;
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virtual ~json_sax() = default;
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};
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template<typename BasicJsonType>
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class json_sax_dom_parser : public json_sax<BasicJsonType>
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{
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public:
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using number_integer_t = typename BasicJsonType::number_integer_t;
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using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
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using number_float_t = typename BasicJsonType::number_float_t;
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json_sax_dom_parser(BasicJsonType& r, const bool allow_exceptions_ = true)
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: root(r), allow_exceptions(allow_exceptions_)
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{}
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bool null() override
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{
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handle_value(nullptr);
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return true;
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}
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bool boolean(bool val) override
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{
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handle_value(val);
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return true;
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}
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bool number_integer(number_integer_t val) override
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{
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handle_value(val);
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return true;
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}
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bool number_unsigned(number_unsigned_t val) override
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{
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handle_value(val);
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return true;
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}
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bool number_float(number_float_t val, const std::string&) override
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{
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handle_value(val);
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return true;
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}
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bool string(std::string&& val) override
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{
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handle_value(val);
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return true;
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}
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bool start_object(std::size_t) override
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{
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ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
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return true;
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}
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bool key(std::string&& val) override
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{
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// add null at given key and store the reference for later
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object_element = &(ref_stack.back()->m_value.object->operator[](val));
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return true;
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}
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bool end_object() override
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{
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ref_stack.pop_back();
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return true;
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}
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bool start_array(std::size_t) override
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{
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ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
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return true;
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}
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bool end_array() override
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{
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ref_stack.pop_back();
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return true;
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}
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bool binary(const std::vector<uint8_t>&) override
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{
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return true;
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}
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bool parse_error(std::size_t position, const std::string& token,
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const std::string& error_msg) override
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{
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errored = true;
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if (allow_exceptions)
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{
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if (error_msg == "number overflow")
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{
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JSON_THROW(BasicJsonType::out_of_range::create(406, "number overflow parsing '" + token + "'"));
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}
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else
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{
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JSON_THROW(BasicJsonType::parse_error::create(101, position, error_msg));
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}
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}
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return false;
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}
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bool is_errored() const
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{
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return errored;
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}
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private:
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/*!
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@invariant If the ref stack is empty, then the passed value will be the new
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root.
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@invariant If the ref stack contains a value, then it is an array or an
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object to which we can add elements
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*/
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template<typename Value>
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BasicJsonType* handle_value(Value&& v)
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{
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if (ref_stack.empty())
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{
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root = BasicJsonType(std::forward<Value>(v));
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return &root;
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}
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else
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{
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assert(ref_stack.back()->is_array() or ref_stack.back()->is_object());
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if (ref_stack.back()->is_array())
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{
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ref_stack.back()->m_value.array->push_back(BasicJsonType(std::forward<Value>(v)));
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return &(ref_stack.back()->m_value.array->back());
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}
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else
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{
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assert(object_element);
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*object_element = BasicJsonType(std::forward<Value>(v));
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return object_element;
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}
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}
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}
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/// the parsed JSON value
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BasicJsonType& root;
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/// stack to model hierarchy of values
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std::vector<BasicJsonType*> ref_stack;
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/// helper to hold the reference for the next object element
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BasicJsonType* object_element = nullptr;
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/// whether a syntax error occurred
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bool errored = false;
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/// whether to throw exceptions in case of errors
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const bool allow_exceptions = true;
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};
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}
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