727 lines
21 KiB
C++
727 lines
21 KiB
C++
#pragma once
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#include <cassert> // assert
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#include <cstddef>
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#include <string> // string
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#include <utility> // move
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#include <vector> // vector
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#include <nlohmann/detail/exceptions.hpp>
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#include <nlohmann/detail/macro_scope.hpp>
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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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This class describes the SAX interface used by @ref nlohmann::json::sax_parse.
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Each function is called in different situations while the input is parsed. The
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boolean return value informs the parser whether to continue processing the
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input.
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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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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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using string_t = typename BasicJsonType::string_t;
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using binary_t = typename BasicJsonType::binary_t;
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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 string_t& 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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@note It is safe to move the passed string.
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*/
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virtual bool string(string_t& val) = 0;
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/*!
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@brief a binary string was read
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@param[in] val binary value
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@return whether parsing should proceed
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@note It is safe to move the passed binary.
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*/
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virtual bool binary(binary_t& 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 -1 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) = 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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@note It is safe to move the passed string.
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*/
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virtual bool key(string_t& 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 -1 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) = 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 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] ex an exception object describing the error
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@return whether parsing should proceed (must return false)
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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 detail::exception& ex) = 0;
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virtual ~json_sax() = default;
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};
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namespace detail
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{
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/*!
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@brief SAX implementation to create a JSON value from SAX events
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This class implements the @ref json_sax interface and processes the SAX events
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to create a JSON value which makes it basically a DOM parser. The structure or
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hierarchy of the JSON value is managed by the stack `ref_stack` which contains
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a pointer to the respective array or object for each recursion depth.
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After successful parsing, the value that is passed by reference to the
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constructor contains the parsed value.
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@tparam BasicJsonType the JSON type
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*/
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template<typename BasicJsonType>
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class json_sax_dom_parser
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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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using string_t = typename BasicJsonType::string_t;
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using binary_t = typename BasicJsonType::binary_t;
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/*!
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@param[in, out] r reference to a JSON value that is manipulated while
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parsing
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@param[in] allow_exceptions_ whether parse errors yield exceptions
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*/
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explicit 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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// make class move-only
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json_sax_dom_parser(const json_sax_dom_parser&) = delete;
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json_sax_dom_parser(json_sax_dom_parser&&) = default;
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json_sax_dom_parser& operator=(const json_sax_dom_parser&) = delete;
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json_sax_dom_parser& operator=(json_sax_dom_parser&&) = default;
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~json_sax_dom_parser() = default;
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bool null()
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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)
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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)
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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)
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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 string_t& /*unused*/)
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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(string_t& val)
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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 binary(binary_t& val)
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{
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handle_value(std::move(val));
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return true;
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}
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bool start_object(std::size_t len)
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{
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ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
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if (JSON_HEDLEY_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
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{
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JSON_THROW(out_of_range::create(408,
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"excessive object size: " + std::to_string(len)));
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}
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return true;
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}
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bool key(string_t& val)
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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()
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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 len)
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{
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ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
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if (JSON_HEDLEY_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
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{
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JSON_THROW(out_of_range::create(408,
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"excessive array size: " + std::to_string(len)));
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}
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return true;
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}
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bool end_array()
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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 parse_error(std::size_t /*unused*/, const std::string& /*unused*/,
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const detail::exception& ex)
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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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// determine the proper exception type from the id
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switch ((ex.id / 100) % 100)
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{
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case 1:
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JSON_THROW(*static_cast<const detail::parse_error*>(&ex));
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case 4:
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JSON_THROW(*static_cast<const detail::out_of_range*>(&ex));
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// LCOV_EXCL_START
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case 2:
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JSON_THROW(*static_cast<const detail::invalid_iterator*>(&ex));
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case 3:
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JSON_THROW(*static_cast<const detail::type_error*>(&ex));
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case 5:
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JSON_THROW(*static_cast<const detail::other_error*>(&ex));
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default:
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assert(false);
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// LCOV_EXCL_STOP
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}
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}
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return false;
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}
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constexpr 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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JSON_HEDLEY_RETURNS_NON_NULL
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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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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->emplace_back(std::forward<Value>(v));
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return &(ref_stack.back()->m_value.array->back());
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}
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assert(ref_stack.back()->is_object());
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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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/// 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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template<typename BasicJsonType>
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class json_sax_dom_callback_parser
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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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using string_t = typename BasicJsonType::string_t;
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using binary_t = typename BasicJsonType::binary_t;
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using parser_callback_t = typename BasicJsonType::parser_callback_t;
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using parse_event_t = typename BasicJsonType::parse_event_t;
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json_sax_dom_callback_parser(BasicJsonType& r,
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const parser_callback_t cb,
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const bool allow_exceptions_ = true)
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: root(r), callback(cb), allow_exceptions(allow_exceptions_)
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{
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keep_stack.push_back(true);
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}
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// make class move-only
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json_sax_dom_callback_parser(const json_sax_dom_callback_parser&) = delete;
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json_sax_dom_callback_parser(json_sax_dom_callback_parser&&) = default;
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json_sax_dom_callback_parser& operator=(const json_sax_dom_callback_parser&) = delete;
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json_sax_dom_callback_parser& operator=(json_sax_dom_callback_parser&&) = default;
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~json_sax_dom_callback_parser() = default;
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bool null()
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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)
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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)
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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)
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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 string_t& /*unused*/)
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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(string_t& val)
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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 binary(binary_t& val)
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{
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handle_value(std::move(val));
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return true;
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}
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bool start_object(std::size_t len)
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{
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// check callback for object start
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const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
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keep_stack.push_back(keep);
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auto val = handle_value(BasicJsonType::value_t::object, true);
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ref_stack.push_back(val.second);
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// check object limit
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if (ref_stack.back() and JSON_HEDLEY_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
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{
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JSON_THROW(out_of_range::create(408, "excessive object size: " + std::to_string(len)));
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}
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return true;
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}
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bool key(string_t& val)
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{
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BasicJsonType k = BasicJsonType(val);
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// check callback for key
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const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::key, k);
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key_keep_stack.push_back(keep);
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// add discarded value at given key and store the reference for later
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if (keep and ref_stack.back())
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{
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object_element = &(ref_stack.back()->m_value.object->operator[](val) = discarded);
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}
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return true;
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}
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bool end_object()
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{
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if (ref_stack.back() and not callback(static_cast<int>(ref_stack.size()) - 1, parse_event_t::object_end, *ref_stack.back()))
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{
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// discard object
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*ref_stack.back() = discarded;
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}
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assert(not ref_stack.empty());
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assert(not keep_stack.empty());
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ref_stack.pop_back();
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keep_stack.pop_back();
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if (not ref_stack.empty() and ref_stack.back() and ref_stack.back()->is_structured())
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{
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// remove discarded value
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for (auto it = ref_stack.back()->begin(); it != ref_stack.back()->end(); ++it)
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{
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if (it->is_discarded())
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{
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ref_stack.back()->erase(it);
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break;
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}
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}
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}
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return true;
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}
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bool start_array(std::size_t len)
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{
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const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
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keep_stack.push_back(keep);
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auto val = handle_value(BasicJsonType::value_t::array, true);
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ref_stack.push_back(val.second);
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// check array limit
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if (ref_stack.back() and JSON_HEDLEY_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
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{
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JSON_THROW(out_of_range::create(408, "excessive array size: " + std::to_string(len)));
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}
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return true;
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}
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bool end_array()
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{
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bool keep = true;
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if (ref_stack.back())
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{
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keep = callback(static_cast<int>(ref_stack.size()) - 1, parse_event_t::array_end, *ref_stack.back());
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if (not keep)
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{
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// discard array
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*ref_stack.back() = discarded;
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}
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}
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assert(not ref_stack.empty());
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assert(not keep_stack.empty());
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ref_stack.pop_back();
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keep_stack.pop_back();
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// remove discarded value
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if (not keep and not ref_stack.empty() and ref_stack.back()->is_array())
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{
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ref_stack.back()->m_value.array->pop_back();
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}
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return true;
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}
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bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/,
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const detail::exception& ex)
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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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// determine the proper exception type from the id
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switch ((ex.id / 100) % 100)
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{
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case 1:
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JSON_THROW(*static_cast<const detail::parse_error*>(&ex));
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case 4:
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JSON_THROW(*static_cast<const detail::out_of_range*>(&ex));
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// LCOV_EXCL_START
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case 2:
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JSON_THROW(*static_cast<const detail::invalid_iterator*>(&ex));
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case 3:
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JSON_THROW(*static_cast<const detail::type_error*>(&ex));
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case 5:
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JSON_THROW(*static_cast<const detail::other_error*>(&ex));
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default:
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assert(false);
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// LCOV_EXCL_STOP
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}
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}
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return false;
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}
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constexpr 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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@param[in] v value to add to the JSON value we build during parsing
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@param[in] skip_callback whether we should skip calling the callback
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function; this is required after start_array() and
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start_object() SAX events, because otherwise we would call the
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callback function with an empty array or object, respectively.
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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
|
|
|
|
@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
|