mirror of
https://github.com/nlohmann/json.git
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500 lines
18 KiB
C++
500 lines
18 KiB
C++
#pragma once
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#include <cmath> // isfinite
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#include <cstdint> // uint8_t
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#include <functional> // function
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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/input/input_adapters.hpp>
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#include <nlohmann/detail/input/json_sax.hpp>
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#include <nlohmann/detail/input/lexer.hpp>
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#include <nlohmann/detail/macro_scope.hpp>
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#include <nlohmann/detail/meta/is_sax.hpp>
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#include <nlohmann/detail/value_t.hpp>
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namespace nlohmann
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{
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namespace detail
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{
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////////////
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// parser //
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////////////
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enum class parse_event_t : std::uint8_t
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{
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/// the parser read `{` and started to process a JSON object
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object_start,
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/// the parser read `}` and finished processing a JSON object
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object_end,
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/// the parser read `[` and started to process a JSON array
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array_start,
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/// the parser read `]` and finished processing a JSON array
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array_end,
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/// the parser read a key of a value in an object
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key,
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/// the parser finished reading a JSON value
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value
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};
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template<typename BasicJsonType>
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using parser_callback_t =
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std::function<bool(int /*depth*/, parse_event_t /*event*/, BasicJsonType& /*parsed*/)>;
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/*!
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@brief syntax analysis
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This class implements a recursive descent parser.
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*/
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template<typename BasicJsonType, typename InputAdapterType>
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class parser
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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 lexer_t = lexer<BasicJsonType, InputAdapterType>;
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using token_type = typename lexer_t::token_type;
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public:
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/// a parser reading from an input adapter
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explicit parser(InputAdapterType&& adapter,
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const parser_callback_t<BasicJsonType> cb = nullptr,
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const bool allow_exceptions_ = true,
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const bool skip_comments = false)
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: callback(cb)
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, m_lexer(std::move(adapter), skip_comments)
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, allow_exceptions(allow_exceptions_)
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{
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// read first token
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get_token();
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}
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/*!
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@brief public parser interface
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@param[in] strict whether to expect the last token to be EOF
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@param[in,out] result parsed JSON value
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@throw parse_error.101 in case of an unexpected token
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@throw parse_error.102 if to_unicode fails or surrogate error
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@throw parse_error.103 if to_unicode fails
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*/
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void parse(const bool strict, BasicJsonType& result)
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{
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if (callback)
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{
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json_sax_dom_callback_parser<BasicJsonType> sdp(result, callback, allow_exceptions);
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sax_parse_internal(&sdp);
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// in strict mode, input must be completely read
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if (strict && (get_token() != token_type::end_of_input))
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{
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sdp.parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(),
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exception_message(token_type::end_of_input, "value"), BasicJsonType()));
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}
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// in case of an error, return discarded value
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if (sdp.is_errored())
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{
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result = value_t::discarded;
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return;
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}
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// set top-level value to null if it was discarded by the callback
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// function
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if (result.is_discarded())
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{
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result = nullptr;
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}
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}
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else
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{
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json_sax_dom_parser<BasicJsonType> sdp(result, allow_exceptions);
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sax_parse_internal(&sdp);
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// in strict mode, input must be completely read
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if (strict && (get_token() != token_type::end_of_input))
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{
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sdp.parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), BasicJsonType()));
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}
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// in case of an error, return discarded value
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if (sdp.is_errored())
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{
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result = value_t::discarded;
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return;
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}
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}
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result.assert_invariant();
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}
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/*!
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@brief public accept interface
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@param[in] strict whether to expect the last token to be EOF
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@return whether the input is a proper JSON text
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*/
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bool accept(const bool strict = true)
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{
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json_sax_acceptor<BasicJsonType> sax_acceptor;
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return sax_parse(&sax_acceptor, strict);
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}
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template<typename SAX>
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JSON_HEDLEY_NON_NULL(2)
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bool sax_parse(SAX* sax, const bool strict = true)
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{
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(void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
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const bool result = sax_parse_internal(sax);
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// strict mode: next byte must be EOF
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if (result && strict && (get_token() != token_type::end_of_input))
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{
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), BasicJsonType()));
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}
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return result;
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}
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private:
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template<typename SAX>
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JSON_HEDLEY_NON_NULL(2)
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bool sax_parse_internal(SAX* sax)
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{
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// stack to remember the hierarchy of structured values we are parsing
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// true = array; false = object
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std::vector<bool> states;
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// value to avoid a goto (see comment where set to true)
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bool skip_to_state_evaluation = false;
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while (true)
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{
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if (!skip_to_state_evaluation)
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{
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// invariant: get_token() was called before each iteration
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switch (last_token)
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{
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case token_type::begin_object:
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->start_object(std::size_t(-1))))
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{
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return false;
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}
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// closing } -> we are done
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if (get_token() == token_type::end_object)
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->end_object()))
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{
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return false;
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}
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break;
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}
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// parse key
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if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
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{
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), BasicJsonType()));
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}
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if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
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{
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return false;
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}
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// parse separator (:)
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if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
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{
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), BasicJsonType()));
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}
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// remember we are now inside an object
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states.push_back(false);
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// parse values
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get_token();
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continue;
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}
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case token_type::begin_array:
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->start_array(std::size_t(-1))))
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{
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return false;
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}
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// closing ] -> we are done
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if (get_token() == token_type::end_array)
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->end_array()))
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{
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return false;
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}
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break;
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}
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// remember we are now inside an array
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states.push_back(true);
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// parse values (no need to call get_token)
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continue;
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}
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case token_type::value_float:
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{
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const auto res = m_lexer.get_number_float();
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if (JSON_HEDLEY_UNLIKELY(!std::isfinite(res)))
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{
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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out_of_range::create(406, "number overflow parsing '" + m_lexer.get_token_string() + "'", BasicJsonType()));
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}
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if (JSON_HEDLEY_UNLIKELY(!sax->number_float(res, m_lexer.get_string())))
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{
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return false;
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}
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break;
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}
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case token_type::literal_false:
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->boolean(false)))
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{
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return false;
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}
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break;
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}
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case token_type::literal_null:
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->null()))
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{
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return false;
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}
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break;
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}
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case token_type::literal_true:
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->boolean(true)))
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{
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return false;
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}
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break;
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}
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case token_type::value_integer:
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->number_integer(m_lexer.get_number_integer())))
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{
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return false;
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}
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break;
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}
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case token_type::value_string:
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->string(m_lexer.get_string())))
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{
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return false;
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}
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break;
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}
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case token_type::value_unsigned:
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->number_unsigned(m_lexer.get_number_unsigned())))
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{
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return false;
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}
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break;
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}
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case token_type::parse_error:
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{
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// using "uninitialized" to avoid "expected" message
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::uninitialized, "value"), BasicJsonType()));
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}
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case token_type::uninitialized:
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case token_type::end_array:
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case token_type::end_object:
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case token_type::name_separator:
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case token_type::value_separator:
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case token_type::end_of_input:
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case token_type::literal_or_value:
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default: // the last token was unexpected
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{
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), BasicJsonType()));
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}
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}
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}
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else
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{
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skip_to_state_evaluation = false;
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}
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// we reached this line after we successfully parsed a value
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if (states.empty())
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{
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// empty stack: we reached the end of the hierarchy: done
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return true;
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}
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if (states.back()) // array
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{
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// comma -> next value
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if (get_token() == token_type::value_separator)
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{
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// parse a new value
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get_token();
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continue;
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}
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// closing ]
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if (JSON_HEDLEY_LIKELY(last_token == token_type::end_array))
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->end_array()))
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{
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return false;
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}
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// We are done with this array. Before we can parse a
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// new value, we need to evaluate the new state first.
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// By setting skip_to_state_evaluation to false, we
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// are effectively jumping to the beginning of this if.
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JSON_ASSERT(!states.empty());
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states.pop_back();
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skip_to_state_evaluation = true;
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continue;
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}
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_array, "array"), BasicJsonType()));
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}
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// states.back() is false -> object
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// comma -> next value
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if (get_token() == token_type::value_separator)
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{
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// parse key
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if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::value_string))
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{
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), BasicJsonType()));
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}
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if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
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{
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return false;
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}
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// parse separator (:)
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if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
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{
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), BasicJsonType()));
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}
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// parse values
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get_token();
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continue;
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}
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// closing }
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if (JSON_HEDLEY_LIKELY(last_token == token_type::end_object))
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{
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if (JSON_HEDLEY_UNLIKELY(!sax->end_object()))
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{
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return false;
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}
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// We are done with this object. Before we can parse a
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// new value, we need to evaluate the new state first.
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// By setting skip_to_state_evaluation to false, we
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// are effectively jumping to the beginning of this if.
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JSON_ASSERT(!states.empty());
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states.pop_back();
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skip_to_state_evaluation = true;
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continue;
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}
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return sax->parse_error(m_lexer.get_position(),
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m_lexer.get_token_string(),
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parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_object, "object"), BasicJsonType()));
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}
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}
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/// get next token from lexer
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token_type get_token()
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{
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return last_token = m_lexer.scan();
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}
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std::string exception_message(const token_type expected, const std::string& context)
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{
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std::string error_msg = "syntax error ";
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if (!context.empty())
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{
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error_msg += "while parsing " + context + " ";
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}
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error_msg += "- ";
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if (last_token == token_type::parse_error)
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{
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error_msg += std::string(m_lexer.get_error_message()) + "; last read: '" +
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m_lexer.get_token_string() + "'";
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}
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else
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{
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error_msg += "unexpected " + std::string(lexer_t::token_type_name(last_token));
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}
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if (expected != token_type::uninitialized)
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{
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error_msg += "; expected " + std::string(lexer_t::token_type_name(expected));
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}
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return error_msg;
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}
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private:
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/// callback function
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const parser_callback_t<BasicJsonType> callback = nullptr;
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/// the type of the last read token
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token_type last_token = token_type::uninitialized;
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/// the lexer
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lexer_t m_lexer;
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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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} // namespace detail
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} // namespace nlohmann
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