681 lines
21 KiB
C++
681 lines
21 KiB
C++
#pragma once
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#include <cassert> // assert
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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 <nlohmann/detail/exceptions.hpp>
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#include <nlohmann/detail/macro_scope.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/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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/*!
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@brief syntax analysis
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This class implements a recursive decent parser.
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*/
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template<typename BasicJsonType>
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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 lexer_t = lexer<BasicJsonType>;
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using token_type = typename lexer_t::token_type;
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public:
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enum class parse_event_t : 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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using json_sax_t = json_sax<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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/// a parser reading from an input adapter
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explicit parser(detail::input_adapter_t adapter,
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const parser_callback_t cb = nullptr,
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const bool allow_exceptions_ = true)
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: callback(cb), m_lexer(adapter), 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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parse_internal(true, result);
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result.assert_invariant();
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// in strict mode, input must be completely read
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if (strict)
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{
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get_token();
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expect(token_type::end_of_input);
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}
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// in case of an error, return discarded value
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if (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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result.assert_invariant();
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// in strict mode, input must be completely read
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if (strict and (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)));
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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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}
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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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if (not sax_parse_internal(&sax_acceptor))
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{
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return false;
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}
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// strict => last token must be EOF
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return not strict or (get_token() == token_type::end_of_input);
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}
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bool sax_parse(json_sax_t* sax)
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{
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return sax_parse_internal(sax);
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}
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private:
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/*!
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@brief the actual parser
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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_internal(bool keep, BasicJsonType& result)
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{
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// never parse after a parse error was detected
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assert(not errored);
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// this function is only called when a callback is given
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assert(callback);
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// start with a discarded value
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if (not result.is_discarded())
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{
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result.m_value.destroy(result.m_type);
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result.m_type = value_t::discarded;
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}
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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 (keep)
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{
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keep = callback(depth++, parse_event_t::object_start, result);
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if (keep)
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{
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// explicitly set result to object to cope with {}
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result.m_type = value_t::object;
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result.m_value = value_t::object;
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}
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}
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// read next token
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get_token();
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// closing } -> we are done
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if (last_token == token_type::end_object)
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{
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if (keep and not callback(--depth, parse_event_t::object_end, result))
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{
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result.m_value.destroy(result.m_type);
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result.m_type = value_t::discarded;
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}
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break;
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}
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// parse values
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std::string key;
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BasicJsonType value;
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while (true)
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{
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// store key
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if (not expect(token_type::value_string))
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{
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return;
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}
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key = m_lexer.move_string();
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bool keep_tag = false;
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if (keep)
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{
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BasicJsonType k(key);
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keep_tag = callback(depth, parse_event_t::key, k);
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}
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// parse separator (:)
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get_token();
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if (not expect(token_type::name_separator))
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{
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return;
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}
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// parse and add value
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get_token();
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value.m_value.destroy(value.m_type);
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value.m_type = value_t::discarded;
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parse_internal(keep, value);
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if (JSON_UNLIKELY(errored))
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{
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return;
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}
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if (keep and keep_tag and not value.is_discarded())
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{
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result.m_value.object->emplace(std::move(key), std::move(value));
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}
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// comma -> next value
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get_token();
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if (last_token == token_type::value_separator)
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{
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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 (not expect(token_type::end_object))
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{
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return;
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}
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break;
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}
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if (keep and not callback(--depth, parse_event_t::object_end, result))
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{
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result.m_value.destroy(result.m_type);
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result.m_type = value_t::discarded;
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}
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break;
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}
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case token_type::begin_array:
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{
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if (keep)
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{
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keep = callback(depth++, parse_event_t::array_start, result);
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if (keep)
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{
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// explicitly set result to array to cope with []
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result.m_type = value_t::array;
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result.m_value = value_t::array;
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}
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}
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// read next token
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get_token();
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// closing ] -> we are done
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if (last_token == token_type::end_array)
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{
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if (not callback(--depth, parse_event_t::array_end, result))
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{
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result.m_value.destroy(result.m_type);
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result.m_type = value_t::discarded;
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}
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break;
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}
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// parse values
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BasicJsonType value;
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while (true)
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{
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// parse value
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value.m_value.destroy(value.m_type);
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value.m_type = value_t::discarded;
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parse_internal(keep, value);
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if (JSON_UNLIKELY(errored))
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{
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return;
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}
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if (keep and not value.is_discarded())
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{
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result.m_value.array->push_back(std::move(value));
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}
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// comma -> next value
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get_token();
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if (last_token == token_type::value_separator)
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{
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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 (not expect(token_type::end_array))
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{
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return;
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}
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break;
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}
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if (keep and not callback(--depth, parse_event_t::array_end, result))
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{
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result.m_value.destroy(result.m_type);
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result.m_type = value_t::discarded;
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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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result.m_type = value_t::null;
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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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result.m_type = value_t::string;
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result.m_value = m_lexer.move_string();
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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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result.m_type = value_t::boolean;
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result.m_value = true;
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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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result.m_type = value_t::boolean;
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result.m_value = false;
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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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result.m_type = value_t::number_unsigned;
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result.m_value = m_lexer.get_number_unsigned();
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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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result.m_type = value_t::number_integer;
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result.m_value = m_lexer.get_number_integer();
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break;
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}
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case token_type::value_float:
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{
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result.m_type = value_t::number_float;
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result.m_value = m_lexer.get_number_float();
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// throw in case of infinity or NAN
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if (JSON_UNLIKELY(not std::isfinite(result.m_value.number_float)))
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{
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if (allow_exceptions)
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{
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JSON_THROW(out_of_range::create(406, "number overflow parsing '" +
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m_lexer.get_token_string() + "'"));
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}
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expect(token_type::uninitialized);
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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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if (not expect(token_type::uninitialized))
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{
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return;
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}
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break; // LCOV_EXCL_LINE
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}
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default:
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{
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// the last token was unexpected; we expected a value
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if (not expect(token_type::literal_or_value))
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{
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return;
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}
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break; // LCOV_EXCL_LINE
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}
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}
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if (keep and not callback(depth, parse_event_t::value, result))
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{
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result.m_value.destroy(result.m_type);
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result.m_type = value_t::discarded;
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}
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}
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bool sax_parse_internal(json_sax_t* sax)
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{
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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 (not sax->start_object())
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{
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return false;
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}
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// read next token
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get_token();
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// closing } -> we are done
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if (JSON_UNLIKELY(last_token == token_type::end_object))
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{
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return sax->end_object();
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}
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// parse values
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while (true)
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{
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// parse key
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if (JSON_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)));
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}
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else
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{
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if (not sax->key(m_lexer.move_string()))
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{
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return false;
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}
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}
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// parse separator (:)
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get_token();
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if (JSON_UNLIKELY(last_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)));
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}
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// parse value
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get_token();
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if (not sax_parse_internal(sax))
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{
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return false;
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}
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// comma -> next value
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get_token();
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if (last_token == token_type::value_separator)
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{
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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_LIKELY(last_token == token_type::end_object))
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{
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return sax->end_object();
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}
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else
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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)));
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}
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}
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}
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case token_type::begin_array:
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{
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if (not sax->start_array())
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{
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return false;
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}
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// read next token
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get_token();
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// closing ] -> we are done
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if (last_token == token_type::end_array)
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{
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return sax->end_array();
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}
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// parse values
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while (true)
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{
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// parse value
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if (not sax_parse_internal(sax))
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{
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return false;
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}
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// comma -> next value
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get_token();
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if (last_token == token_type::value_separator)
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{
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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_LIKELY(last_token == token_type::end_array))
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{
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return sax->end_array();
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}
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else
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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)));
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}
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}
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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_UNLIKELY(not 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() + "'"));
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}
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else
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{
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return sax->number_float(res, m_lexer.move_string());
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}
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}
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case token_type::literal_false:
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{
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return sax->boolean(false);
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}
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case token_type::literal_null:
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{
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return sax->null();
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}
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case token_type::literal_true:
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{
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return sax->boolean(true);
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}
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case token_type::value_integer:
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{
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return sax->number_integer(m_lexer.get_number_integer());
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}
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case token_type::value_string:
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{
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return sax->string(m_lexer.move_string());
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}
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case token_type::value_unsigned:
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{
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return sax->number_unsigned(m_lexer.get_number_unsigned());
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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)));
|
|
}
|
|
|
|
default: // the last token was unexpected
|
|
{
|
|
return sax->parse_error(m_lexer.get_position(),
|
|
m_lexer.get_token_string(),
|
|
parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value)));
|
|
}
|
|
}
|
|
}
|
|
|
|
/// get next token from lexer
|
|
token_type get_token()
|
|
{
|
|
return (last_token = m_lexer.scan());
|
|
}
|
|
|
|
/*!
|
|
@throw parse_error.101 if expected token did not occur
|
|
*/
|
|
bool expect(token_type t)
|
|
{
|
|
if (JSON_UNLIKELY(t != last_token))
|
|
{
|
|
errored = true;
|
|
if (allow_exceptions)
|
|
{
|
|
JSON_THROW(parse_error::create(101, m_lexer.get_position(), exception_message(t)));
|
|
}
|
|
else
|
|
{
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
std::string exception_message(const token_type expected)
|
|
{
|
|
std::string error_msg = "syntax error - ";
|
|
if (last_token == token_type::parse_error)
|
|
{
|
|
error_msg += std::string(m_lexer.get_error_message()) + "; last read: '" +
|
|
m_lexer.get_token_string() + "'";
|
|
}
|
|
else
|
|
{
|
|
error_msg += "unexpected " + std::string(lexer_t::token_type_name(last_token));
|
|
}
|
|
|
|
if (expected != token_type::uninitialized)
|
|
{
|
|
error_msg += "; expected " + std::string(lexer_t::token_type_name(expected));
|
|
}
|
|
|
|
return error_msg;
|
|
}
|
|
|
|
private:
|
|
/// current level of recursion
|
|
int depth = 0;
|
|
/// callback function
|
|
const parser_callback_t callback = nullptr;
|
|
/// the type of the last read token
|
|
token_type last_token = token_type::uninitialized;
|
|
/// the lexer
|
|
lexer_t m_lexer;
|
|
/// whether a syntax error occurred
|
|
bool errored = false;
|
|
/// whether to throw exceptions in case of errors
|
|
const bool allow_exceptions = true;
|
|
};
|
|
}
|
|
}
|