mirror of
https://github.com/nlohmann/json.git
synced 2026-10-06 22:47:13 +00:00
Niels Lohmann
0adb7783a4
Give basic_json_view the read-only access functions of basic_json: operator[] and at() with keys and indices, front()/back(), find(), contains(), count(), begin()/end() and cbegin()/cend(), items() with structured bindings from C++17 on, and type_name(). Exceptions have the ids and messages of the const functions of basic_json. Where basic_json has undefined behavior the view answers safely: operator[] with a missing key or an out-of-range index returns a discarded view, and front()/back() of an empty container throw invalid_iterator.214. Objects are iterated in document order, and all members are visited; duplicate-key lookups find the first member (as yyjson and simdjson do), while parse(), materialize(), and the map conversions keep the last value, as parse() does. Keys of up to 16 bytes are compared with two overlapping loads. Add value conversions: get<T>()/get_to() for arithmetic types, bool, nullptr_t, strings (std::basic_string copied, string_view_t without a copy), BasicJsonType, views, std::vector, and maps with string keys; get_string() for the string without a copy; number_token() for the number exactly as written in the source; value() with keys and JSON pointers; and operator[]/at()/ contains() with JSON pointers. Everything else, including types with from_json(), goes through materialize() of that subtree. get<T>() of arithmetic types is inlined down to the conversion, so reading an integer needs no call. detail::json_pointer_access exposes a pointer's reference tokens to code outside basic_json. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
92 lines
3.1 KiB
C++
92 lines
3.1 KiB
C++
// __ _____ _____ _____
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// __| | __| | | | JSON for Modern C++
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// | | |__ | | | | | | version 3.12.0
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// |_____|_____|_____|_|___| https://github.com/nlohmann/json
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//
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// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
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// SPDX-License-Identifier: MIT
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#pragma once
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#include <algorithm> // min
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#include <cstddef> // size_t
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#include <string> // string
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#include <nlohmann/json.hpp>
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#include <nlohmann/detail/view/builder.hpp>
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#include <nlohmann/detail/view/macro_scope.hpp>
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NLOHMANN_JSON_NAMESPACE_BEGIN
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namespace detail
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{
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namespace view
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{
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// Exceptions are thrown out of line, so that the accessors that may throw stay
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// small enough to be inlined.
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[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(int id, const char* prefix, const char* type)
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{
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NLOHMANN_VIEW_THROW(type_error::create(id, concat(prefix, type), nullptr));
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}
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[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_out_of_range(int id, const std::string& msg)
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{
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NLOHMANN_VIEW_THROW(out_of_range::create(id, msg, nullptr));
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}
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[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_invalid_iterator(int id, const char* msg)
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{
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NLOHMANN_VIEW_THROW(invalid_iterator::create(id, msg, nullptr));
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}
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/// a parse error without a position (as those of json_pointer)
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[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_parse_error(int id, const std::string& msg)
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{
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NLOHMANN_VIEW_THROW(parse_error::create(id, 0, msg, nullptr));
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}
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/*!
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@brief throw the exception BasicJsonType::parse would throw for this input
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The view accepts exactly the inputs parse() accepts, so on a failure the
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library parser is run on the same bytes: it throws the exception parse() would
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throw, with the same message, position, and "last read" token. The error path
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is cold, so this costs nothing on valid input. Should parse() accept the input
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nevertheless (a bug), the view's own failure is reported.
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*/
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template<typename BasicJsonType>
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[[noreturn]] NLOHMANN_VIEW_NOINLINE void throw_parse_failure(const parse_failure& f, const char* src, std::size_t size,
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bool ignore_comments, bool ignore_trailing_commas)
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{
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if (f.code == error_code::input_too_large)
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{
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// LCOV_EXCL_START (4 GiB)
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NLOHMANN_VIEW_THROW(out_of_range::create(416, "input of 4 GiB or more is not supported by json_document", nullptr));
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// LCOV_EXCL_STOP
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}
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const BasicJsonType accepted = BasicJsonType::parse(src, src + size, nullptr, true, ignore_comments, ignore_trailing_commas);
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// LCOV_EXCL_START (only if parse() accepts what the view rejects: a bug)
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static_cast<void>(accepted);
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position_t pos;
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const std::size_t off = (std::min)(f.offset, size);
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pos.chars_read_total = off + 1;
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std::size_t line_start = 0;
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for (std::size_t i = 0; i < off; ++i)
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{
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if (src[i] == '\n')
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{
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++pos.lines_read;
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line_start = i + 1;
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}
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}
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pos.chars_read_current_line = off + 1 - line_start;
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NLOHMANN_VIEW_THROW(parse_error::create(101, pos, "syntax error while parsing value", nullptr));
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// LCOV_EXCL_STOP
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}
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} // namespace view
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} // namespace detail
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NLOHMANN_JSON_NAMESPACE_END
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