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https://github.com/nlohmann/json.git
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Niels Lohmann
4303ba674d
Add json_document and json_view, a read-only, zero-copy index of a JSON text, as the first public slice of the zero-copy view (#5295). A parse produces a flat array of 16-byte nodes in document order, one per value and one per object key. Strings stay in the source text; escaped strings are decoded into an arena. Integers are converted while their digits are in the cache; floats keep only their digit layout and are converted on read. Containers store the size of their subtree, so a reader can step over one in constant time. A document makes a handful of allocations, however many values it has. The parser accepts exactly what json::parse accepts, with every combination of ignore_comments and ignore_trailing_commas, with and without a trailing NUL, and under JSON_STRICT_NUL_HANDLING. It is portable C++11 and does not depend on byte order. basic_json_document adds parse, parse_copy, accept, read (reuses a document's memory), root, is_discarded, source, owns_source, node_count, memory_usage, and shrink_to_fit. basic_json_view adds type, the is_* queries, operator bool, size, empty, materialize, and source_offset. A parse error throws the same exception basic_json::parse would throw for the same input, message and position included. detail::abi_config keeps JSON_STRICT_NUL_HANDLING and JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON readable after json.hpp undefines them, in the ABI namespace so they always match the basic_json in use. A NUL byte that ends a // comment is the end of the input, as in parse() since #5696. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
86 lines
2.9 KiB
C++
86 lines
2.9 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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/*!
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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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