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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>
72 lines
2.9 KiB
C++
72 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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// Macros of json_view.hpp and its detail headers. json.hpp undefines its own
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// macros at its end (macro_unscope.hpp), so the view defines the few it needs
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// under its own prefix; json_view.hpp undefines them all at its end
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// (detail/view/macro_unscope.hpp). Configuration that json.hpp undefines is
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// read from detail::abi_config instead.
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#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
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#define NLOHMANN_VIEW_HAS_CPP_17 1
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#else
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#define NLOHMANN_VIEW_HAS_CPP_17 0
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#endif
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#if defined(__GNUC__) || defined(__clang__)
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#define NLOHMANN_VIEW_LIKELY(x) __builtin_expect(!!(x), 1)
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#define NLOHMANN_VIEW_UNLIKELY(x) __builtin_expect(!!(x), 0)
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#define NLOHMANN_VIEW_ALWAYS_INLINE inline __attribute__((always_inline))
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#define NLOHMANN_VIEW_NOINLINE __attribute__((noinline))
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#elif defined(_MSC_VER)
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#define NLOHMANN_VIEW_LIKELY(x) (x)
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#define NLOHMANN_VIEW_UNLIKELY(x) (x)
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#define NLOHMANN_VIEW_ALWAYS_INLINE __forceinline
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#define NLOHMANN_VIEW_NOINLINE __declspec(noinline)
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#else
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#define NLOHMANN_VIEW_LIKELY(x) (x)
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#define NLOHMANN_VIEW_UNLIKELY(x) (x)
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#define NLOHMANN_VIEW_ALWAYS_INLINE inline
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#define NLOHMANN_VIEW_NOINLINE
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#endif
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#if defined(__GNUC__) || defined(__clang__)
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#define NLOHMANN_VIEW_NODISCARD __attribute__((warn_unused_result))
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#elif defined(_MSC_VER)
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#define NLOHMANN_VIEW_NODISCARD _Check_return_
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#else
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#define NLOHMANN_VIEW_NODISCARD
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#endif
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// exceptions as in json.hpp (JSON_NOEXCEPTION, JSON_THROW_USER)
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#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && !defined(JSON_NOEXCEPTION)
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#define NLOHMANN_VIEW_THROW(exception) throw exception
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#else
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#include <cstdlib>
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// (the exception is built first, so that the arguments of the throwing
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// helpers count as used; the program ends anyway)
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#define NLOHMANN_VIEW_THROW(exception) (static_cast<void>(exception), std::abort())
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#endif
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#if defined(JSON_THROW_USER)
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#undef NLOHMANN_VIEW_THROW
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#define NLOHMANN_VIEW_THROW JSON_THROW_USER
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#endif
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// the parser stores a node's first word at once where the layout of `node` is
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// known to be little-endian (MSVC targets are); elsewhere field by field
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#if (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__) || defined(_MSC_VER)
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#define NLOHMANN_VIEW_LITTLE_ENDIAN 1
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#else
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#define NLOHMANN_VIEW_LITTLE_ENDIAN 0
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#endif
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/// sixteen checks at fixed offsets 0..15
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#define NLOHMANN_VIEW_REPEAT16(X) X(0) X(1) X(2) X(3) X(4) X(5) X(6) X(7) X(8) X(9) X(10) X(11) X(12) X(13) X(14) X(15)
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