mirror of
https://github.com/nlohmann/json.git
synced 2026-10-07 15:07:13 +00:00
Niels Lohmann
759dd2e1b1
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++
// __ _____ _____ _____
|
|
// __| | __| | | | JSON for Modern C++
|
|
// | | |__ | | | | | | version 3.12.0
|
|
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
|
|
//
|
|
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
|
|
// SPDX-License-Identifier: MIT
|
|
|
|
#pragma once
|
|
|
|
#include <algorithm> // min
|
|
#include <cstddef> // size_t
|
|
#include <string> // string
|
|
|
|
#include <nlohmann/json.hpp>
|
|
#include <nlohmann/detail/view/builder.hpp>
|
|
#include <nlohmann/detail/view/macro_scope.hpp>
|
|
|
|
NLOHMANN_JSON_NAMESPACE_BEGIN
|
|
namespace detail
|
|
{
|
|
namespace view
|
|
{
|
|
|
|
// Exceptions are thrown out of line, so that the accessors that may throw stay
|
|
// small enough to be inlined.
|
|
|
|
[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_type_error(int id, const char* prefix, const char* type)
|
|
{
|
|
NLOHMANN_VIEW_THROW(type_error::create(id, concat(prefix, type), nullptr));
|
|
}
|
|
|
|
[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_out_of_range(int id, const std::string& msg)
|
|
{
|
|
NLOHMANN_VIEW_THROW(out_of_range::create(id, msg, nullptr));
|
|
}
|
|
|
|
[[noreturn]] NLOHMANN_VIEW_NOINLINE inline void throw_invalid_iterator(int id, const char* msg)
|
|
{
|
|
NLOHMANN_VIEW_THROW(invalid_iterator::create(id, msg, nullptr));
|
|
}
|
|
|
|
/*!
|
|
@brief throw the exception BasicJsonType::parse would throw for this input
|
|
|
|
The view accepts exactly the inputs parse() accepts, so on a failure the
|
|
library parser is run on the same bytes: it throws the exception parse() would
|
|
throw, with the same message, position, and "last read" token. The error path
|
|
is cold, so this costs nothing on valid input. Should parse() accept the input
|
|
nevertheless (a bug), the view's own failure is reported.
|
|
*/
|
|
template<typename BasicJsonType>
|
|
[[noreturn]] NLOHMANN_VIEW_NOINLINE void throw_parse_failure(const parse_failure& f, const char* src, std::size_t size,
|
|
bool ignore_comments, bool ignore_trailing_commas)
|
|
{
|
|
if (f.code == error_code::input_too_large)
|
|
{
|
|
// LCOV_EXCL_START (4 GiB)
|
|
NLOHMANN_VIEW_THROW(out_of_range::create(416, "input of 4 GiB or more is not supported by json_document", nullptr));
|
|
// LCOV_EXCL_STOP
|
|
}
|
|
const BasicJsonType accepted = BasicJsonType::parse(src, src + size, nullptr, true, ignore_comments, ignore_trailing_commas);
|
|
// LCOV_EXCL_START (only if parse() accepts what the view rejects: a bug)
|
|
static_cast<void>(accepted);
|
|
|
|
position_t pos;
|
|
const std::size_t off = (std::min)(f.offset, size);
|
|
pos.chars_read_total = off + 1;
|
|
std::size_t line_start = 0;
|
|
for (std::size_t i = 0; i < off; ++i)
|
|
{
|
|
if (src[i] == '\n')
|
|
{
|
|
++pos.lines_read;
|
|
line_start = i + 1;
|
|
}
|
|
}
|
|
pos.chars_read_current_line = off + 1 - line_start;
|
|
NLOHMANN_VIEW_THROW(parse_error::create(101, pos, "syntax error while parsing value", nullptr));
|
|
// LCOV_EXCL_STOP
|
|
}
|
|
|
|
} // namespace view
|
|
} // namespace detail
|
|
NLOHMANN_JSON_NAMESPACE_END
|