Niels Lohmann
73aea7ce54
* Add JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE to set the UBJSON whole-input budget The whole-input budget for the elements of optimized UBJSON arrays of type Z, T and F (1048576 plus 4 per byte read) rejects files written by 3.12.0 that have long arrays of these types, such as 1100 rows of 1000 nulls with a `$Z` annotation, and there was no way to read them. The per-byte rate is now the macro JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE. Semantics: - default 4, so the default build is unchanged (the generated code of from_ubjson is identical at -O2 up to source line numbers); - the value must be a positive integer: 0, negative, non-integral, bool, character and wider-than-uintmax_t values fail to compile with a static_assert that names the macro; - a value that does not fit into std::size_t is the largest size_t, so one spelling works for 32- and 64-bit targets; - the limit base + rate * bytes_read saturates at the largest size_t instead of wrapping around, for any rate and input size; a rate of 131072 (2^20 / 8) or more cannot be exceeded by any input (the shortest header of an array of more than 32767 elements is 8 bytes), which switches the whole-input budget off; - the limit of one array (1048576) and the base (1048576) stay fixed constants, so the writer fallback still follows the base only and a reader with any rate reads everything the writer produces; - the macro is not part of the ABI tag and must have the same value in every translation unit; it is documented that way. The memory the arrays can take in a DOM is about 20 bytes per rate and byte of input (measured, macOS, containers of 9 * rate elements: 25 bytes per input byte at rate 1, 81 at 4, 312 at 16, 1226 at 64, 5493 at 256) plus about 33 MB for the base. A 3.12.0 row of N values has a header of b bytes (5 up to 255, 6 up to 32767, 8 above), so a table is read completely if N <= rate * b, and otherwise up to (1048576 + h * rate, h = outer header: 6, 7 or 9 bytes) / (N - rate * b) rows; 1100 rows of 1000 nulls need a rate of 8. The new page of the macro documents the formulas, the measurements, and two examples that are run by the documentation checks. The tests of the budget move to tests/src/unit-ubjson_valueless.cpp, which derives every boundary from the macro and is built with the rates 1, 1000000 and 0xFFFFFFFFFFFFFFFF in addition to the default (the last two check that nothing is refused and that the limit does not wrap around); they fail with the unchanged header for rate 1, 1000000 and the maximum. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Refuse char8_t for JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE and clarify its documentation Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>
67 lines
2.0 KiB
C++
67 lines
2.0 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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// clean up
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#undef JSON_ASSERT
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#undef JSON_INTERNAL_CATCH
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#undef JSON_THROW
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#undef JSON_PRIVATE_UNLESS_TESTED
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#undef NLOHMANN_BASIC_JSON_TPL_DECLARATION
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#undef NLOHMANN_BASIC_JSON_TPL
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#undef JSON_EXPLICIT
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#undef NLOHMANN_CAN_CALL_STD_FUNC_IMPL
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#undef JSON_INLINE_VARIABLE
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#undef JSON_NO_UNIQUE_ADDRESS
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#undef JSON_DISABLE_ENUM_SERIALIZATION
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#undef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
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#undef JSON_UNLOCKED_FILE_IO
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#undef JSON_FILE_WINDOW
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#undef JSON_DTOA_SSE2
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#undef JSON_DTOA_NEON
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#undef JSON_LITTLE_ENDIAN_TARGET
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#undef JSON_BIG_ENDIAN_TARGET
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#undef JSON_SCAN_NEON
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#undef JSON_SCAN_SSE2
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#undef JSON_SCAN_SSSE3
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#undef JSON_SCAN_SSSE3_DISPATCH
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#undef JSON_SCAN_SSSE3_TARGET
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#undef JSON_SCAN_VECTOR
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#undef JSON_SCAN_VECTOR_UTF8
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#ifndef JSON_TEST_KEEP_MACROS
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#undef JSON_CATCH
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#undef JSON_TRY
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#undef JSON_HAS_CPP_11
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#undef JSON_HAS_CPP_14
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#undef JSON_HAS_CPP_17
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#undef JSON_HAS_CPP_20
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#undef JSON_HAS_CPP_23
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#undef JSON_HAS_CPP_26
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#undef JSON_HAS_FILESYSTEM
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#undef JSON_HAS_EXPERIMENTAL_FILESYSTEM
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#undef JSON_HAS_THREE_WAY_COMPARISON
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#undef JSON_HAS_RANGES
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#undef JSON_HAS_RANGE_VIEW_CONVERSION
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#undef JSON_HAS_STD_FORMAT
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#undef JSON_HAS_STATIC_RTTI
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#undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
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#undef JSON_BRACE_INIT_COPY_SEMANTICS
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#undef JSON_PRECISE_STREAM_POSITION
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#undef JSON_STRICT_NUL_HANDLING
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#undef JSON_STRICT_BINARY_UTF8
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#undef JSON_DELETE_DEPRECATED_FUNCTIONS
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#undef JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS
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#undef JSON_DISABLE_STREAM_BULK_SCAN
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#undef JSON_DISABLE_UNLOCKED_FILE_IO
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#undef JSON_UBJSON_VALUELESS_ELEMENTS_PER_BYTE
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#endif
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#include <nlohmann/thirdparty/hedley/hedley_undef.hpp>
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