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Niels Lohmann 4da932f518 Make parsing from std::istream and FILE* fast (#5828 )

* Make parsing from std::istream and FILE* fast

Squashed onto develop cd6b428ef (CI fixes from #5860). Original commits:

- Let the lexer's bulk fast paths run on a window of the input
- Scan the get area of an input stream in bulk
- Lock a FILE once per parse instead of once per character
- Add benchmarks for parsing from a FILE* and for many values from a stream
- Avoid implicit unsigned char to char conversion in stream tests
- Make file_input_adapter::unlock() safe to call on a moved-from adapter

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Add ABI tags for JSON_DISABLE_STREAM_BULK_SCAN and JSON_DISABLE_UNLOCKED_FILE_IO

Both macros select between two definitions of an input adapter, so
translation units compiled with different settings violated the ODR when
linked together. Like the other ABI-affecting macros, they now append a
tag to the inline namespace: _dsbs and _dufio. Their defaults move to
abi_macros.hpp so that json_fwd.hpp sees them, and the natvis file is
regenerated for the new namespaces.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Skip the exception-only checks of the stream input tests without exceptions

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

2026-10-19 22:00:58 +02:00

8.8 KiB

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Macros

Some aspects of the library can be configured by defining preprocessor macros before including the json.hpp header. See also the macro overview page.

Runtime assertions

JSON_ASSERT(x) - control behavior of runtime assertions

Exceptions

JSON_CATCH_USER(exception)
JSON_THROW_USER(exception)
JSON_TRY_USER - control exceptions
JSON_DIAGNOSTICS - control extended diagnostics
JSON_DIAGNOSTIC_POSITIONS - access positions of elements
JSON_NOEXCEPTION - switch off exceptions

Parsing

JSON_DISABLE_STREAM_BULK_SCAN - read a std::istream one character at a time instead of scanning its stream buffer in bulk
JSON_DISABLE_UNLOCKED_FILE_IO - read a FILE* with std::fgetc instead of locking it once and using the unlocked stdio functions
JSON_PRECISE_STREAM_POSITION - opt in to leaving an input stream positioned right after a parsed number
JSON_STRICT_BINARY_UTF8 - opt in to checking strings for valid UTF-8 in the CBOR, UBJSON, BJData, and BSON writers
JSON_STRICT_NUL_HANDLING - opt in to rejecting a NUL byte in the input instead of treating it as end of input

Language support

JSON_HAS_CPP_11
JSON_HAS_CPP_14
JSON_HAS_CPP_17
JSON_HAS_CPP_20 - set supported C++ standard
JSON_HAS_FILESYSTEM
JSON_HAS_EXPERIMENTAL_FILESYSTEM - control std::filesystem support
JSON_HAS_RANGE_VIEW_CONVERSION - control construction from std::ranges views
JSON_HAS_RANGES - control std::ranges support
JSON_HAS_STATIC_RTTI - control RTTI (run time type information) support
JSON_HAS_STD_FORMAT - control std::format/std::formatter support
JSON_HAS_THREE_WAY_COMPARISON - control 3-way comparison support
JSON_NO_AUTOMATIC_UDLS - do not include the user-defined string literals (UDLs) automatically
JSON_NO_IO - switch off functions relying on certain C++ I/O headers
JSON_NO_THREAD_LOCAL - switch off the use of thread_local storage
JSON_SKIP_UNSUPPORTED_COMPILER_CHECK - do not warn about unsupported compilers
JSON_USE_GLOBAL_UDLS - place user-defined string literals (UDLs) into the global namespace
JSON_USE_SIMDUTF - use the simdutf library to accelerate UTF-8 validation

Library version

JSON_SKIP_LIBRARY_VERSION_CHECK - skip library version check
NLOHMANN_JSON_VERSION_MAJOR
NLOHMANN_JSON_VERSION_MINOR
NLOHMANN_JSON_VERSION_PATCH - library version information

Library namespace

NLOHMANN_JSON_NAMESPACE - full name of the nlohmann namespace
NLOHMANN_JSON_NAMESPACE_BEGIN
NLOHMANN_JSON_NAMESPACE_END - open and close the library namespace
NLOHMANN_JSON_NAMESPACE_NO_VERSION - disable the version component of the inline namespace

Type conversions

JSON_BRACE_INIT_COPY_SEMANTICS - opt in to copy/move semantics for single-element brace initialization
JSON_DISABLE_ENUM_SERIALIZATION - switch off default serialization/deserialization functions for enums
JSON_DISABLE_TUPLE_REFERENCE_CONVERSION - switch off conversion from a one-element tuple of a JSON reference
JSON_USE_IMPLICIT_CONVERSIONS - control implicit conversions
JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS - opt in to storing maps with enum keys as objects

Deprecated functions

JSON_DELETE_DEPRECATED_FUNCTIONS - opt in to deleting the deprecated functions ahead of their removal in version 4.0.0

Comparison behavior

JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON - control comparison of discarded values

Serialization/deserialization macros

Enums

NLOHMANN_JSON_SERIALIZE_ENUM - serialize/deserialize an enum
NLOHMANN_JSON_SERIALIZE_ENUM_STRICT - serialize/deserialize an enum with exceptions

Classes and structs

NLOHMANN_DEFINE_TYPE_INTRUSIVE - serialize/deserialize a non-derived class with private members
NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT - serialize/deserialize a non-derived class with private members; uses default values
NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE - serialize a non-derived class with private members
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE - serialize/deserialize a non-derived class
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT - serialize/deserialize a non-derived class; uses default values
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE - serialize a non-derived class
NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE - serialize/deserialize a derived class with private members
NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT - serialize/deserialize a derived class with private members; uses default values
NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE - serialize a derived class with private members
NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE - serialize/deserialize a derived class
NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT - serialize/deserialize a derived class; uses default values
NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE - serialize a derived class
NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES - serialize/deserialize a non-derived class with private members; uses custom names
NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES - serialize/deserialize a non-derived class with private members; uses default values; uses custom names
NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - serialize a non-derived class with private members; uses custom names
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES - serialize/deserialize a non-derived class; uses custom names
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES - serialize/deserialize a non-derived class; uses default values; uses custom names
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - serialize a non-derived class; uses custom names
NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES - serialize/deserialize a derived class with private members; uses custom names
NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES - serialize/deserialize a derived class with private members; uses default values; uses custom names
NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - serialize a derived class with private members; uses custom names
NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES - serialize/deserialize a derived class; uses custom names
NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES - serialize/deserialize a derived class; uses default values; uses custom names
NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - serialize a derived class; uses custom names

8.8 KiB Raw Blame History