* Devirtualize binary_writer via a value-type output sink
to_cbor/to_msgpack/to_ubjson/to_bjdata/to_bson wrote every byte through
output_adapter_t, a shared_ptr<output_adapter_protocol> whose
write_character/write_characters are virtual. Unlike the lexer (templated
on a concrete InputAdapterType), the binary writer never got that
treatment, so binary output paid a vtable lookup per byte and a
make_shared per call.
Template binary_writer on an OutputSinkType and give it two concrete,
non-virtual sinks:
- output_vector_sink: appends straight into a std::vector (push_back /
insert), used by the vector-returning to_* convenience functions. No
vtable, no shared_ptr; the writes inline.
- output_adapter_sink: forwards to a type-erased output_adapter_t, so the
existing to_*(j, output_adapter) overloads (streams, strings, custom
adapters) keep working exactly as before -- one virtual call each,
unchanged.
binary_writer keeps a convenience constructor taking output_adapter_t
(building the default output_adapter_sink), so the adapter overloads are
untouched; only the convenience functions switch to the vector sink. The
friend declaration and the basic_json binary_writer alias gain the new
(defaulted) template parameter.
Output is byte-for-byte identical: verified across ~3000 randomized
values plus curated edge cases (all scalar widths, strings with invalid
UTF-8, binary, nested arrays/objects) for CBOR, MessagePack, UBJSON (both
size/type settings), BJData, and BSON, plus the output_adapter path, in
C++11/17/20. Warning-clean under clang -Weverything and the gcc pedantic
set; clang-tidy clean on the changed headers; make check-amalgamation
clean.
Throughput (g++ -O3, vs develop): scalar-dense binary output such as
integer arrays ~1.4x; many small to_cbor calls ~1.04x (DOM traversal
bound); string/blob-heavy output unchanged (already bulk-bound). No
workload regressed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAYM1qhSA2FDaDcGfPW3fG
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI failures from binary_writer output-sink change
Four CI jobs failed on the initial commit; all are addressed here without
changing any output (binary encodings remain byte-for-byte identical to
develop across the differential corpus):
1. ci_test_gcc / cuda (-Werror=duplicated-branches): for number_float_t ==
float, static_cast<float>(n) is the identity, so write_compact_float's
two branches are intentionally identical. Once the concrete vector sink
is inlined, GCC constant-folds and diagnoses this (the type-erased path
hid it behind a non-inlined virtual call). Silence -Wduplicated-branches
for GCC (clang has no such warning) alongside the existing -Wfloat-equal
pragma.
2. ci_static_analysis_clang (UBSan nonnull-attribute): binary_writer passes
a null pointer with length 0 for empty strings/binary. output_vector_sink
/ output_adapter_sink declared write_characters JSON_HEDLEY_NON_NULL, so
the sanitizer flagged the (harmless) zero-length call once the sink was
called directly rather than through the attribute-free virtual base. Drop
the attribute from both sinks, matching the pre-existing behavior.
3. ci_cpplint (build/include_what_you_use): output_adapter_sink uses
std::move; add #include <utility>.
4. ci_cuda_example (nvcc 11.8): NVCC's front end rejects the default
template argument on the binary_writer alias template. Revert the alias
to its original single-parameter form (relying on binary_writer's own
defaulted OutputSinkType) and spell out the full type in the vector-sink
convenience functions.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAYM1qhSA2FDaDcGfPW3fG
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Encode big-endian numbers with a byte swap instead of std::reverse
write_number() reordered multi-byte numbers for the big-endian formats
(CBOR/MessagePack/UBJSON) with std::reverse over the byte array. GCC
lowered only some sizes to a bswap; clang kept a scalar byte shuffle
(0 bswap instructions in the CBOR number path). Replace the reverse with
size-dispatched __builtin_bswap16/32/64 helpers (portable shift fallback
for other compilers; std::reverse retained for exotic sizes such as a
long double number_float_t).
Codegen: the CBOR number path now emits bswap on both compilers
(gcc 2 -> 16, clang 0 -> 4). Output is byte-for-byte identical to the
previous implementation across the binary differential corpus.
Throughput (isolated vs the std::reverse version, best of 9):
CBOR int64 array gcc +7% clang +10%
CBOR uint16 array gcc +27% clang flat
Modest but consistent on number-dense encodings; negligible on
string/blob-heavy output, as expected.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAYM1qhSA2FDaDcGfPW3fG
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Reserve output capacity up front for binary serialization
The vector-returning to_cbor/to_msgpack/to_ubjson/to_bjdata/to_bson grew
the output buffer purely by geometric reallocation. Reserving an estimate
up front avoids the early reallocations, which is the dominant per-byte
cost for array/object-heavy output.
The estimate (binary_reserve_hint) is deliberately conservative and safe
against untrusted input: it consults only the top-level element count
(O(1), no walk of the DOM), guards the multiplication against overflow,
and clamps the result to a fixed 1 MiB ceiling, so a large or hostile DOM
can never force an oversized allocation here. The buffer still grows
geometrically past the hint, so an underestimate only costs a few later
reallocations; scalars/strings/binary are written in one shot and get no
hint. Reserving capacity does not change the bytes produced.
Throughput (g++/clang -O3, vs the previous commit):
cbor int array +10% / +13%
cbor object array +20% / +38%
Output is byte-for-byte identical to develop across the binary
differential corpus.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAYM1qhSA2FDaDcGfPW3fG
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Address review findings on the binary writer output sinks
- binary_reserve_hint(): the 4-bytes-per-element estimate over-reserved by up
to 4x for arrays of small scalars (CBOR encodes 0..23 in one byte), and the
returned vector kept that capacity. Make the hint a strict lower bound on the
encoded size instead, which also removes the 1 MiB clamp whose branch no test
could reach (the largest container in the suite has 65793 elements).
- Guard the -Wduplicated-branches pragma with __GNUC__ >= 7. The warning does
not exist before GCC 7, so naming it made GCC 4.8/4.9/5/6 - which the CI
matrix still builds - warn under -Wpragmas on every including translation
unit, breaking downstream -Werror builds.
- Constrain the adapter constructor of binary_writer with the enable_if its
documentation already claimed, so a writer over some other sink type is no
longer advertised as constructible from an output adapter.
- Let output_vector_adapter wrap output_vector_sink rather than duplicating the
append logic, so the type-erased and templated paths share one implementation.
- Collapse the three copies of the memcpy/byte_swap/memcpy dance into a single
byte_swap_buffer() helper, and add the MSVC _byteswap_* intrinsics so MSVC no
longer falls back to the scalar shuffle this change exists to eliminate.
- Add a vector_writer() helper for the five vector-returning to_* overloads
instead of spelling out the writer type at each call site, and drop a dead
default member initializer on output_adapter_sink.
- New tests: the vector sink and the adapter sink must produce identical bytes
for every format (the two to_* overloads no longer delegate to each other and
could otherwise drift), and binary_reserve_hint() must never exceed the size
actually written.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Route the -Wduplicated-branches pragma through Hedley
Match #5485, which moved the binary writer's hand-rolled diagnostic
pragmas onto JSON_HEDLEY_PRAGMA (merged into develop while this branch
was open). The devirtualization's -Wduplicated-branches suppression in
write_compact_float was the one raw '#pragma GCC diagnostic' left; it
now uses JSON_HEDLEY_PRAGMA like the adjacent -Wfloat-equal line, still
guarded to GCC >= 7 and non-clang (the warning exists only there).
Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAYM1qhSA2FDaDcGfPW3fG
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
* Add versioned inline namespace
Add a versioned inline namespace to prevent ABI issues when linking code
using multiple library versions.
* Add namespace macros
* Encode ABI information in inline namespace
Add _diag suffix to inline namespace if JSON_DIAGNOSTICS is enabled, and
_ldvcmp suffix if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON is enabled.
* Move ABI-affecting macros into abi_macros.hpp
* Move std_fs namespace definition into std_fs.hpp
* Remove std_fs namespace from unit test
* Format more files in tests directory
* Add unit tests
* Update documentation
* Fix GDB pretty printer
* fixup! Add namespace macros
* Derive ABI prefix from NLOHMANN_JSON_VERSION_*
* Add benchmark for cbor serialization and cbor binary data serialization
* Use std::vector::insert method instead of std::copy in output_vector_adapter::write_characters
This change increases a lot the performance when writing lots of binary data.
* Rename 'develop' folder to 'include/nlohmann'
* Rename 'src' folder to 'single_include/nlohmann'
* Use <nlohmann/*> headers in sources and tests
* Change amalgamate config file
Niels LohmannandClaude
Florian Albrechtskirchinger
Romain Reignier
Niels Lohmann
David Pfahler
David Pfahler
Vitaliy Manushkin
Théo DELRIEU