Niels Lohmann 74f5ecbd35 accept() checks strings without copying them ...

json::accept() parses through json_sax_acceptor, which ignores the
values of strings and object keys, but the lexer still copied every
string token into its token buffer. That copy was 18 % of the
instructions of json::accept() on twitter.json (x86, GCC 16).

The lexer's flag for accept(), renamed from discard_number_values to
discard_values, now also selects a second instantiation of
scan_string() that performs the same checks (escapes, surrogates,
UTF-8, control characters, with the same error messages) without
writing to the token buffer. scan() chooses the instantiation once per
string: a run-time check inside the string loop made number-heavy
files up to 3 % slower on Apple M1.

json::accept() over 19 files, time after/before (geomean): 0.876 on x86
with GCC 16.2, 0.884 with Clang 23, 0.932 on Apple M1; up to 0.74 on
single files; files with few strings (canada, mesh, numbers) unchanged.

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

2026-10-31 00:07:57 +01:00

..

json_fwd.hpp

json_view: one SIMD macro set with the library (#5921)

2026-10-26 20:13:31 +01:00

json_literals.hpp

Move the user-defined string literals to <nlohmann/json_literals.hpp> and add JSON_NO_AUTOMATIC_UDLS (#5610)

2026-09-30 20:08:17 +02:00

json_view.hpp

Fix the red CI on develop: remove the duplicate is_editable in basic_json_view (#5966)

2026-10-30 16:48:31 +01:00

json.hpp

accept() checks strings without copying them

2026-10-31 00:07:57 +01:00