Niels Lohmann ba25f96169 Reserve the storage of an ordered_json in flatten() once ...

flatten() appended the entries to an ordered_map one by one, so its vector
grew by doubling and moved every entry about once in total. The number of
entries is known after a walk over the value that only counts (it needs no
path strings), so objects with a reserve() are given that capacity first.
std::map has no reserve() and is unchanged.

flatten() of an ordered_json (instructions on macOS, Linux Ir GCC 13 / Clang 18):
citm_catalog 36.8M -> 23.1M, 32.7M -> 17.1M / 31.7M -> 16.8M; twitter 20.5M ->
13.6M, 17.6M -> 10.0M / 17.0M -> 9.8M. Output is identical.

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

2026-10-22 09:29:49 +02:00

..

json_fwd.hpp

Scan strings with SSE2, SSSE3, or NEON (#5853)

2026-10-21 20:00:50 +02:00

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

Use standard library helpers where available, with C++11 fallbacks (#5876)

2026-10-21 20:14:59 +02:00

json.hpp

Reserve the storage of an ordered_json in flatten() once

2026-10-22 09:29:49 +02:00