Niels Lohmann e29ac4f043 Reserve capacity in from_json() object conversion when supported ...

The object-to-container from_json() overload filled the target
container one element at a time without reserving capacity, even
when the target type supports reserve() (e.g. std::unordered_map)
and the number of elements is already known. This caused unnecessary
rehashing while parsing large objects into such containers.

Add a reserve-detecting overload (from_json_object_impl), mirroring
the priority_tag-based SFINAE technique already used by the array
conversion path (from_json_array_impl), so that reserve(size()) is
called up front when available and the loop falls back unchanged
otherwise (e.g. for std::map).

Fixes #5406

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

2026-09-05 20:43:23 +02:00

..

json_fwd.hpp

📄 adjust year (#5044)

2026-01-01 20:00:39 +01:00

json.hpp

Reserve capacity in from_json() object conversion when supported

2026-09-05 20:43:23 +02:00