amorfo77/json
1
0 Fork 0
mirror of https://github.com/nlohmann/json.git synced 2026-10-22 22:08:55 +00:00
Code Issues Packages Projects Releases Wiki Activity

Reserve at least 64 bytes for the result of a binary serialization

Browse Source 
The result of to_cbor() and its siblings reserved the lower bound of
binary_reserve_hint(), for a small object a few bytes, and the first write of
the sink replaced it by an allocation of 64 bytes, as an empty or too small
vector is grown to at least that. A small document therefore cost two
allocations and a free.

The result now reserves at least min_vector_sink_capacity (64) characters at
once. binary_reserve_hint() itself, a lower bound that is tested as such, is
unchanged.

Instructions to serialize a small object (six members, a nested array and object), Linux, GCC 13: to_cbor 1700 -> 1500, to_msgpack 1800 -> 1600, to_ubjson 1800 -> 1700, to_bson 2700 -> 2500. Documents larger than 64 bytes of hint are unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann committed 2026-10-22 09:29:11 +02:00
1 parent 7241ba94c8
commit ceb3c92709
4 files changed
+54 -18
Download Patch File Download Diff File Expand all files Collapse all files

No files matched your search

include/nlohmann/json.hpp
+6 -6
View File
@@ -6321,7 +6321,7 @@ public:
const error_handler_t error_handler = detail::binary_writer_default_error_handler())
{
std::vector<std::uint8_t> result;
result.reserve(detail::binary_reserve_hint(j));
result.reserve(detail::binary_initial_capacity(j));
vector_writer(result, error_handler).write_cbor(j);
return result;
}
@@ -6352,7 +6352,7 @@ public:
const error_handler_t error_handler = error_handler_t::keep)
{
std::vector<std::uint8_t> result;
result.reserve(detail::binary_reserve_hint(j));
result.reserve(detail::binary_initial_capacity(j));
vector_writer(result, error_handler).write_msgpack(j);
return result;
}
@@ -6385,7 +6385,7 @@ public:
const error_handler_t error_handler = detail::binary_writer_default_error_handler())
{
std::vector<std::uint8_t> result;
result.reserve(detail::binary_reserve_hint(j));
result.reserve(detail::binary_initial_capacity(j));
vector_writer(result, error_handler).write_ubjson(j, use_size, use_type);
return result;
}
@@ -6421,7 +6421,7 @@ public:
const error_handler_t error_handler = detail::binary_writer_default_error_handler())
{
std::vector<std::uint8_t> result;
result.reserve(detail::binary_reserve_hint(j));
result.reserve(detail::binary_initial_capacity(j));
vector_writer(result, error_handler).write_ubjson(j, use_size, use_type, true, true, version);
return result;
}
@@ -6456,7 +6456,7 @@ public:
const error_handler_t error_handler = detail::binary_writer_default_error_handler())
{
std::vector<std::uint8_t> result;
result.reserve(detail::binary_reserve_hint(j));
result.reserve(detail::binary_initial_capacity(j));
vector_writer(result, error_handler).write_bson(j);
return result;
}
@@ -6486,7 +6486,7 @@ public:
static std::vector<std::uint8_t> to_bon8(const basic_json& j)
{
std::vector<std::uint8_t> result;
result.reserve(detail::binary_reserve_hint(j));
result.reserve(detail::binary_initial_capacity(j));
vector_writer(result).write_bon8(j);
return result;
}