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Stop allocating the BJData excluded-marker list per container (#5555)

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write_ubjson() built a std::vector of the eight markers BJData forbids as
the type of an optimized container - one heap allocation plus a linear
search for every array and object it wrote with use_type, even for plain
UBJSON output, where the list isn't consulted. The list was also spelled
out twice. A constexpr helper, is_bjdata_excluded_type_marker(), replaces
both.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-24 17:04:44 +02:00
committed by GitHub
parent 5f659c881a
commit 8699de3064
2 changed files with 34 additions and 12 deletions
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23
include/nlohmann/detail/output/binary_writer.hpp
View File

@@ -881,8 +881,6 @@ class binary_writer
return ubjson_prefix(v, use_bjdata) == first_prefix;
});
std::vector<CharType> bjdx = {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z'}; // excluded markers in bjdata optimized type
// an optimized array of a valueless type carries no payload, so a
// reader has nothing but the declared count to bound the allocation
// by and refuses an excessive one. Write the unoptimized form for
@@ -893,7 +891,7 @@ class binary_writer
&& j.m_data.m_value.array->size() > detail::max_valueless_container_size;
if (same_prefix && !excessive_valueless
&& !(use_bjdata && std::find(bjdx.begin(), bjdx.end(), first_prefix) != bjdx.end()))
&& !(use_bjdata && is_bjdata_excluded_type_marker(first_prefix)))
{
prefix_required = false;
oa.write_character(to_char_type('$'));
@@ -997,9 +995,7 @@ class binary_writer
return ubjson_prefix(v, use_bjdata) == first_prefix;
});
std::vector<CharType> bjdx = {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z'}; // excluded markers in bjdata optimized type
if (same_prefix && !(use_bjdata && std::find(bjdx.begin(), bjdx.end(), first_prefix) != bjdx.end()))
if (same_prefix && !(use_bjdata && is_bjdata_excluded_type_marker(first_prefix)))
{
prefix_required = false;
oa.write_character(to_char_type('$'));
@@ -1726,6 +1722,21 @@ class binary_writer
}
}
/*!
@brief whether BJData forbids @a marker as the type of an optimized array
or object
Containers, strings, high-precision numbers, booleans and null cannot be
declared as the single type of an optimized container in BJData; such a
container is written unoptimized. The reader rejects them with the same
list (binary_reader::bjd_optimized_type_markers).
*/
static constexpr bool is_bjdata_excluded_type_marker(const CharType marker) noexcept
{
return marker == '[' || marker == '{' || marker == 'S' || marker == 'H'
|| marker == 'T' || marker == 'F' || marker == 'N' || marker == 'Z';
}
static constexpr CharType get_ubjson_float_prefix(float /*unused*/)
{
return 'd'; // float 32

23
single_include/nlohmann/json.hpp
View File

@@ -19745,8 +19745,6 @@ class binary_writer
return ubjson_prefix(v, use_bjdata) == first_prefix;
});
std::vector<CharType> bjdx = {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z'}; // excluded markers in bjdata optimized type
// an optimized array of a valueless type carries no payload, so a
// reader has nothing but the declared count to bound the allocation
// by and refuses an excessive one. Write the unoptimized form for
@@ -19757,7 +19755,7 @@ class binary_writer
&& j.m_data.m_value.array->size() > detail::max_valueless_container_size;
if (same_prefix && !excessive_valueless
&& !(use_bjdata && std::find(bjdx.begin(), bjdx.end(), first_prefix) != bjdx.end()))
&& !(use_bjdata && is_bjdata_excluded_type_marker(first_prefix)))
{
prefix_required = false;
oa.write_character(to_char_type('$'));
@@ -19861,9 +19859,7 @@ class binary_writer
return ubjson_prefix(v, use_bjdata) == first_prefix;
});
std::vector<CharType> bjdx = {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z'}; // excluded markers in bjdata optimized type
if (same_prefix && !(use_bjdata && std::find(bjdx.begin(), bjdx.end(), first_prefix) != bjdx.end()))
if (same_prefix && !(use_bjdata && is_bjdata_excluded_type_marker(first_prefix)))
{
prefix_required = false;
oa.write_character(to_char_type('$'));
@@ -20590,6 +20586,21 @@ class binary_writer
}
}
/*!
@brief whether BJData forbids @a marker as the type of an optimized array
or object
Containers, strings, high-precision numbers, booleans and null cannot be
declared as the single type of an optimized container in BJData; such a
container is written unoptimized. The reader rejects them with the same
list (binary_reader::bjd_optimized_type_markers).
*/
static constexpr bool is_bjdata_excluded_type_marker(const CharType marker) noexcept
{
return marker == '[' || marker == '{' || marker == 'S' || marker == 'H'
|| marker == 'T' || marker == 'F' || marker == 'N' || marker == 'Z';
}
static constexpr CharType get_ubjson_float_prefix(float /*unused*/)
{
return 'd'; // float 32