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2.1.3, 2.1.8: one UBJSON container start helper, shared frame base (#5891)

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write_ubjson_start_array/_object are now write_ubjson_start_container<IsArray>,
keeping the array-only begin()+1 scan and excessive_valueless rule.
ubjson_frame derives from binary_container_frame instead of duplicating it.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann committed 2026-10-23 10:29:09 +02:00
1 parent 379bf8eddb
commit 48bd677617
1 file changed
+32 -72
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include/nlohmann/detail/output/binary_writer.hpp
+32 -72
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@@ -626,7 +626,7 @@ class binary_writer
case value_t::array:
{
bool prefix_required = true;
const bool write_closer = write_ubjson_start_array(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
const bool write_closer = write_ubjson_start_container<true>(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
{
const auto& array = *j.m_data.m_value.array;
@@ -704,7 +704,7 @@ class binary_writer
}
bool prefix_required = true;
const bool write_closer = write_ubjson_start_object(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
const bool write_closer = write_ubjson_start_container<false>(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
write_ubjson_members(j, use_count, use_type, prefix_required, use_bjdata, bjdata_version, depth);
@@ -967,9 +967,10 @@ class binary_writer
write_msgpack_container_prefix(N, j, 0x80, 0xDE, 0xDF);
}
/// @brief a CBOR, MessagePack, or BON8 array or object whose elements
/// @ref write_cbor_iterative, @ref write_msgpack_iterative, or
/// @ref write_bon8_iterative is still writing
/// @brief a CBOR, MessagePack, BON8, or (as the base of @ref ubjson_frame)
/// UBJSON array or object whose elements @ref write_container_iterative,
/// @ref write_bon8_iterative, or @ref write_ubjson_iterative is still
/// writing
struct binary_container_frame
{
explicit binary_container_frame(const BasicJsonType* value_) noexcept
@@ -1156,24 +1157,34 @@ class binary_writer
write_container_iterative<msgpack_walk>(root);
}
/// @return true when a closing ']' still has to be written after the elements
bool write_ubjson_start_array(const BasicJsonType& j, const bool use_count, const bool use_type,
const bool add_prefix, const bool use_bjdata, bool& prefix_required)
/*!
@brief write the start of an array (@a IsArray) or object: its opening
marker, the optimized type, and the count
@return true when a closing ']' or '}' still has to be written after the
elements
*/
template<bool IsArray>
bool write_ubjson_start_container(const BasicJsonType& j, const bool use_count, const bool use_type,
const bool add_prefix, const bool use_bjdata, bool& prefix_required)
{
prefix_required = true;
if (add_prefix)
{
oa.write_character(to_char_type('['));
oa.write_character(to_char_type(IsArray ? '[' : '{'));
}
if (use_type && !j.m_data.m_value.array->empty())
const std::size_t size = IsArray ? j.m_data.m_value.array->size() : j.m_data.m_value.object->size();
if (use_type && size != 0)
{
if (!use_count)
{
throw_size_marker_required(j);
}
const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
const bool same_prefix = std::all_of(j.begin() + 1, j.end(),
// the first element of an array has been compared with itself
const bool same_prefix = std::all_of(IsArray ? j.begin() + 1 : j.begin(), j.end(),
[this, first_prefix, use_bjdata](const BasicJsonType & v)
{
return ubjson_prefix(v, use_bjdata) == first_prefix;
@@ -1185,8 +1196,9 @@ class binary_writer
// those, at one byte per element, so the result can be read back.
// Objects are not affected: every element is preceded by its key.
const bool valueless_type = (first_prefix == 'Z' || first_prefix == 'T' || first_prefix == 'F');
const bool excessive_valueless = valueless_type
&& j.m_data.m_value.array->size() > detail::max_valueless_container_size;
const bool excessive_valueless = IsArray
&& valueless_type
&& size > detail::max_valueless_container_size;
if (same_prefix && !excessive_valueless
&& !(use_bjdata && is_bjdata_excluded_type_marker(first_prefix)))
@@ -1199,46 +1211,7 @@ class binary_writer
if (use_count)
{
write_ubjson_count(j.m_data.m_value.array->size(), use_bjdata);
}
return !use_count;
}
/// @return true when a closing '}' still has to be written after the elements
bool write_ubjson_start_object(const BasicJsonType& j, const bool use_count, const bool use_type,
const bool add_prefix, const bool use_bjdata, bool& prefix_required)
{
prefix_required = true;
if (add_prefix)
{
oa.write_character(to_char_type('{'));
}
if (use_type && !j.m_data.m_value.object->empty())
{
if (!use_count)
{
throw_size_marker_required(j);
}
const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
const bool same_prefix = std::all_of(j.begin(), j.end(),
[this, first_prefix, use_bjdata](const BasicJsonType & v)
{
return ubjson_prefix(v, use_bjdata) == first_prefix;
});
if (same_prefix && !(use_bjdata && is_bjdata_excluded_type_marker(first_prefix)))
{
prefix_required = false;
oa.write_character(to_char_type('$'));
oa.write_character(first_prefix);
}
}
if (use_count)
{
write_ubjson_count(j.m_data.m_value.object->size(), use_bjdata);
write_ubjson_count(size, use_bjdata);
}
return !use_count;
@@ -1266,21 +1239,12 @@ class binary_writer
/// @brief an object or array @ref write_ubjson_iterative is still writing
/// the elements of
struct ubjson_frame
struct ubjson_frame : binary_container_frame
{
ubjson_frame(const BasicJsonType* value_, const bool prefix_required_) noexcept
: value(value_)
: binary_container_frame(value_)
, prefix_required(prefix_required_)
{
if (value->is_object())
{
object_it = value->m_data.m_value.object->cbegin();
}
else
{
array_it = value->m_data.m_value.array->cbegin();
}
}
{}
// declared for GCC's -Weffc++, which asks for them in a class with
// pointer members and a non-trivial destructor; the exception
@@ -1292,13 +1256,9 @@ class binary_writer
ubjson_frame& operator=(ubjson_frame&&) = default;
~ubjson_frame() = default;
/// the array or object being written
const BasicJsonType* value;
/// whether value's elements each carry their own type marker; an
/// optimized ($type) container writes it once for all of them instead
bool prefix_required;
typename BasicJsonType::object_t::const_iterator object_it{};
typename BasicJsonType::array_t::const_iterator array_it{};
};
/*!
@@ -1332,11 +1292,11 @@ class binary_writer
bool prefix_required = true;
if (is_array)
{
write_ubjson_start_array(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
write_ubjson_start_container<true>(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
}
else
{
write_ubjson_start_object(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
write_ubjson_start_container<false>(j, use_count, use_type, add_prefix, use_bjdata, prefix_required);
}
const bool empty = is_array ? j.m_data.m_value.array->empty() : j.m_data.m_value.object->empty();
@@ -1346,7 +1306,7 @@ class binary_writer
return;
}
// write_ubjson_start_array/_object return !use_count, i.e. whether a
// write_ubjson_start_container returns !use_count, i.e. whether a
// closer still has to be written; use_count is constant for the whole
// document, so that is recomputed here instead of being carried along
if (!use_count)