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Reuse FastBuffer managed buffer for each endpoint. #904

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Reuse FastBuffer managed buffer for each endpoint. #904

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18 changes: 12 additions & 6 deletions rmw_fastrtps_cpp/src/rmw_publish.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -171,13 +171,19 @@ publish_to_buffer_endpoints(
}

// Publish to per-subscriber peer-to-peer endpoints for non-CPU subscribers.
for (const auto & endpoint : state.endpoints) {
uint32_t serialized_size = callbacks->get_serialized_size(ros_message);
size_t buffer_size = serialized_size + 4; // +4 for CDR encapsulation header
std::vector<uint8_t> buffer_data(buffer_size);

eprosima::fastcdr::FastBuffer fast_buffer(
reinterpret_cast<char *>(buffer_data.data()), buffer_size);
// Intentionally reuse an internally managed FastBuffer across endpoints. Each Cdr
// starts at the beginning and owns its cursor, and `write_w_timestamp()` copies
// the data before returning, so reuse is safe.
//
// Preallocating with `get_serialized_size()` is not recommended: for
// `rosidl::Buffer`, it may report the full CPU fallback size even when only a
// small descriptor is sent.
//
// The buffer grows automatically and lazily without zero-initialization.
eprosima::fastcdr::FastBuffer fast_buffer;

for (const auto & endpoint : state.endpoints) {
eprosima::fastcdr::Cdr ser(
fast_buffer, eprosima::fastcdr::Cdr::DEFAULT_ENDIAN,
eprosima::fastcdr::CdrVersion::XCDRv1);
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