perf: read header.stamp directly from CDR bytes without deserialization#89
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perf: read header.stamp directly from CDR bytes without deserialization#89
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Replace full message deserialization in extract_header_stamp() with direct CDR byte reads at fixed offsets. All types in kTypesWithHeader have std_msgs/msg/Header as their first field, so stamp.sec (offset 4) and stamp.nanosec (offset 8) can be read via memcpy. This eliminates heap allocation and data copying for every message when --use-header-stamp-as-log-time is enabled. The impact is especially significant for large messages like sensor_msgs/msg/Image, where megabytes of pixel data were previously deserialized just to read 8 bytes of timestamp. Also removes 18 ROS message type includes and template instantiations from header_stamp.cpp, reducing compile time.
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Summary
extract_header_stamp()with direct CDR byte reads at fixed offsets (4-11)kTypesWithHeaderhavestd_msgs/msg/Headeras their first field, sostamp.secandstamp.nanosecare at known CDR offsetsheader_stamp.cppBefore
Every message was fully deserialized to read 8 bytes of timestamp. For
sensor_msgs/msg/Image(multi-MB), this allocated and copied the entire pixel buffer.After
Two
memcpycalls readsecandnanosecdirectly from the serialized buffer. Zero heap allocation, zero data copying.Test plan
colcon build)--use-header-stamp-as-log-timeand verify output timestamps match previous behavior--use-header-stamp-as-log-time(code path not reached)