rmw_mut_byte_span_t Struct Reference

#include <rmw_entity.h>

Data Fields
size_t	capacity
uint8_t *	data
size_t	len

Detailed Description

Room to WRITE — phase-406 W2.

This is upstream's rmw_serialized_message_t MINUS THE ALLOCATOR. That is not a coincidence and it is the whole argument: upstream's is an rcutils_uint8_array_t, {buffer, buffer_length, buffer_capacity, allocator}, and this ABI declined it because of the last field. Drop that field and the remaining three are exactly what a caller-owned destination needs, so the "carries an allocator" objection does not transfer to this.

capacity is a LIMIT (in) and len is a RESULT (out). They are separate fields rather than one overloaded len because "capacity on the way in, length on the way out" is the snprintf ambiguity, and it is a bug generator.

PASSED BY POINTER, always. The callee must set len, and a by-value copy would discard it — code that compiles, runs, and yields zero-length messages.

Field Documentation

capacity

size_t rmw_mut_byte_span_t::capacity

In: bytes available at data.

data

uint8_t* rmw_mut_byte_span_t::data

len

size_t rmw_mut_byte_span_t::len

Out: bytes actually written. Undefined on failure.

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The documentation for this struct was generated from the following file:

• include/nros/rmw_entity.h