Struct rmw_mut_byte_span_t 

#[repr(C)]
pub struct rmw_mut_byte_span_t {
    pub data: *mut u8,
    pub capacity: usize,
    pub len: usize,
}

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.

Fields

data: *mut u8

capacity: usize

In: bytes available at data.

len: usize

Out: bytes actually written.

On NROS_RMW_RET_BUFFER_TOO_SMALL from any of the three TAKE slots — the subscription take (issue 1612), the service take_request and the client take_response (issue 1632) — it is the size the refused sample, request or reply NEEDED, or NROS_RMW_TAKE_LEN_UNKNOWN when the backend cannot know it. The caller pre-sets it to that value on all three. Undefined on every other failure.

Trait Implementations

impl Clone for rmw_mut_byte_span_t

fn clone(&self) -> rmw_mut_byte_span_t

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for rmw_mut_byte_span_t

impl Debug for rmw_mut_byte_span_t

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.