Struct FetchObjectWriter 

pub struct FetchObjectWriter { /* private fields */ }

Re-encodes resolved fetch frames onto one FETCH stream.

The exact inverse of FetchObjectReader, and it exists for one caller: something that has read a stream and is writing a different stream from the same frames. Removing a frame changes what the frames after it are read against, and draft-17 Section 10.4.4.1 lets an Object leave out its Group ID, Object ID, Subgroup ID and Priority and take the prior Object’s, so the survivor that follows a removed run cannot keep its original bytes: a field it left off has to appear, and a flag bit with it.

Draft-17 states these fields, it does not delta them

A Group ID or Object ID that is on the wire here is the absolute value, not a difference — the deltas arrive at draft-18. What is stateful is the omission: no Group ID means the prior Object’s, and no Object ID means the prior Object’s plus one. That is enough to make removal a re-encode, and it is why this writer refuses nothing an Object can be: every identity has an encoding here, however the predecessor moved.

Why this is not a general encoder

Every frame it writes came off a stream, so the caller holds the frame’s own FetchObjectHeader alongside the resolved values, and that header is used as the preference: wherever the original shape still says the same thing against the new predecessor it is kept, so a stream with nothing removed is reproduced byte for byte.

Implementations

impl FetchObjectWriter

pub fn new() -> Self

A writer positioned before the first Object of a fetch stream, with no prior Object for anything to be encoded against.

pub fn header_for( &self, frame: &FetchObject, ) -> Result<FetchObjectHeader, CodecError>

The header that encodes frame against everything written so far.

Does not advance the writer — Self::write_object_header is the call that does both.

Errors

CodecError::InvalidField for an Object with neither a Subgroup ID nor the Datagram bit, and for one with no Priority: both are frames no draft-17 stream could carry, and inventing a value would put a different Object on the wire than the one this was handed.

pub fn write_object_header( &mut self, frame: &FetchObject, out: &mut impl BufMut, ) -> Result<FetchObjectHeader, CodecError>

Encode frame against everything written so far and advance.

Writes the header only. The payload is frame.header.payload_length bytes and is the caller’s to copy, unchanged.

Errors

CodecError::InvalidField for a frame with no encoding at all; the writer is left untouched when this happens.

pub fn advance(&mut self, frame: &FetchObject)

Record frame as the predecessor of whatever is written next.

Public because a re-emitting caller has a second way of putting a frame on the wire: when the framing it arrived in still encodes the same meaning against the frame before it, its own bytes are forwarded untouched — no header is produced and nothing is copied. The writer still has to move, or the frame after it is encoded against a predecessor one frame stale.

Trait Implementations

impl Clone for FetchObjectWriter

fn clone(&self) -> FetchObjectWriter

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FetchObjectWriter

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

Formats the value using the given formatter.

impl Default for FetchObjectWriter

fn default() -> FetchObjectWriter

Returns the “default value” for a type.