Struct FetchObjectWriter 

pub struct FetchObjectWriter {
    group_order: GroupOrder,
    prior_location: Option<(u64, u64)>,
    prior_subgroup_id: Option<u64>,
    prior_publisher_priority: Option<u8>,
}

Re-encodes resolved fetch entries onto one FETCH stream.

The inverse of FetchObjectReader, for a caller writing a different stream from the entries it read: removing an entry changes what the ones after it are encoded against. The entry’s own header is the preference; wherever its shape still encodes the same meaning against the new predecessor it is kept, so a stream with nothing removed is reproduced byte for byte.

CodecError::InvalidField where no encoding exists: a Group ID that moves against the Group Order, an Object ID that does not advance, an Object with neither a Subgroup ID nor the Datagram bit, an End of Group or End of Track whose Object is not the one written before it, and the arithmetic overflows.

Fields

group_order: GroupOrder

prior_location: Option<(u64, u64)>

Group ID and Object ID the next entry is encoded against.

prior_subgroup_id: Option<u64>

Subgroup ID of the last actual Object written that had one.

prior_publisher_priority: Option<u8>

Publisher Priority of the last actual Object written.

Implementations

impl FetchObjectWriter

pub fn new(group_order: GroupOrder) -> Self

A writer for a stream whose Groups are being written in group_order, which has to be the order the FETCH was opened with.

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.

fn range_fields( &self, frame: &FetchObject, ) -> Result<(VarInt, VarInt), CodecError>

An End of Range indicator’s two fields against this predecessor, Section 11.4.2.1.

fn identity_fields( &self, frame: &FetchObject, original: &FetchObjectHeader, ) -> Result<(Option<VarInt>, Option<VarInt>), CodecError>

An Object’s Group ID Delta and Object ID Delta fields against this predecessor, Section 11.4.1.1.

fn subgroup_field( &self, frame: &FetchObject, original: &FetchObjectHeader, ) -> Result<(u64, Option<VarInt>), CodecError>

The Subgroup ID mode bits and the explicit field, if one is needed. The frame’s own mode is tried first.

fn priority_field( &self, frame: &FetchObject, original: &FetchObjectHeader, ) -> Result<Option<u8>, CodecError>

The Publisher Priority field, or None when the predecessor already carries it.

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 writer is left untouched on an error.

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

Record frame as the predecessor of whatever is written next.

Trait Implementations

impl Clone for FetchObjectWriter

fn clone(&self) -> Self

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.