Struct SubgroupHeader

Source

pub struct SubgroupHeader {
    pub stream_type: SubgroupStreamType,
    pub track_alias: VarInt,
    pub group_id: VarInt,
    pub subgroup_id: Option<VarInt>,
    pub publisher_priority: u8,
}

Expand description

Subgroup stream header.

Wire order: type byte, Track Alias, Group ID, Subgroup ID (only for stream types that carry one), Publisher Priority.

Fields§

§stream_type: SubgroupStreamType

Type byte identifying the flag set for this stream.

§track_alias: VarInt

Track alias.

§group_id: VarInt

Group ID.

§subgroup_id: Option<VarInt>

Explicit Subgroup ID — present only when the stream type sets Subgroup ID Field Present = Yes. For types where the subgroup ID is implicit (0 or the first Object ID), the effective subgroup ID is resolved on the receive side by the reader.

§publisher_priority: u8

Publisher priority.

Implementations§

Source §

impl SubgroupHeader

Source

pub fn encode(&self, buf: &mut impl BufMut)

Encode the header including the leading stream type byte.

Driven by stream_type, and silent about a subgroup_id that disagrees with it in either direction: a None under a type whose Subgroup ID Field Present column reads Yes is written as zero, which names a different subgroup rather than no subgroup, and a Some under a type whose column reads No is dropped. Both write a well-formed stream describing something other than what the caller built. Self::encode_checked refuses that shape instead.

Source

pub fn encode_checked(&self, buf: &mut impl BufMut) -> Result<(), CodecError>

Encode, refusing a header whose Subgroup ID disagrees with its own type byte.

Section 10.4.2 gives the SUBGROUP_HEADER type table a Subgroup ID Field Present column, and that column - not the value in hand - decides whether the field is on the wire. Self::decode therefore only ever produces a header where the two agree, so this refuses exactly the shapes a caller assembled by hand: an absent ID under a type that carries one, and a present ID under a type that does not.

Nothing about the value is refused. Zero is a legal Subgroup ID, so a Some(0) under a type that carries the field is written as the caller asked.

§Errors

CodecError::InvalidField if the presence of subgroup_id does not match what stream_type puts on the wire.

Source

pub fn decode(buf: &mut impl Buf) -> Result<Self, CodecError>

Decode a subgroup header (leading type byte + remaining fields).

Errors with CodecError::UnknownStreamType when the stream table does not assign the leading type, which this draft answers with a close, and with CodecError::InvalidField for 0x05, which it assigns to a fetch stream. stream_type_error draws that line.