Struct PacketHeader

pub struct PacketHeader {
    pub buffer_lifetime_ordinal: Option<u64>,
    pub packet_index: Option<u32>,
    /* private fields */
}

PacketHeader

When referring to a free packet, we use PacketHeader alone instead of Packet, since while a packet is free it doesn’t really have meaningful offset or length etc.

A populated Packet also has a PacketHeader.

Fields

buffer_lifetime_ordinal: Option<u64>

This is which buffer configuration lifetime this header is referring to.

A packet_index is only really meaningful with respect to a particular buffer_lifetime_ordinal.

See StreamBufferPartialSettings.buffer_lifetime_ordinal.

For QueueInputPacket(), a server receiving a buffer_lifetime_ordinal that isn’t the current input buffer_lifetime_ordinal will close the channel.

For OnFreeInputPacket() and RecycleOutputPacket(), the receiver (client or server) must ignore a message with stale buffer_lifetime_ordinal.

packet_index: Option<u32>

The overall set of packet_index values is densely packed from 0..count-1 for input and output separately. They can be queued in any order.

Both the client and server should validate the packet_index against the known bound and disconnect if it’s out of bounds.

When running in single-buffer mode, the buffer index is always 0.

The packet_index values don’t imply anything about order of use of packets. The client should not expect the ordering to remain the same over time - the stream processor is free to hold on to an input or output packet for a while during which other packet_index values may be used multiple times.

For a given properly-functioning StreamProcessor instance, packet_index values will be unique among concurrently-outstanding packets. Servers should validate that a client isn’t double-using a packet and clients should validate as necessary to avoid undefined or unexpected client behavior.

Trait Implementations

impl Clone for PacketHeader

fn clone(&self) -> PacketHeader

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for PacketHeader

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

Formats the value using the given formatter.

impl<D: ResourceDialect> Decode<PacketHeader, D> for PacketHeader

fn new_empty() -> Self

Creates a valid instance of Self. The specific value does not matter, since it will be overwritten by decode.

unsafe fn decode( &mut self, decoder: &mut Decoder<'_, D>, offset: usize, depth: Depth, ) -> Result<()>

Decodes an object of type T from the decoder’s buffers into self.

impl Default for PacketHeader

fn default() -> PacketHeader

Returns the “default value” for a type.

impl<D: ResourceDialect> Encode<PacketHeader, D> for &PacketHeader

unsafe fn encode( self, encoder: &mut Encoder<'_, D>, offset: usize, depth: Depth, ) -> Result<()>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID.

impl PartialEq for PacketHeader

fn eq(&self, other: &PacketHeader) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl TypeMarker for PacketHeader

type Owned = PacketHeader

The owned Rust type which this FIDL type decodes into.

fn inline_align(_context: Context) -> usize

Returns the minimum required alignment of the inline portion of the encoded object. It must be a (nonzero) power of two.

fn inline_size(_context: Context) -> usize

Returns the size of the inline portion of the encoded object, including padding for alignment. Must be a multiple of inline_align.

fn encode_is_copy() -> bool

Returns true if the memory layout of Self::Owned matches the FIDL wire format and encoding requires no validation. When true, we can optimize encoding arrays and vectors of Self::Owned to a single memcpy.

fn decode_is_copy() -> bool

Returns true if the memory layout of Self::Owned matches the FIDL wire format and decoding requires no validation. When true, we can optimize decoding arrays and vectors of Self::Owned to a single memcpy.

impl ValueTypeMarker for PacketHeader

type Borrowed<'a> = &'a PacketHeader

The Rust type to use for encoding. This is a particular Encode<Self> type cheaply obtainable from &Self::Owned. There are three cases:

fn borrow(value: &<Self as TypeMarker>::Owned) -> Self::Borrowed<'_>

Cheaply converts from &Self::Owned to Self::Borrowed.

impl Persistable for PacketHeader

impl StructuralPartialEq for PacketHeader