Struct Destination 

pub struct Destination<'a, T, B> { /* private fields */ }

Available on crate features runtime and component-model and component-model-async only.

Represents the buffer for a host- or guest-initiated stream read.

Implementations

impl<'a, T, B> Destination<'a, T, B>

pub fn reborrow(&mut self) -> Destination<'_, T, B>

Reborrow self so it can be used again later.

pub fn take_buffer(&mut self) -> B

where B: Default,

Take the buffer out of self, leaving a default-initialized one in its place.

This can be useful for reusing the previously-stored buffer’s capacity instead of allocating a fresh one.

pub fn set_buffer(&mut self, buffer: B)

Store the specified buffer in self.

Any items contained in the buffer will be delivered to the reader after the StreamProducer::poll_produce call to which this Destination was passed returns (unless overwritten by another call to set_buffer).

If items are stored via this buffer and written via a DirectDestination view of self, then the items in the buffer will be delivered after the ones written using DirectDestination.

pub fn remaining(&self, store: impl AsContextMut) -> Option<usize>

Return the remaining number of items the current read has capacity to accept, if known.

This will return Some(_) if the reader is a guest; it will return None if the reader is the host.

Note that this can return Some(0). This means that the guest is attempting to perform a zero-length read which typically means that it’s trying to wait for this stream to be ready-to-read but is not actually ready to receive the items yet. The host in this case is allowed to either block waiting for readiness or immediately complete the operation. The guest is expected to handle both cases. Some more discussion about this case can be found in the discussion of “Stream Readiness” in the component-model repo.

impl<'a, B> Destination<'a, u8, B>

pub fn as_direct<D>( self, store: StoreContextMut<'a, D>, capacity: usize, ) -> DirectDestination<'a, D>

Return a DirectDestination view of self.

If the reader is a guest, this will provide direct access to the guest’s read buffer. If the reader is a host, this will provide access to a buffer which will be delivered to the host before any items stored using Destination::set_buffer.

capacity will only be used if the reader is a host, in which case it will update the length of the buffer, possibly zero-initializing the new elements if the new length is larger than the old length.