Struct hyper::ffi::hyper_waker
source · pub struct hyper_waker { /* private fields */ }
ffi
and hyper_unstable_ffi
only.Expand description
A waker that is saved and used to waken a pending task.
This is provided to hyper_io
’s read and write callbacks via hyper_context
and hyper_context_waker
.
When nonblocking I/O in one of those callbacks can’t make progress (returns
EAGAIN
or EWOULDBLOCK
), the callback has to return to avoid blocking the
executor. But it also has to arrange to get called in the future when more
data is available. That’s the role of the async context and the waker. The
waker can be used to tell the executor “this task is ready to make progress.”
The read or write callback, upon finding it can’t make progress, must get a
waker from the context (hyper_context_waker
), arrange for that waker to be
called in the future, and then return HYPER_POLL_PENDING
.
The arrangements for the waker to be called in the future are up to the
application, but usually it will involve one big select(2)
loop that checks which
FDs are ready, and a correspondence between FDs and waker objects. For each
FD that is ready, the corresponding waker must be called. Then hyper_executor_poll
must be called. That will cause the executor to attempt to make progress on each
woken task.
Corresponding Rust type: https://doc.rust-lang.org/std/task/struct.Waker.html