Rename poll-list to poll, poll-one to pollable.block, and introduce pollable.ready #7427
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added 8 commits
October 31, 2023 10:14
* move contents of Host::poll_one to HostPollable::block * rename Host::poll_list to Host::poll, * implement HostPollable::ready, using futures::future::poll_immediate
this is an optimization, but what it really allows us to do is assert pollable.ready() for a subscribe_duration(0) is ready immediately.
test-programs/src/bin/preview2_sleep.rs in particular now asserts ready() on a subscribe_duration(0) and a subscribe_instant(now() - 1), so we have test coverage for ready as well now
alexcrichton
approved these changes
Oct 31, 2023
| "poll-one", | ||
| "poll", | ||
| "[method]pollable.block", | ||
| "[method]pollable.ready", |
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Ideally this method wouldn't be on this list since it shouldn't block, but I can also see how that complicates the implementation, so I'm fine either way
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Agreed. The implementation, as it stands, shouldn't ever actually be Pending, and I think we will be able to keep an eye on that invariant going forwards.
crates/wasi/src/preview2/poll.rs
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| let pollable = table.get(&pollable)?; | ||
| let ready = (pollable.make_future)(table.get_any_mut(pollable.index)?); | ||
| futures::pin_mut!(ready); | ||
| Ok(futures::future::poll_immediate(ready).await.is_some()) |
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Could this perhaps be matches!(..., Some(())) to emphasize this isn't accidentally throwing away a "real" result from the poll?
Co-authored-by: Alex Crichton <alex@alexcrichton.com>
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Downstreaming changes to wasi:io/poll proposed here:
WebAssembly/wasi-io#54
poll-list becomes poll and poll-one becomes a method directly on pollable - these are NFCs, just renamings for ergonomics, and because poll-one was easily confused with poll-oneoff.
pollable.ready is new functionality that allows you to check the readiness of a pollable without blocking. I took the most trivial path to implement it via futures::poll_immediate. I had to add a minor optimization to the clock deadline future so that we can test it by asserting
subscribe_duration(0).ready()andsubscribe_instant(now() - 1).ready()are true.