diff options
Diffstat (limited to 'src/sys/wasi/mod.rs')
| -rw-r--r-- | src/sys/wasi/mod.rs | 370 |
1 files changed, 370 insertions, 0 deletions
diff --git a/src/sys/wasi/mod.rs b/src/sys/wasi/mod.rs new file mode 100644 index 0000000..eeea0f2 --- /dev/null +++ b/src/sys/wasi/mod.rs @@ -0,0 +1,370 @@ +//! # Notes +//! +//! The current implementation is somewhat limited. The `Waker` is not +//! implemented, as at the time of writing there is no way to support to wake-up +//! a thread from calling `poll_oneoff`. +//! +//! Furthermore the (re/de)register functions also don't work while concurrently +//! polling as both registering and polling requires a lock on the +//! `subscriptions`. +//! +//! Finally `Selector::try_clone`, required by `Registry::try_clone`, doesn't +//! work. However this could be implemented by use of an `Arc`. +//! +//! In summary, this only (barely) works using a single thread. + +use std::cmp::min; +use std::io; +#[cfg(all(feature = "net", debug_assertions))] +use std::sync::atomic::{AtomicUsize, Ordering}; +use std::sync::{Arc, Mutex}; +use std::time::Duration; + +#[cfg(feature = "net")] +use crate::{Interest, Token}; + +cfg_net! { + pub(crate) mod tcp { + use std::io; + use std::net::{self, SocketAddr}; + + pub(crate) fn accept(listener: &net::TcpListener) -> io::Result<(net::TcpStream, SocketAddr)> { + let (stream, addr) = listener.accept()?; + stream.set_nonblocking(true)?; + Ok((stream, addr)) + } + } +} + +/// Unique id for use as `SelectorId`. +#[cfg(all(debug_assertions, feature = "net"))] +static NEXT_ID: AtomicUsize = AtomicUsize::new(1); + +pub(crate) struct Selector { + #[cfg(all(debug_assertions, feature = "net"))] + id: usize, + /// Subscriptions (reads events) we're interested in. + subscriptions: Arc<Mutex<Vec<wasi::Subscription>>>, +} + +impl Selector { + pub(crate) fn new() -> io::Result<Selector> { + Ok(Selector { + #[cfg(all(debug_assertions, feature = "net"))] + id: NEXT_ID.fetch_add(1, Ordering::Relaxed), + subscriptions: Arc::new(Mutex::new(Vec::new())), + }) + } + + #[cfg(all(debug_assertions, feature = "net"))] + pub(crate) fn id(&self) -> usize { + self.id + } + + pub(crate) fn select(&self, events: &mut Events, timeout: Option<Duration>) -> io::Result<()> { + events.clear(); + + let mut subscriptions = self.subscriptions.lock().unwrap(); + + // If we want to a use a timeout in the `wasi_poll_oneoff()` function + // we need another subscription to the list. + if let Some(timeout) = timeout { + subscriptions.push(timeout_subscription(timeout)); + } + + // `poll_oneoff` needs the same number of events as subscriptions. + let length = subscriptions.len(); + events.reserve(length); + + debug_assert!(events.capacity() >= length); + #[cfg(debug_assertions)] + if length == 0 { + log::warn!( + "calling mio::Poll::poll with empty subscriptions, this likely not what you want" + ); + } + + let res = unsafe { wasi::poll_oneoff(subscriptions.as_ptr(), events.as_mut_ptr(), length) }; + + // Remove the timeout subscription we possibly added above. + if timeout.is_some() { + let timeout_sub = subscriptions.pop(); + debug_assert_eq!( + timeout_sub.unwrap().u.tag, + wasi::EVENTTYPE_CLOCK.raw(), + "failed to remove timeout subscription" + ); + } + + drop(subscriptions); // Unlock. + + match res { + Ok(n_events) => { + // Safety: `poll_oneoff` initialises the `events` for us. + unsafe { events.set_len(n_events) }; + + // Remove the timeout event. + if timeout.is_some() { + if let Some(index) = events.iter().position(is_timeout_event) { + events.swap_remove(index); + } + } + + check_errors(&events) + } + Err(err) => Err(io_err(err)), + } + } + + pub(crate) fn try_clone(&self) -> io::Result<Selector> { + Ok(Selector { + #[cfg(all(debug_assertions, feature = "net"))] + id: self.id, + subscriptions: self.subscriptions.clone(), + }) + } + + #[cfg(feature = "net")] + pub(crate) fn register( + &self, + fd: wasi::Fd, + token: Token, + interests: Interest, + ) -> io::Result<()> { + let mut subscriptions = self.subscriptions.lock().unwrap(); + + if interests.is_writable() { + let subscription = wasi::Subscription { + userdata: token.0 as wasi::Userdata, + u: wasi::SubscriptionU { + tag: wasi::EVENTTYPE_FD_WRITE.raw(), + u: wasi::SubscriptionUU { + fd_write: wasi::SubscriptionFdReadwrite { + file_descriptor: fd, + }, + }, + }, + }; + subscriptions.push(subscription); + } + + if interests.is_readable() { + let subscription = wasi::Subscription { + userdata: token.0 as wasi::Userdata, + u: wasi::SubscriptionU { + tag: wasi::EVENTTYPE_FD_READ.raw(), + u: wasi::SubscriptionUU { + fd_read: wasi::SubscriptionFdReadwrite { + file_descriptor: fd, + }, + }, + }, + }; + subscriptions.push(subscription); + } + + Ok(()) + } + + #[cfg(feature = "net")] + pub(crate) fn reregister( + &self, + fd: wasi::Fd, + token: Token, + interests: Interest, + ) -> io::Result<()> { + self.deregister(fd) + .and_then(|()| self.register(fd, token, interests)) + } + + #[cfg(feature = "net")] + pub(crate) fn deregister(&self, fd: wasi::Fd) -> io::Result<()> { + let mut subscriptions = self.subscriptions.lock().unwrap(); + + let predicate = |subscription: &wasi::Subscription| { + // Safety: `subscription.u.tag` defines the type of the union in + // `subscription.u.u`. + match subscription.u.tag { + t if t == wasi::EVENTTYPE_FD_WRITE.raw() => unsafe { + subscription.u.u.fd_write.file_descriptor == fd + }, + t if t == wasi::EVENTTYPE_FD_READ.raw() => unsafe { + subscription.u.u.fd_read.file_descriptor == fd + }, + _ => false, + } + }; + + let mut ret = Err(io::ErrorKind::NotFound.into()); + + while let Some(index) = subscriptions.iter().position(predicate) { + subscriptions.swap_remove(index); + ret = Ok(()) + } + + ret + } +} + +/// Token used to a add a timeout subscription, also used in removing it again. +const TIMEOUT_TOKEN: wasi::Userdata = wasi::Userdata::max_value(); + +/// Returns a `wasi::Subscription` for `timeout`. +fn timeout_subscription(timeout: Duration) -> wasi::Subscription { + wasi::Subscription { + userdata: TIMEOUT_TOKEN, + u: wasi::SubscriptionU { + tag: wasi::EVENTTYPE_CLOCK.raw(), + u: wasi::SubscriptionUU { + clock: wasi::SubscriptionClock { + id: wasi::CLOCKID_MONOTONIC, + // Timestamp is in nanoseconds. + timeout: min(wasi::Timestamp::MAX as u128, timeout.as_nanos()) + as wasi::Timestamp, + // Give the implementation another millisecond to coalesce + // events. + precision: Duration::from_millis(1).as_nanos() as wasi::Timestamp, + // Zero means the `timeout` is considered relative to the + // current time. + flags: 0, + }, + }, + }, + } +} + +fn is_timeout_event(event: &wasi::Event) -> bool { + event.type_ == wasi::EVENTTYPE_CLOCK && event.userdata == TIMEOUT_TOKEN +} + +/// Check all events for possible errors, it returns the first error found. +fn check_errors(events: &[Event]) -> io::Result<()> { + for event in events { + if event.error != wasi::ERRNO_SUCCESS { + return Err(io_err(event.error)); + } + } + Ok(()) +} + +/// Convert `wasi::Errno` into an `io::Error`. +fn io_err(errno: wasi::Errno) -> io::Error { + // TODO: check if this is valid. + io::Error::from_raw_os_error(errno.raw() as i32) +} + +pub(crate) type Events = Vec<Event>; + +pub(crate) type Event = wasi::Event; + +pub(crate) mod event { + use std::fmt; + + use crate::sys::Event; + use crate::Token; + + pub(crate) fn token(event: &Event) -> Token { + Token(event.userdata as usize) + } + + pub(crate) fn is_readable(event: &Event) -> bool { + event.type_ == wasi::EVENTTYPE_FD_READ + } + + pub(crate) fn is_writable(event: &Event) -> bool { + event.type_ == wasi::EVENTTYPE_FD_WRITE + } + + pub(crate) fn is_error(_: &Event) -> bool { + // Not supported? It could be that `wasi::Event.error` could be used for + // this, but the docs say `error that occurred while processing the + // subscription request`, so it's checked in `Select::select` already. + false + } + + pub(crate) fn is_read_closed(event: &Event) -> bool { + event.type_ == wasi::EVENTTYPE_FD_READ + // Safety: checked the type of the union above. + && (event.fd_readwrite.flags & wasi::EVENTRWFLAGS_FD_READWRITE_HANGUP) != 0 + } + + pub(crate) fn is_write_closed(event: &Event) -> bool { + event.type_ == wasi::EVENTTYPE_FD_WRITE + // Safety: checked the type of the union above. + && (event.fd_readwrite.flags & wasi::EVENTRWFLAGS_FD_READWRITE_HANGUP) != 0 + } + + pub(crate) fn is_priority(_: &Event) -> bool { + // Not supported. + false + } + + pub(crate) fn is_aio(_: &Event) -> bool { + // Not supported. + false + } + + pub(crate) fn is_lio(_: &Event) -> bool { + // Not supported. + false + } + + pub(crate) fn debug_details(f: &mut fmt::Formatter<'_>, event: &Event) -> fmt::Result { + debug_detail!( + TypeDetails(wasi::Eventtype), + PartialEq::eq, + wasi::EVENTTYPE_CLOCK, + wasi::EVENTTYPE_FD_READ, + wasi::EVENTTYPE_FD_WRITE, + ); + + #[allow(clippy::trivially_copy_pass_by_ref)] + fn check_flag(got: &wasi::Eventrwflags, want: &wasi::Eventrwflags) -> bool { + (got & want) != 0 + } + debug_detail!( + EventrwflagsDetails(wasi::Eventrwflags), + check_flag, + wasi::EVENTRWFLAGS_FD_READWRITE_HANGUP, + ); + + struct EventFdReadwriteDetails(wasi::EventFdReadwrite); + + impl fmt::Debug for EventFdReadwriteDetails { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("EventFdReadwrite") + .field("nbytes", &self.0.nbytes) + .field("flags", &self.0.flags) + .finish() + } + } + + f.debug_struct("Event") + .field("userdata", &event.userdata) + .field("error", &event.error) + .field("type", &TypeDetails(event.type_)) + .field("fd_readwrite", &EventFdReadwriteDetails(event.fd_readwrite)) + .finish() + } +} + +cfg_os_poll! { + cfg_io_source! { + pub(crate) struct IoSourceState; + + impl IoSourceState { + pub(crate) fn new() -> IoSourceState { + IoSourceState + } + + pub(crate) fn do_io<T, F, R>(&self, f: F, io: &T) -> io::Result<R> + where + F: FnOnce(&T) -> io::Result<R>, + { + // We don't hold state, so we can just call the function and + // return. + f(io) + } + } + } +} |