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use crate::io::interest::Interest;
use crate::runtime::io::Registration;
use crate::runtime::scheduler;
use mio::event::Source;
use std::fmt;
use std::io;
use std::ops::Deref;
use std::panic::{RefUnwindSafe, UnwindSafe};
cfg_io_driver! {
/// Associates an I/O resource that implements the [`std::io::Read`] and/or
/// [`std::io::Write`] traits with the reactor that drives it.
///
/// `PollEvented` uses [`Registration`] internally to take a type that
/// implements [`mio::event::Source`] as well as [`std::io::Read`] and/or
/// [`std::io::Write`] and associate it with a reactor that will drive it.
///
/// Once the [`mio::event::Source`] type is wrapped by `PollEvented`, it can be
/// used from within the future's execution model. As such, the
/// `PollEvented` type provides [`AsyncRead`] and [`AsyncWrite`]
/// implementations using the underlying I/O resource as well as readiness
/// events provided by the reactor.
///
/// **Note**: While `PollEvented` is `Sync` (if the underlying I/O type is
/// `Sync`), the caller must ensure that there are at most two tasks that
/// use a `PollEvented` instance concurrently. One for reading and one for
/// writing. While violating this requirement is "safe" from a Rust memory
/// model point of view, it will result in unexpected behavior in the form
/// of lost notifications and tasks hanging.
///
/// ## Readiness events
///
/// Besides just providing [`AsyncRead`] and [`AsyncWrite`] implementations,
/// this type also supports access to the underlying readiness event stream.
/// While similar in function to what [`Registration`] provides, the
/// semantics are a bit different.
///
/// Two functions are provided to access the readiness events:
/// [`poll_read_ready`] and [`poll_write_ready`]. These functions return the
/// current readiness state of the `PollEvented` instance. If
/// [`poll_read_ready`] indicates read readiness, immediately calling
/// [`poll_read_ready`] again will also indicate read readiness.
///
/// When the operation is attempted and is unable to succeed due to the I/O
/// resource not being ready, the caller must call [`clear_readiness`].
/// This clears the readiness state until a new readiness event is received.
///
/// This allows the caller to implement additional functions. For example,
/// [`TcpListener`] implements poll_accept by using [`poll_read_ready`] and
/// [`clear_readiness`].
///
/// ## Platform-specific events
///
/// `PollEvented` also allows receiving platform-specific `mio::Ready` events.
/// These events are included as part of the read readiness event stream. The
/// write readiness event stream is only for `Ready::writable()` events.
///
/// [`AsyncRead`]: crate::io::AsyncRead
/// [`AsyncWrite`]: crate::io::AsyncWrite
/// [`TcpListener`]: crate::net::TcpListener
/// [`clear_readiness`]: Registration::clear_readiness
/// [`poll_read_ready`]: Registration::poll_read_ready
/// [`poll_write_ready`]: Registration::poll_write_ready
pub(crate) struct PollEvented<E: Source> {
io: Option<E>,
registration: Registration,
}
}
// ===== impl PollEvented =====
impl<E: Source> PollEvented<E> {
/// Creates a new `PollEvented` associated with the default reactor.
///
/// The returned `PollEvented` has readable and writable interests. For more control, use
/// [`Self::new_with_interest`].
///
/// # Panics
///
/// This function panics if thread-local runtime is not set.
///
/// The runtime is usually set implicitly when this function is called
/// from a future driven by a tokio runtime, otherwise runtime can be set
/// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
#[track_caller]
#[cfg_attr(feature = "signal", allow(unused))]
pub(crate) fn new(io: E) -> io::Result<Self> {
PollEvented::new_with_interest(io, Interest::READABLE | Interest::WRITABLE)
}
/// Creates a new `PollEvented` associated with the default reactor, for
/// specific `Interest` state. `new_with_interest` should be used over `new`
/// when you need control over the readiness state, such as when a file
/// descriptor only allows reads. This does not add `hup` or `error` so if
/// you are interested in those states, you will need to add them to the
/// readiness state passed to this function.
///
/// # Panics
///
/// This function panics if thread-local runtime is not set.
///
/// The runtime is usually set implicitly when this function is called from
/// a future driven by a tokio runtime, otherwise runtime can be set
/// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter)
/// function.
#[track_caller]
#[cfg_attr(feature = "signal", allow(unused))]
pub(crate) fn new_with_interest(io: E, interest: Interest) -> io::Result<Self> {
Self::new_with_interest_and_handle(io, interest, scheduler::Handle::current())
}
#[track_caller]
pub(crate) fn new_with_interest_and_handle(
mut io: E,
interest: Interest,
handle: scheduler::Handle,
) -> io::Result<Self> {
let registration = Registration::new_with_interest_and_handle(&mut io, interest, handle)?;
Ok(Self {
io: Some(io),
registration,
})
}
/// Returns a reference to the registration.
#[cfg(any(feature = "net"))]
pub(crate) fn registration(&self) -> &Registration {
&self.registration
}
/// Deregisters the inner io from the registration and returns a Result containing the inner io.
#[cfg(any(feature = "net", feature = "process"))]
pub(crate) fn into_inner(mut self) -> io::Result<E> {
let mut inner = self.io.take().unwrap(); // As io shouldn't ever be None, just unwrap here.
self.registration.deregister(&mut inner)?;
Ok(inner)
}
}
feature! {
#![any(feature = "net", all(unix, feature = "process"))]
use crate::io::ReadBuf;
use std::task::{Context, Poll};
impl<E: Source> PollEvented<E> {
// Safety: The caller must ensure that `E` can read into uninitialized memory
pub(crate) unsafe fn poll_read<'a>(
&'a self,
cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>>
where
&'a E: io::Read + 'a,
{
use std::io::Read;
loop {
let evt = ready!(self.registration.poll_read_ready(cx))?;
let b = &mut *(buf.unfilled_mut() as *mut [std::mem::MaybeUninit<u8>] as *mut [u8]);
let len = b.len();
match self.io.as_ref().unwrap().read(b) {
Ok(n) => {
// if we read a partially full buffer, this is sufficient on unix to show
// that the socket buffer has been drained
if n > 0 && (!cfg!(windows) && n < len) {
self.registration.clear_readiness(evt);
}
// Safety: We trust `TcpStream::read` to have filled up `n` bytes in the
// buffer.
buf.assume_init(n);
buf.advance(n);
return Poll::Ready(Ok(()));
},
Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
self.registration.clear_readiness(evt);
}
Err(e) => return Poll::Ready(Err(e)),
}
}
}
pub(crate) fn poll_write<'a>(&'a self, cx: &mut Context<'_>, buf: &[u8]) -> Poll<io::Result<usize>>
where
&'a E: io::Write + 'a,
{
use std::io::Write;
loop {
let evt = ready!(self.registration.poll_write_ready(cx))?;
match self.io.as_ref().unwrap().write(buf) {
Ok(n) => {
// if we write only part of our buffer, this is sufficient on unix to show
// that the socket buffer is full
if n > 0 && (!cfg!(windows) && n < buf.len()) {
self.registration.clear_readiness(evt);
}
return Poll::Ready(Ok(n));
},
Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
self.registration.clear_readiness(evt);
}
Err(e) => return Poll::Ready(Err(e)),
}
}
}
#[cfg(any(feature = "net", feature = "process"))]
pub(crate) fn poll_write_vectored<'a>(
&'a self,
cx: &mut Context<'_>,
bufs: &[io::IoSlice<'_>],
) -> Poll<io::Result<usize>>
where
&'a E: io::Write + 'a,
{
use std::io::Write;
self.registration.poll_write_io(cx, || self.io.as_ref().unwrap().write_vectored(bufs))
}
}
}
impl<E: Source> UnwindSafe for PollEvented<E> {}
impl<E: Source> RefUnwindSafe for PollEvented<E> {}
impl<E: Source> Deref for PollEvented<E> {
type Target = E;
fn deref(&self) -> &E {
self.io.as_ref().unwrap()
}
}
impl<E: Source + fmt::Debug> fmt::Debug for PollEvented<E> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("PollEvented").field("io", &self.io).finish()
}
}
impl<E: Source> Drop for PollEvented<E> {
fn drop(&mut self) {
if let Some(mut io) = self.io.take() {
// Ignore errors
let _ = self.registration.deregister(&mut io);
}
}
}