calloop/sources/generic.rs
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//! A generic event source wrapping an IO objects or file descriptor
//!
//! You can use this general purpose adapter around file-descriptor backed objects to
//! insert into an [`EventLoop`](crate::EventLoop).
//!
//! The event generated by this [`Generic`] event source are the [`Readiness`](crate::Readiness)
//! notification itself, and the monitored object is provided to your callback as the second
//! argument.
//!
#![cfg_attr(unix, doc = "```")]
#![cfg_attr(not(unix), doc = "```no_run")]
//! # extern crate calloop;
//! use calloop::{generic::Generic, Interest, Mode, PostAction};
//!
//! # fn main() {
//! # let mut event_loop = calloop::EventLoop::<()>::try_new()
//! # .expect("Failed to initialize the event loop!");
//! # let handle = event_loop.handle();
//! # #[cfg(unix)]
//! # let io_object = std::io::stdin();
//! # #[cfg(windows)]
//! # let io_object: std::net::TcpStream = panic!();
//! handle.insert_source(
//! // wrap your IO object in a Generic, here we register for read readiness
//! // in level-triggering mode
//! Generic::new(io_object, Interest::READ, Mode::Level),
//! |readiness, io_object, shared_data| {
//! // The first argument of the callback is a Readiness
//! // The second is a &mut reference to your object
//!
//! // your callback needs to return a Result<PostAction, std::io::Error>
//! // if it returns an error, the event loop will consider this event
//! // event source as erroring and report it to the user.
//! Ok(PostAction::Continue)
//! }
//! );
//! # }
//! ```
//!
//! It can also help you implementing your own event sources: just have
//! these `Generic<_>` as fields of your event source, and delegate the
//! [`EventSource`](crate::EventSource) implementation to them.
use polling::Poller;
use std::{borrow, marker::PhantomData, ops, sync::Arc};
#[cfg(unix)]
use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd};
#[cfg(windows)]
use std::os::windows::io::{
AsRawSocket as AsRawFd, AsSocket as AsFd, BorrowedSocket as BorrowedFd,
};
use crate::{EventSource, Interest, Mode, Poll, PostAction, Readiness, Token, TokenFactory};
/// Wrapper to use a type implementing `AsRawFd` but not `AsFd` with `Generic`
#[derive(Debug)]
pub struct FdWrapper<T: AsRawFd>(T);
impl<T: AsRawFd> FdWrapper<T> {
/// Wrap `inner` with an `AsFd` implementation.
///
/// # Safety
/// This is safe if the `AsRawFd` implementation of `inner` always returns
/// a valid fd. This should usually be true for types implementing
/// `AsRawFd`. But this isn't guaranteed with `FdWrapper<RawFd>`.
pub unsafe fn new(inner: T) -> Self {
Self(inner)
}
}
impl<T: AsRawFd> ops::Deref for FdWrapper<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl<T: AsRawFd> ops::DerefMut for FdWrapper<T> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.0
}
}
impl<T: AsRawFd> AsFd for FdWrapper<T> {
#[cfg(unix)]
fn as_fd(&self) -> BorrowedFd {
unsafe { BorrowedFd::borrow_raw(self.0.as_raw_fd()) }
}
#[cfg(windows)]
fn as_socket(&self) -> BorrowedFd {
unsafe { BorrowedFd::borrow_raw(self.0.as_raw_socket()) }
}
}
/// A wrapper around a type that doesn't expose it mutably safely.
///
/// The [`EventSource`] trait's `Metadata` type demands mutable access to the inner I/O source.
/// However, the inner polling source used by `calloop` keeps the handle-based equivalent of an
/// immutable pointer to the underlying object's I/O handle. Therefore, if the inner source is
/// dropped, this leaves behind a dangling pointer which immediately invokes undefined behavior
/// on the next poll of the event loop.
///
/// In order to prevent this from happening, the [`Generic`] I/O source must not directly expose
/// a mutable reference to the underlying handle. This type wraps around the underlying handle and
/// easily allows users to take immutable (`&`) references to the type, but makes mutable (`&mut`)
/// references unsafe to get. Therefore, it prevents the source from being moved out and dropped
/// while it is still registered in the event loop.
///
/// [`EventSource`]: crate::EventSource
#[derive(Debug)]
pub struct NoIoDrop<T>(T);
impl<T> NoIoDrop<T> {
/// Get a mutable reference.
///
/// # Safety
///
/// The inner type's I/O source must not be dropped.
pub unsafe fn get_mut(&mut self) -> &mut T {
&mut self.0
}
}
impl<T> AsRef<T> for NoIoDrop<T> {
fn as_ref(&self) -> &T {
&self.0
}
}
impl<T> borrow::Borrow<T> for NoIoDrop<T> {
fn borrow(&self) -> &T {
&self.0
}
}
impl<T> ops::Deref for NoIoDrop<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl<T: AsFd> AsFd for NoIoDrop<T> {
#[cfg(unix)]
fn as_fd(&self) -> BorrowedFd<'_> {
// SAFETY: The innter type is not mutated.
self.0.as_fd()
}
#[cfg(windows)]
fn as_socket(&self) -> BorrowedFd<'_> {
// SAFETY: The innter type is not mutated.
self.0.as_socket()
}
}
/// A generic event source wrapping a FD-backed type
#[derive(Debug)]
pub struct Generic<F: AsFd, E = std::io::Error> {
/// The wrapped FD-backed type.
///
/// This must be deregistered before it is dropped.
file: Option<NoIoDrop<F>>,
/// The programmed interest
pub interest: Interest,
/// The programmed mode
pub mode: Mode,
/// Back-reference to the poller.
///
/// This is needed to drop the original file.
poller: Option<Arc<Poller>>,
// This token is used by the event loop logic to look up this source when an
// event occurs.
token: Option<Token>,
// This allows us to make the associated error and return types generic.
_error_type: PhantomData<E>,
}
impl<F: AsFd> Generic<F, std::io::Error> {
/// Wrap a FD-backed type into a `Generic` event source that uses
/// [`std::io::Error`] as its error type.
pub fn new(file: F, interest: Interest, mode: Mode) -> Generic<F, std::io::Error> {
Generic {
file: Some(NoIoDrop(file)),
interest,
mode,
token: None,
poller: None,
_error_type: PhantomData,
}
}
/// Wrap a FD-backed type into a `Generic` event source using an arbitrary error type.
pub fn new_with_error<E>(file: F, interest: Interest, mode: Mode) -> Generic<F, E> {
Generic {
file: Some(NoIoDrop(file)),
interest,
mode,
token: None,
poller: None,
_error_type: PhantomData,
}
}
}
impl<F: AsFd, E> Generic<F, E> {
/// Unwrap the `Generic` source to retrieve the underlying type
pub fn unwrap(mut self) -> F {
let NoIoDrop(file) = self.file.take().unwrap();
// Remove it from the poller.
if let Some(poller) = self.poller.take() {
poller
.delete(
#[cfg(unix)]
file.as_fd(),
#[cfg(windows)]
file.as_socket(),
)
.ok();
}
file
}
/// Get a reference to the underlying type.
pub fn get_ref(&self) -> &F {
&self.file.as_ref().unwrap().0
}
/// Get a mutable reference to the underlying type.
///
/// # Safety
///
/// This is unsafe because it allows you to modify the underlying type, which
/// allows you to drop the underlying event source. Dropping the underlying source
/// leads to a dangling reference.
pub unsafe fn get_mut(&mut self) -> &mut F {
self.file.as_mut().unwrap().get_mut()
}
}
impl<F: AsFd, E> Drop for Generic<F, E> {
fn drop(&mut self) {
// Remove it from the poller.
if let (Some(file), Some(poller)) = (self.file.take(), self.poller.take()) {
poller
.delete(
#[cfg(unix)]
file.as_fd(),
#[cfg(windows)]
file.as_socket(),
)
.ok();
}
}
}
impl<F, E> EventSource for Generic<F, E>
where
F: AsFd,
E: Into<Box<dyn std::error::Error + Send + Sync>>,
{
type Event = Readiness;
type Metadata = NoIoDrop<F>;
type Ret = Result<PostAction, E>;
type Error = E;
fn process_events<C>(
&mut self,
readiness: Readiness,
token: Token,
mut callback: C,
) -> Result<PostAction, Self::Error>
where
C: FnMut(Self::Event, &mut Self::Metadata) -> Self::Ret,
{
// If the token is invalid or not ours, skip processing.
if self.token != Some(token) {
return Ok(PostAction::Continue);
}
callback(readiness, self.file.as_mut().unwrap())
}
fn register(&mut self, poll: &mut Poll, token_factory: &mut TokenFactory) -> crate::Result<()> {
let token = token_factory.token();
// SAFETY: We ensure that we have a poller to deregister with (see below).
unsafe {
poll.register(
&self.file.as_ref().unwrap().0,
self.interest,
self.mode,
token,
)?;
}
// Make sure we can use the poller to deregister if need be.
// But only if registration actually succeeded
// So that we don't try to unregister the FD on drop if it wasn't registered
// in the first place (for example if registration failed because of a duplicate insertion)
self.poller = Some(poll.poller().clone());
self.token = Some(token);
Ok(())
}
fn reregister(
&mut self,
poll: &mut Poll,
token_factory: &mut TokenFactory,
) -> crate::Result<()> {
let token = token_factory.token();
poll.reregister(
&self.file.as_ref().unwrap().0,
self.interest,
self.mode,
token,
)?;
self.token = Some(token);
Ok(())
}
fn unregister(&mut self, poll: &mut Poll) -> crate::Result<()> {
poll.unregister(&self.file.as_ref().unwrap().0)?;
self.poller = None;
self.token = None;
Ok(())
}
}
#[cfg(all(unix, test))]
mod tests {
use std::io::{Read, Write};
use super::Generic;
use crate::{Dispatcher, Interest, Mode, PostAction};
#[cfg(unix)]
#[test]
fn dispatch_unix() {
use std::os::unix::net::UnixStream;
let mut event_loop = crate::EventLoop::try_new().unwrap();
let handle = event_loop.handle();
let (mut tx, rx) = UnixStream::pair().unwrap();
let generic = Generic::new(rx, Interest::READ, Mode::Level);
let mut dispached = false;
let _generic_token = handle
.insert_source(generic, move |readiness, file, d| {
assert!(readiness.readable);
// we have not registered for writability
assert!(!readiness.writable);
let mut buffer = vec![0; 10];
let ret = (&**file).read(&mut buffer).unwrap();
assert_eq!(ret, 6);
assert_eq!(&buffer[..6], &[1, 2, 3, 4, 5, 6]);
*d = true;
Ok(PostAction::Continue)
})
.unwrap();
event_loop
.dispatch(Some(::std::time::Duration::ZERO), &mut dispached)
.unwrap();
assert!(!dispached);
let ret = tx.write(&[1, 2, 3, 4, 5, 6]).unwrap();
assert_eq!(ret, 6);
tx.flush().unwrap();
event_loop
.dispatch(Some(::std::time::Duration::ZERO), &mut dispached)
.unwrap();
assert!(dispached);
}
#[test]
fn register_deregister_unix() {
use std::os::unix::net::UnixStream;
let mut event_loop = crate::EventLoop::try_new().unwrap();
let handle = event_loop.handle();
let (mut tx, rx) = UnixStream::pair().unwrap();
let generic = Generic::new(rx, Interest::READ, Mode::Level);
let dispatcher = Dispatcher::new(generic, move |_, _, d| {
*d = true;
Ok(PostAction::Continue)
});
let mut dispached = false;
let generic_token = handle.register_dispatcher(dispatcher.clone()).unwrap();
event_loop
.dispatch(Some(::std::time::Duration::ZERO), &mut dispached)
.unwrap();
assert!(!dispached);
// remove the source, and then write something
event_loop.handle().remove(generic_token);
let ret = tx.write(&[1, 2, 3, 4, 5, 6]).unwrap();
assert_eq!(ret, 6);
tx.flush().unwrap();
event_loop
.dispatch(Some(::std::time::Duration::ZERO), &mut dispached)
.unwrap();
// the source has not been dispatched, as the source is no longer here
assert!(!dispached);
// insert it again
let generic = dispatcher.into_source_inner();
let _generic_token = handle
.insert_source(generic, move |readiness, file, d| {
assert!(readiness.readable);
// we have not registered for writability
assert!(!readiness.writable);
let mut buffer = vec![0; 10];
let ret = (&**file).read(&mut buffer).unwrap();
assert_eq!(ret, 6);
assert_eq!(&buffer[..6], &[1, 2, 3, 4, 5, 6]);
*d = true;
Ok(PostAction::Continue)
})
.unwrap();
event_loop
.dispatch(Some(::std::time::Duration::ZERO), &mut dispached)
.unwrap();
// the has now been properly dispatched
assert!(dispached);
}
// Duplicate insertion does not fail on all platforms, but does on Linux
#[cfg(target_os = "linux")]
#[test]
fn duplicate_insert() {
use std::os::unix::{
io::{AsFd, BorrowedFd},
net::UnixStream,
};
let event_loop = crate::EventLoop::<()>::try_new().unwrap();
let handle = event_loop.handle();
let (_, rx) = UnixStream::pair().unwrap();
// Rc only implements AsFd since 1.69...
struct RcFd<T> {
rc: std::rc::Rc<T>,
}
impl<T: AsFd> AsFd for RcFd<T> {
fn as_fd(&self) -> BorrowedFd<'_> {
self.rc.as_fd()
}
}
let rx = std::rc::Rc::new(rx);
let token = handle
.insert_source(
Generic::new(RcFd { rc: rx.clone() }, Interest::READ, Mode::Level),
|_, _, _| Ok(PostAction::Continue),
)
.unwrap();
// inserting the same FD a second time should fail
let ret = handle.insert_source(
Generic::new(RcFd { rc: rx.clone() }, Interest::READ, Mode::Level),
|_, _, _| Ok(PostAction::Continue),
);
assert!(ret.is_err());
std::mem::drop(ret);
// but the original token is still registered
handle.update(&token).unwrap();
}
}