gpio_cdev/
async_tokio.rs

1// Copyright (c) 2018 The rust-gpio-cdev Project Developers.
2//
3// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
4// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
5// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
6// option. This file may not be copied, modified, or distributed
7// except according to those terms.
8
9//! Wrapper for asynchronous programming using Tokio.
10
11use futures::ready;
12use futures::stream::Stream;
13use futures::task::{Context, Poll};
14use tokio::io::unix::{AsyncFd, TryIoError};
15
16use std::os::unix::io::AsRawFd;
17use std::pin::Pin;
18
19use super::event_err;
20use super::{LineEvent, LineEventHandle, Result};
21
22/// Wrapper around a `LineEventHandle` which implements a `futures::stream::Stream` for interrupts.
23///
24/// # Example
25///
26/// The following example waits for state changes on an input line.
27///
28/// ```no_run
29/// use futures::stream::StreamExt;
30/// use gpio_cdev::{AsyncLineEventHandle, Chip, EventRequestFlags, LineRequestFlags};
31///
32/// async fn print_events(line: u32) -> Result<(), gpio_cdev::Error> {
33///     let mut chip = Chip::new("/dev/gpiochip0")?;
34///     let line = chip.get_line(line)?;
35///     let mut events = AsyncLineEventHandle::new(line.events(
36///         LineRequestFlags::INPUT,
37///         EventRequestFlags::BOTH_EDGES,
38///         "gpioevents",
39///     )?)?;
40///
41///     loop {
42///         match events.next().await {
43///             Some(event) => println!("{:?}", event?),
44///             None => break,
45///         };
46///     }
47///
48///     Ok(())
49/// }
50///
51/// # #[tokio::main]
52/// # async fn main() {
53/// #     print_events(42).await.unwrap();
54/// # }
55/// ```
56pub struct AsyncLineEventHandle {
57    asyncfd: AsyncFd<LineEventHandle>,
58}
59
60impl AsyncLineEventHandle {
61    /// Wraps the specified `LineEventHandle`.
62    ///
63    /// # Arguments
64    ///
65    /// * `handle` - handle to be wrapped.
66    pub fn new(handle: LineEventHandle) -> Result<AsyncLineEventHandle> {
67        // The file descriptor needs to be configured for non-blocking I/O for PollEvented to work.
68        let fd = handle.file.as_raw_fd();
69        unsafe {
70            let flags = libc::fcntl(fd, libc::F_GETFL, 0);
71            libc::fcntl(fd, libc::F_SETFL, flags | libc::O_NONBLOCK);
72        }
73
74        Ok(AsyncLineEventHandle {
75            asyncfd: AsyncFd::new(handle)?,
76        })
77    }
78}
79
80impl Stream for AsyncLineEventHandle {
81    type Item = Result<LineEvent>;
82
83    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
84        loop {
85            let mut guard = ready!(self.asyncfd.poll_read_ready_mut(cx))?;
86            match guard.try_io(|inner| inner.get_mut().read_event()) {
87                Err(TryIoError { .. }) => {
88                    // Continue
89                }
90                Ok(Ok(Some(event))) => return Poll::Ready(Some(Ok(event))),
91                Ok(Ok(None)) => return Poll::Ready(Some(Err(event_err(nix::errno::Errno::EIO)))),
92                Ok(Err(err)) => return Poll::Ready(Some(Err(err.into()))),
93            }
94        }
95    }
96}
97
98impl AsRef<LineEventHandle> for AsyncLineEventHandle {
99    fn as_ref(&self) -> &LineEventHandle {
100        self.asyncfd.get_ref()
101    }
102}
gpio_cdev/async_tokio.rs

gpio_cdev/
async_tokio.rs
