Add support for reading asynchronously with mio::Evented and tokio_core::Stream

.gitignore

@@ -3,6 +3,7 @@
 *.so
 *.rlib
 *.dll
+*.bk
 
 # Executables
 *.exe

.travis.yml

@@ -1,7 +1,7 @@
 language: rust
 sudo: false
 rust:
-  - 1.5.0
+  - 1.10.0
   - stable
   - beta
   - nightly
@@ -25,9 +25,13 @@ env:
 
 script:
   - |
-    travis-cargo build &&
-    travis-cargo test &&
-    travis-cargo --only stable doc
+    travis-cargo build -- --features=tokio &&
+    travis-cargo test -- --features=tokio &&
+    travis-cargo build -- --features=mio-evented &&
+    travis-cargo test -- --features=mio-evented &&
+    travis-cargo build -- &&
+    travis-cargo test -- &&
+    travis-cargo --only stable doc -- --features=tokio
 
 after_success:
   - travis-cargo --only stable doc-upload

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sysfs_gpio"
-version = "0.4.4"
+version = "0.5.0"
 authors = ["Paul Osborne <osbpau@gmail.com>"]
 license = "MIT/Apache-2.0"
 repository = "/~https://github.com/rust-embedded/rust-sysfs-gpio"
@@ -15,6 +15,13 @@ interrupts) GPIOs from userspace.
 See https://www.kernel.org/doc/Documentation/gpio/sysfs.txt
 """
 
+[features]
+mio-evented = ["mio"]
+tokio = ["futures", "tokio-core", "mio-evented"]
+
 [dependencies]
+futures = { version = "0.1", optional = true }
 nix = "0.6.0"
 regex = "0.1.0"
+mio = { version = "0.6", optional = true }
+tokio-core = { version = "0.1", optional = true }

README.md

@@ -66,6 +66,7 @@ More Examples:
 - [Blink an LED](examples/blinky.rs)
 - [Poll a GPIO Input](examples/poll.rs)
 - [Receive interrupt on GPIO Change](examples/interrupt.rs)
+- [Poll several pins asynchronously with Tokio](examples/tokio.rs)
 - [gpio-utils Project (uses most features)](/~https://github.com/rust-embedded/gpio-utils)
 
 Features
@@ -81,6 +82,8 @@ The following features are planned for the library:
 - [ ] Support for configuring whether a pin is active low/high
 - [x] Support for configuring interrupts on GPIO
 - [x] Support for polling on GPIO with configured interrupt
+- [x] Support for asynchronous polling using `mio` or `tokio-core` (requires
+      enabling the `mio-evented` or `tokio` crate features, respectively)
 
 Cross Compiling
 ---------------

examples/tokio.rs

@@ -0,0 +1,60 @@
+#[cfg(feature = "tokio")]
+extern crate futures;
+#[cfg(feature = "tokio")]
+extern crate sysfs_gpio;
+#[cfg(feature = "tokio")]
+extern crate tokio_core;
+
+#[cfg(feature = "tokio")]
+use futures::{Future, Stream};
+#[cfg(feature = "tokio")]
+use sysfs_gpio::{Direction, Edge, Pin};
+#[cfg(feature = "tokio")]
+use std::env;
+#[cfg(feature = "tokio")]
+use tokio_core::reactor::Core;
+
+#[cfg(feature = "tokio")]
+fn stream(pin_nums: Vec<u64>) -> sysfs_gpio::Result<()> {
+    // NOTE: this currently runs forever and as such if
+    // the app is stopped (Ctrl-C), no cleanup will happen
+    // and the GPIO will be left exported.  Not much
+    // can be done about this as Rust signal handling isn't
+    // really present at the moment.  Revisit later.
+    let pins: Vec<_> = pin_nums.iter().map(|&p| (p, Pin::new(p))).collect();
+    let mut l = try!(Core::new());
+    let handle = l.handle();
+    for &(i, ref pin) in pins.iter() {
+        try!(pin.export());
+        try!(pin.set_direction(Direction::In));
+        try!(pin.set_edge(Edge::BothEdges));
+        handle.spawn(try!(pin.get_value_stream(&handle))
+            .for_each(move |val| {
+                println!("Pin {} changed value to {}", i, val);
+                Ok(())
+            })
+            .map_err(|_| ()));
+    }
+    // Wait forever for events
+    loop {
+        l.turn(None)
+    }
+}
+
+#[cfg(feature = "tokio")]
+fn main() {
+    let pins: Vec<u64> = env::args()
+        .skip(1)
+        .map(|a| a.parse().expect("Pins must be specified as integers"))
+        .collect();
+    if pins.is_empty() {
+        println!("Usage: ./tokio <pin> [pin ...]");
+    } else {
+        stream(pins).unwrap();
+    }
+}
+
+#[cfg(not(feature = "tokio"))]
+fn main() {
+    println!("This example requires the `tokio` feature to be enabled.");
+}

src/lib.rs

@@ -44,8 +44,22 @@
 //! }
 //! ```
 
+#[cfg(feature = "tokio")]
+extern crate futures;
+#[cfg(feature = "mio-evented")]
+extern crate mio;
 extern crate nix;
 extern crate regex;
+#[cfg(feature = "tokio")]
+extern crate tokio_core;
+
+#[cfg(feature = "tokio")]
+use futures::{Async, Poll, Stream};
+
+#[cfg(feature = "mio-evented")]
+use mio::Evented;
+#[cfg(feature = "mio-evented")]
+use mio::unix::EventedFd;
 
 use nix::sys::epoll::*;
 use nix::unistd::close;
@@ -57,6 +71,9 @@ use std::fs;
 use std::fs::File;
 use std::path::Path;
 
+#[cfg(feature = "tokio")]
+use tokio_core::reactor::{Handle, PollEvented};
+
 mod error;
 pub use error::Error;
 
@@ -395,6 +412,44 @@ impl Pin {
     pub fn get_poller(&self) -> Result<PinPoller> {
         PinPoller::new(self.pin_num)
     }
+
+    /// Get an AsyncPinPoller object for this pin
+    ///
+    /// The async pin poller object can be used with the `mio` crate. You should probably call
+    /// `set_edge()` before using this.
+    ///
+    /// This method is only available when the `mio-evented` crate feature is enabled.
+    #[cfg(feature = "mio-evented")]
+    pub fn get_async_poller(&self) -> Result<AsyncPinPoller> {
+        AsyncPinPoller::new(self.pin_num)
+    }
+
+    /// Get a Stream of pin interrupts for this pin
+    ///
+    /// The PinStream object can be used with the `tokio-core` crate. You should probably call
+    /// `set_edge()` before using this.
+    ///
+    /// This method is only available when the `tokio` crate feature is enabled.
+    #[cfg(feature = "tokio")]
+    pub fn get_stream(&self, handle: &Handle) -> Result<PinStream> {
+        PinStream::init(self.clone(), handle)
+    }
+
+    /// Get a Stream of pin values for this pin
+    ///
+    /// The PinStream object can be used with the `tokio-core` crate. You should probably call
+    /// `set_edge(Edge::BothEdges)` before using this.
+    ///
+    /// Note that the values produced are the value of the pin as soon as we get to handling the
+    /// interrupt in userspace.  Each time this stream produces a value, a change has occurred, but
+    /// it could end up producing the same value multiple times if the value has changed back
+    /// between when the interrupt occurred and when the value was read.
+    ///
+    /// This method is only available when the `tokio` crate feature is enabled.
+    #[cfg(feature = "tokio")]
+    pub fn get_value_stream(&self, handle: &Handle) -> Result<PinValueStream> {
+        Ok(PinValueStream(try!(PinStream::init(self.clone(), handle))))
+    }
 }
 
 #[derive(Debug)]
@@ -445,9 +500,9 @@ impl PinPoller {
     /// of interrupts which may result in this call returning
     /// may be configured by calling `set_edge()` prior to
     /// making this call.  This call makes use of epoll under the
-    /// covers.  If it is desirable to poll on multiple GPIOs or
-    /// other event source, you will need to implement that logic
-    /// yourself.
+    /// covers.  To poll on multiple GPIOs or other event sources,
+    /// poll asynchronously using the integration with either `mio`
+    /// or `tokio_core`.
     ///
     /// This function will return Some(value) of the pin if a change is
     /// detected or None if a timeout occurs.  Note that the value provided
@@ -479,3 +534,108 @@ impl Drop for PinPoller {
         close(self.epoll_fd).unwrap();  // panic! if close files
     }
 }
+
+#[cfg(feature = "mio-evented")]
+#[derive(Debug)]
+pub struct AsyncPinPoller {
+    devfile: File,
+}
+
+#[cfg(feature = "mio-evented")]
+impl AsyncPinPoller {
+    fn new(pin_num: u64) -> Result<Self> {
+        let devfile = try!(File::open(&format!("/sys/class/gpio/gpio{}/value", pin_num)));
+        Ok(AsyncPinPoller { devfile: devfile })
+    }
+}
+
+#[cfg(feature = "mio-evented")]
+impl Evented for AsyncPinPoller {
+    fn register(&self,
+                poll: &mio::Poll,
+                token: mio::Token,
+                interest: mio::Ready,
+                opts: mio::PollOpt)
+                -> io::Result<()> {
+        EventedFd(&self.devfile.as_raw_fd()).register(poll, token, interest, opts)
+    }
+
+    fn reregister(&self,
+                  poll: &mio::Poll,
+                  token: mio::Token,
+                  interest: mio::Ready,
+                  opts: mio::PollOpt)
+                  -> io::Result<()> {
+        EventedFd(&self.devfile.as_raw_fd()).reregister(poll, token, interest, opts)
+    }
+
+    fn deregister(&self, poll: &mio::Poll) -> io::Result<()> {
+        EventedFd(&self.devfile.as_raw_fd()).deregister(poll)
+    }
+}
+
+#[cfg(feature = "tokio")]
+pub struct PinStream {
+    evented: PollEvented<AsyncPinPoller>,
+    skipped_first_event: bool,
+}
+
+#[cfg(feature = "tokio")]
+impl PinStream {
+    pub fn init(pin: Pin, handle: &Handle) -> Result<Self> {
+        Ok(PinStream {
+            evented: try!(PollEvented::new(try!(pin.get_async_poller()), &handle)),
+            skipped_first_event: false,
+        })
+    }
+}
+
+#[cfg(feature = "tokio")]
+impl Stream for PinStream {
+    type Item = ();
+    type Error = Error;
+
+    fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
+        Ok(match self.evented.poll_read() {
+            Async::Ready(()) => {
+                self.evented.need_read();
+                if self.skipped_first_event {
+                    Async::Ready(Some(()))
+                } else {
+                    self.skipped_first_event = true;
+                    Async::NotReady
+                }
+            }
+            Async::NotReady => Async::NotReady,
+        })
+    }
+}
+
+#[cfg(feature = "tokio")]
+pub struct PinValueStream(PinStream);
+
+#[cfg(feature = "tokio")]
+impl PinValueStream {
+    #[inline]
+    fn get_value(&mut self) -> Result<u8> {
+        get_value_from_file(&mut self.0.evented.get_mut().devfile)
+    }
+}
+
+#[cfg(feature = "tokio")]
+impl Stream for PinValueStream {
+    type Item = u8;
+    type Error = Error;
+
+    fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
+        match self.0.poll() {
+            Ok(Async::Ready(Some(()))) => {
+                let value = try!(self.get_value());
+                Ok(Async::Ready(Some(value)))
+            }
+            Ok(Async::Ready(None)) => Ok(Async::Ready(None)),
+            Ok(Async::NotReady) => Ok(Async::NotReady),
+            Err(e) => Err(e),
+        }
+    }
+}