Rewrite linux mapper to use epoll instead of threads and blocking IO

Cargo.lock

@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "bitflags"
 version = "1.2.1"
@@ -18,6 +20,16 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
+[[package]]
+name = "epoll"
+version = "4.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "20df693c700404f7e19d4d6fae6b15215d2913c27955d2b9d6f2c0f537511cd0"
+dependencies = [
+ "bitflags",
+ "libc",
+]
+
 [[package]]
 name = "getopts"
 version = "0.2.21"
@@ -94,6 +106,7 @@ dependencies = [
 name = "rusty-keys"
 version = "0.0.3"
 dependencies = [
+ "epoll",
  "getopts",
  "inotify",
  "lazy_static",

Cargo.toml

@@ -32,4 +32,5 @@ lazy_static = "1.4.0"
 [target.'cfg(target_os="linux")'.dependencies]
 libc = "0.2.72"
 nix = "0.17.0"
+epoll = "4.3.1"
 inotify = { version = "0.8.3", default-features = false, features = [] }

src/error.rs

@@ -3,15 +3,9 @@ use std::error;
 use std::ffi;
 use std::io;
 
-#[cfg(target_os = "linux")]
-use std::sync::mpsc;
-
 #[cfg(target_os = "linux")]
 use nix;
 
-#[cfg(target_os = "linux")]
-use libc;
-
 /// UInput error.
 #[derive(Debug)]
 pub enum Error {
@@ -24,14 +18,15 @@ pub enum Error {
 
 	Io(io::Error),
 	
-	#[cfg(target_os = "linux")]
-	Send(mpsc::SendError<libc::input_event>),
+	Toml(toml::de::Error),
 
-	/// The uinput file could not be found.
-	NotFound,
+	NotAKeyboard,
 	
 	/// error reading input_event
 	ShortRead,
+
+	/// epoll already added
+	EpollAlreadyAdded,
 }
 
 impl From<ffi::NulError> for Error {
@@ -53,13 +48,6 @@ impl From<io::Error> for Error {
 	}
 }
 
-#[cfg(target_os = "linux")]
-impl From<mpsc::SendError<libc::input_event>> for Error {
-	fn from(value: mpsc::SendError<libc::input_event>) -> Self {
-		Error::Send(value)
-	}
-}
-
 impl fmt::Display for Error {
 	fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 		match self {
@@ -70,12 +58,13 @@ impl fmt::Display for Error {
 
 			&Error::Io(ref err) => err.fmt(f),
 			
-			#[cfg(target_os = "linux")]
-			&Error::Send(ref err) => err.fmt(f),
+			&Error::Toml(ref err) => err.fmt(f),
 			
-			&Error::NotFound => f.write_str("Device not found."),
+			&Error::NotAKeyboard => f.write_str("This device file is not a keyboard"),
 
 			&Error::ShortRead => f.write_str("Error while reading from device file."),
+			
+			&Error::EpollAlreadyAdded => f.write_str("epoll already added, delete first"),
 		}
 	}
 }

src/keymapper.rs

@@ -470,9 +470,5 @@ fn parse_cfg<P: AsRef<Path>>(path: P) -> Result<KeymapConfig> {
     let mut f = File::open(path)?;
     let mut input = String::new();
     f.read_to_string(&mut input)?;
-    //toml::from_str(&input)?
-    match toml::from_str(&input) {
-        Ok(toml) => Ok(toml),
-        Err(_) => Err(Error::NotFound) // todo: something better
-    }
+    toml::from_str(&input).map_err(|e| Error::Toml(e))
 }

src/linux/device/input_device.rs

@@ -2,54 +2,140 @@ use std::mem;
 use std::fs::File;
 use std::io::Read;
 use std::os::unix::io::AsRawFd;
+use std::os::unix::prelude::RawFd;
 use libc::{input_event, c_int};
-use nix::ioctl_write_ptr;
+use nix::{ioctl_write_ptr, ioctl_read_buf};
+use epoll::ControlOptions::{EPOLL_CTL_ADD, EPOLL_CTL_DEL};
+use nix::fcntl::{OFlag, fcntl, FcntlArg};
+
 use crate::{Error,Result};
+use crate::linux::{EV_KEY, KEY_MAX, NAME, KEY_W, KEY_A, KEY_S, KEY_D};
 
 ioctl_write_ptr!(eviocgrab, b'E', 0x90, c_int);
+ioctl_read_buf!(eviocgname, b'E', 0x06, u8);
+ioctl_read_buf!(eviocgbit, b'E', 0x20, u8);
+ioctl_read_buf!(eviocgbit_ev_key, b'E', 0x20 + EV_KEY, u8);
 
 const SIZE_OF_INPUT_EVENT: usize = mem::size_of::<input_event>();
 
 pub struct InputDevice {
     device_file: File,
-    buf: [u8; SIZE_OF_INPUT_EVENT],
+    grabbed: bool,
+    epoll_fd: Option<RawFd>,
 }
 
 impl InputDevice {
-    pub fn open(device_file: &str) -> Result<Self> {
-        let device_file = File::open(device_file)?;
+    pub fn open<P: AsRef<std::path::Path>>(path: P) -> Result<Self> {
         Ok(InputDevice {
-            device_file: device_file,
-            buf: [0u8; SIZE_OF_INPUT_EVENT],
+            device_file: File::open(path)?,
+            grabbed: false,
+            epoll_fd: None,
         })
     }
     
-    pub fn read_event(&mut self) -> Result<input_event> {
-        let num_bytes = self.device_file.read(&mut self.buf)?;
+    pub fn new_input_event_buf() -> [u8; SIZE_OF_INPUT_EVENT] {
+        [0u8; SIZE_OF_INPUT_EVENT]
+    }
+
+    pub fn read_event(&mut self, buf: &mut [u8; SIZE_OF_INPUT_EVENT]) -> Result<input_event> {
+        let num_bytes = self.device_file.read(buf)?;
         if num_bytes != SIZE_OF_INPUT_EVENT {
             return Err(Error::ShortRead);
         }
-        let event: input_event = unsafe { mem::transmute(self.buf) };
+        let event: input_event = unsafe { mem::transmute(*buf) };
         Ok(event)
     }
 
-    pub fn grab(&mut self) -> Result<()> {
+    pub fn valid_keyboard_device(self) -> Result<Self> {
+        use std::os::unix::fs::FileTypeExt;
+
+        // must be a character device
+        if !self.device_file.metadata()?.file_type().is_char_device() {
+            return Err(Error::NotAKeyboard);
+        }
+        
+        let raw_fd = self.device_file.as_raw_fd();
+
+        // does it support EV_KEY
+        let mut evbit = [0u8; 8];
+        unsafe {
+            eviocgbit(raw_fd, &mut evbit)?;
+        };
+        let evbit = u64::from_ne_bytes(evbit);
+        if (evbit & (1 << EV_KEY)) == 0 {
+            return Err(Error::NotAKeyboard);
+        }
+
+        // does it support all keys WASD ? (yes this is fairly random but probably good enough, could make configuration probably)
+        let mut key_bits = [0u8; (KEY_MAX as usize / 8) + 1];
+        unsafe {
+            eviocgbit_ev_key(raw_fd, &mut key_bits)?;
+        };
+        let key_unsupported = |key : c_int| (key_bits[key as usize / 8] & (1 << (key % 8))) == 0;
+        if key_unsupported(KEY_W) || key_unsupported(KEY_A) || key_unsupported(KEY_S) || key_unsupported(KEY_D) {
+            return Err(Error::NotAKeyboard);
+        }
+
+        // is it another running copy of rusty-keys ?
+        let mut name = [0u8; NAME.len()];
+        unsafe {
+            eviocgname(raw_fd, &mut name)?
+        };
+        if NAME.as_bytes() == &name {
+            return Err(Error::NotAKeyboard);
+        }
+        return Ok(self);
+    }
+
+    pub fn grab(mut self) -> Result<Self> {
         unsafe {
             eviocgrab(self.device_file.as_raw_fd(), 1 as *const c_int)?;
         }
+        self.grabbed = true;
+        Ok(self)
+    }
+
+    pub fn release(&mut self) -> Result<()> {
+        if self.grabbed {
+            unsafe {
+                eviocgrab(self.device_file.as_raw_fd(), 0 as *const c_int)?;
+            }
+            self.grabbed = false;
+        }
         Ok(())
     }
     
-    pub fn release(&mut self) -> Result<()> {
-        unsafe {
-            eviocgrab(self.device_file.as_raw_fd(), 0 as *const c_int)?;
+    pub fn epoll_add(mut self, epoll_fd: RawFd, data: u64) -> Result<Self> {
+        if None != self.epoll_fd {
+            return Err(Error::EpollAlreadyAdded);
         }
-        Ok(())
+        let raw_fd = self.device_file.as_raw_fd();
+        let flags = unsafe {
+            // https://github.com/nix-rust/nix/issues/1102
+            OFlag::from_bits_unchecked(fcntl(raw_fd, FcntlArg::F_GETFL)?)
+        };
+        fcntl(raw_fd, FcntlArg::F_SETFL(flags | OFlag::O_NONBLOCK))?;
+
+        let epoll_event = epoll::Event::new(epoll::Events::EPOLLIN | epoll::Events::EPOLLET, data);
+        epoll::ctl(epoll_fd, EPOLL_CTL_ADD, raw_fd, epoll_event)?;
+        self.epoll_fd = Some(epoll_fd);
+        Ok(self)
+    }
+
+    pub fn epoll_del(&mut self) -> Result<&mut Self> {
+        if let Some(epoll_fd) = self.epoll_fd {
+            let empty_event = epoll::Event::new(epoll::Events::empty(), 0);
+            epoll::ctl(epoll_fd, EPOLL_CTL_DEL, self.device_file.as_raw_fd(), empty_event)?;
+            self.epoll_fd = None;
+        }
+        Ok(self)
     }
 }
 
 impl Drop for InputDevice {
     fn drop(&mut self) {
+        // todo: only release if grabbed
         self.release().ok(); // ignore any errors here, what could we do anyhow?
+        self.epoll_del().ok();
     }
 }

src/linux/mod.rs

@@ -19,9 +19,7 @@ pub fn open<P: AsRef<Path>>(path: P) -> Result<device::Builder> {
 
 use libc::input_event;
 use std::process::exit;
-use std::{env, thread};
-use std::sync::mpsc;
-use std::sync::mpsc::Sender;
+use std::env;
 
 const INPUT_FOLDER: &str = "/dev/input/";
 
@@ -32,7 +30,6 @@ const UP: i32 = 0;
 use getopts::Options;
 
 use inotify::{
-    EventMask,
     Inotify,
     WatchMask,
 };
@@ -101,8 +98,6 @@ impl Keyboard<u16, input_event> for Device {
     }
 }
 
-
-
 #[derive(Debug)]
 struct Config {
     device_files: Vec<String>,
@@ -132,76 +127,107 @@ pub fn main_res() -> Result<()> {
     let mut key_map = LinuxKeyMaps::from_cfg(&key_map, &config.config_file);
     //println!("keymaps: {:?}", keymaps);
 
+    let mut input_event_buf = InputDevice::new_input_event_buf();
+
     if config.device_files.len() == 1 {
-        // shortcut, don't bother with threads
-        let mut input_device = InputDevice::open(&config.device_files[0])?;
-        input_device.grab()?;
+        // shortcut, don't bother with epoll
+        let mut input_device = InputDevice::open(&config.device_files[0])?.grab()?;
 
         loop {
-            let event = input_device.read_event()?;
+            let event = input_device.read_event(&mut input_event_buf)?;
             send_event(&mut key_map, event, &device)?
         }
     } else {
-        // start up some intra thread communication
-        let (tx, rx) = mpsc::channel();
+        let epoll_fd = epoll::create(true)?;
+        const INOTIFY_DATA: u64 = u64::max_value();
 
-        if config.device_files.len() > 0 {
-            // we only want to operate on device files sent in then quit
-            for device_file in config.device_files.iter() {
-                let device_file = device_file.clone();
-                let tx = tx.clone();
-                thread::spawn(move || {
-                    let ret = spawn_map_thread(tx, &device_file);
-                    if let Err(e) = ret {
-                        println!("mapping for {} ended due to error: {}", device_file, e);
-                    }
-                });
-            }
+        let (device_files, mut inotify) = if config.device_files.len() > 0 {
+            // we operate on exactly the devices sent in and never watch for new devices
+            (config.device_files.iter().map(|device_file| InputDevice::open(&device_file).expect("device_file does not exist!")).collect(), None)
         } else {
-            let tx = tx.clone();
-            thread::spawn(move || {
+            use std::os::unix::io::AsRawFd;
             // we want to wait forever starting new threads for any new keyboard devices
-                let mut inotify = Inotify::init().expect("Failed to initialize inotify");
-
-                inotify.add_watch(INPUT_FOLDER, WatchMask::CREATE).expect("Failed to add inotify watch");
-
-                let device_files = get_keyboard_device_filenames();
-                println!("Detected devices: {:?}", device_files);
-                for device_file in device_files.iter() {
-                    inotify_spawn_thread(&tx, device_file);
+            // there is a slight race condition here, if a keyboard is plugged in between the time we
+            // enumerate the devices and set up the inotify watch, we'll miss it, doing it the other way
+            // can bring duplicates though, todo: think about this...
+            let device_files = get_keyboard_devices();
+            let mut inotify = Inotify::init()?;
+            inotify.add_watch(INPUT_FOLDER, WatchMask::CREATE)?;
+            let epoll_event = epoll::Event::new(epoll::Events::EPOLLIN | epoll::Events::EPOLLET, INOTIFY_DATA);
+            epoll::ctl(epoll_fd, epoll::ControlOptions::EPOLL_CTL_ADD, inotify.as_raw_fd(), epoll_event)?;
+            (device_files, Some(inotify))
+        };
+        let mut input_devices = Vec::with_capacity(device_files.len());
+        for (idx, device_file) in device_files.into_iter().enumerate() {
+            input_devices.push(Some(device_file.grab()?.epoll_add(epoll_fd, idx as u64)?));
         }
 
-                let mut buffer = [0u8; 4096];
-                loop {
-                    let events = inotify.read_events_blocking(&mut buffer);
+        let mut epoll_buf = [epoll::Event::new(epoll::Events::empty(), 0); 4];
+        let mut inotify_buf = [0u8; 256];
 
-                    if let Ok(events) = events {
-                        for event in events {
-                            if !event.mask.contains(EventMask::ISDIR) {
-                                if let Some(device_file) = event.name.and_then(|name|name.to_str()) {
+        loop {
+            let num_events = epoll::wait(epoll_fd, -1, &mut epoll_buf)?;
+            for event in &epoll_buf[0..num_events] {
+                let idx = event.data as usize;
+                if let Some(Some(input_device)) = &mut input_devices.get_mut(idx) {
+                    loop {
+                        match input_device.read_event(&mut input_event_buf) {
+                            Ok(event) => {
+                                //println!("input event: {:?}", event);
+                                send_event(&mut key_map, event, &device)?
+                            }
+                            Err(err) => {
+                                if let Error::Io(ref err) = err {
+                                    if err.kind() == std::io::ErrorKind::WouldBlock {
+                                        // go back to epoll event loop
+                                        break;
+                                    }
+                                }
+                                // otherwise it's some other error, don't read anything from this again
+                                println!("input err: {:?}", err);
+                                // remove it from input_devices and drop it
+                                let _ = std::mem::replace(&mut input_devices[idx], None);
+                                if inotify.is_none() {
+                                    // if we aren't watching with inotify, and the last device is removed (Vec only has None's in it), exit the program
+                                    if input_devices.iter().all(|id| id.is_none()) {
+                                        println!("last device went away, exiting...");
+                                        return Ok(());
+                                    }
+                                }
+                                break;
+                            }
+                        }
+                    }
+                } else if event.data == INOTIFY_DATA {
+                    if let Some(inotify) = &mut inotify {
+                        for event in inotify.read_events(&mut inotify_buf)? {
+                            if let Some(device_file) = event.name.and_then(|name| name.to_str()) {
                                 // check if this is an eligible keyboard device
                                 let mut path = std::path::PathBuf::new();
                                 path.push(INPUT_FOLDER);
                                 path.push(device_file);
                                 
-                                    if valid_keyboard_device(path) {
-                                        println!("starting mapping thread for: {}", device_file);
-                                        inotify_spawn_thread(&tx, device_file.clone());
+                                if let Ok(input_device) = InputDevice::open(path).and_then(|id|id.valid_keyboard_device()) {
+                                    println!("starting mapping for new keyboard: {}", device_file);
+
+                                    let idx = input_devices.iter().position(|id| id.is_none()).unwrap_or(input_devices.len());
+
+                                    let input_device = input_device.grab()?.epoll_add(epoll_fd, idx as u64)?;
+
+                                    if idx == input_devices.len() {
+                                        input_devices.push(Some(input_device));
+                                    } else {
+                                        // simply replacing None here
+                                        let _ = std::mem::replace(&mut input_devices[idx], Some(input_device));
+                                    }
                                 }
                             }
                         }
                     }
                 }
             }
-            });
-        }
-        drop(tx); // drop our last one, so when the threads finish, everything stops
-        // process all events
-        for event in rx {
-            send_event(&mut key_map, event, &device)?
         }
     }
-    Ok(())
 }
 
 fn send_event(key_map: &mut LinuxKeyMaps, mut event: input_event, device: &Device) -> Result<()> {
@@ -213,28 +239,6 @@ fn send_event(key_map: &mut LinuxKeyMaps, mut event: input_event, device: &Devic
     Ok(())
 }
 
-fn inotify_spawn_thread(tx: &Sender<input_event>, device_file: &str) {
-    let mut filename = INPUT_FOLDER.to_string();
-    filename.push_str(&device_file);
-    let tx = tx.clone();
-    thread::spawn(move || {
-        let ret = spawn_map_thread(tx, &filename);
-        if let Err(e) = ret {
-            println!("mapping for {} ended due to error: {}", filename, e);
-        }
-    });
-}
-
-fn spawn_map_thread(tx: Sender<input_event>, device_file: &str) -> Result<()> {
-    let mut input_device = InputDevice::open(device_file)?;
-    input_device.grab()?;
-
-    loop {
-        let event = input_device.read_event()?;
-        tx.send(event)?
-    }
-}
-
 fn parse_args() -> Config {
     fn print_usage(program: &str, opts: Options) {
         let brief = format!("Usage: {} [options] [device_files...]", program);
@@ -269,64 +273,13 @@ fn parse_args() -> Config {
     Config::new(matches.free, config_file)
 }
 
-nix::ioctl_read_buf!(eviocgname, b'E', 0x06, u8);
-nix::ioctl_read_buf!(eviocgbit, b'E', 0x20, u8);
-nix::ioctl_read_buf!(eviocgbit_ev_key, b'E', 0x20 + EV_KEY, u8);
-
-fn valid_keyboard_device_res<P: AsRef<Path>>(path: P) -> Result<bool> {
-    use std::fs::File;
-    use std::os::unix::fs::FileTypeExt;
-    use std::os::unix::io::AsRawFd;
-
-    let device_file = File::open(path)?;
-
-    // must be a character device
-    if !device_file.metadata()?.file_type().is_char_device() {
-        return Ok(false);
-    }
-
-    // does it support EV_KEY
-    let mut evbit = [0u8; 8];
-    unsafe {
-        eviocgbit(device_file.as_raw_fd(), &mut evbit)?;
-    };
-    let evbit = u64::from_ne_bytes(evbit);
-    if (evbit & (1 << EV_KEY)) == 0 {
-        return Ok(false);
-    }
-
-    // does it support KEY_A ? todo: check other keys ?
-    let mut key_bits = [0u8; (KEY_MAX as usize / 8) + 1];
-    unsafe {
-        eviocgbit_ev_key(device_file.as_raw_fd(), &mut key_bits)?;
-    };
-    if (key_bits[KEY_A as usize / 8] & (1 << (KEY_A % 8))) == 0 {
-        return Ok(false);
-    }
-
-    // is it another running copy of rusty-keys ?
-    let mut name = [0u8; NAME.len()];
-    unsafe {
-        eviocgname(device_file.as_raw_fd(), &mut name)?
-    };
-    if NAME.as_bytes() == &name {
-        return Ok(false);
-    }
-    return Ok(true);
-}
-
-fn valid_keyboard_device<P: AsRef<Path>>(path: P) -> bool {
-    valid_keyboard_device_res(path).unwrap_or(false)
-}
-
-fn get_keyboard_device_filenames() -> Vec<String> {
+fn get_keyboard_devices() -> Vec<InputDevice> {
     let mut res = Vec::new();
     if let Ok(entries) = std::fs::read_dir(INPUT_FOLDER) {
         for entry in entries {
             if let Ok(entry) = entry {
-                if valid_keyboard_device(entry.path()) {
-                    // these unwrap()'s should not be able to fail if valid_keyboard_device() returns true
-                    res.push(entry.path().file_name().unwrap().to_str().unwrap().to_owned());
+                if let Ok(input_device) = InputDevice::open(entry.path()).and_then(|id|id.valid_keyboard_device()) {
+                    res.push(input_device);
                 }
             }
         }