gpu_display: add EventDevice to bridge gpu_display to a virtual input device

The EventDevice is a data structure that allows a generic gpu display to
send and receive input events in evdev's format to a generic input
device, such as virtio-input.

BUG=chromium:1023975
TEST=None

Change-Id: Ic663cc8c7a3031aee929e09620c5430c27a25190
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1930406
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Noah Gold <nkgold@google.com>
Tested-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>

2 files changed, 225 insertions, 0 deletions

diff --git a/gpu_display/src/event_device.rs b/gpu_display/src/event_device.rs
new file mode 100644
index 0000000..673a104
--- /dev/null
+++ b/gpu_display/src/event_device.rs
@@ -0,0 +1,222 @@
+// Copyright 2019 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+use std::collections::VecDeque;
+use std::io::{self, Read, Write};
+use std::iter::ExactSizeIterator;
+use std::os::unix::io::{AsRawFd, RawFd};
+use std::os::unix::net::UnixStream;
+
+const EVENT_SIZE: usize = 4;
+const EVENT_BUFFER_LEN_MAX: usize = 16 * EVENT_SIZE;
+
+const EV_SYN: u16 = 0x00;
+const EV_KEY: u16 = 0x01;
+const EV_REL: u16 = 0x02;
+const EV_ABS: u16 = 0x03;
+const SYN_REPORT: u16 = 0;
+const REL_X: u16 = 0x00;
+const REL_Y: u16 = 0x01;
+const ABS_X: u16 = 0x00;
+const ABS_Y: u16 = 0x01;
+
+// /// Half-way build `EventDevice` with only the `event_socket` defined. Finish building the
+// /// `EventDevice` by using `status_socket`.
+// pub struct PartialEventDevice(UnixStream);
+
+// impl PartialEventDevice {
+//     /// Finish build `EventDevice` by providing the `status_socket`.
+//     pub fn status_socket(self, status_socket: UnixStream) -> EventDevice {
+//         EventDevice {
+//             event_socket: self.0,
+//             status_socket,
+//         }
+//     }
+// }
+
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum EventDeviceKind {
+    /// Produces relative mouse motions, wheel, and button clicks while the real mouse is captured.
+    Mouse,
+    /// Produces absolute motion and touch events from the display window's events.
+    Touchscreen,
+    /// Produces key events while the display window has focus.
+    Keyboard,
+}
+
+#[derive(Copy, Clone, Default, PartialEq, Eq, Debug)]
+pub struct EventEncoded {
+    pub type_: u16,
+    pub code: u16,
+    pub value: u32,
+}
+
+impl EventEncoded {
+    #[inline]
+    pub fn syn() -> EventEncoded {
+        EventEncoded {
+            type_: EV_SYN,
+            code: SYN_REPORT,
+            value: 0,
+        }
+    }
+
+    #[inline]
+    pub fn absolute(code: u16, value: u32) -> EventEncoded {
+        EventEncoded {
+            type_: EV_ABS,
+            code,
+            value,
+        }
+    }
+
+    #[inline]
+    pub fn absolute_x(x: u32) -> EventEncoded {
+        Self::absolute(ABS_X, x)
+    }
+
+    #[inline]
+    pub fn absolute_y(y: u32) -> EventEncoded {
+        Self::absolute(ABS_Y, y)
+    }
+
+    #[inline]
+    pub fn key(code: u16, pressed: bool) -> EventEncoded {
+        EventEncoded {
+            type_: EV_KEY,
+            code,
+            value: if pressed { 1 } else { 0 },
+        }
+    }
+
+    #[inline]
+    pub fn from_bytes(v: [u8; 8]) -> EventEncoded {
+        EventEncoded {
+            type_: u16::from_le_bytes([v[0], v[1]]),
+            code: u16::from_le_bytes([v[2], v[3]]),
+            value: u32::from_le_bytes([v[4], v[5], v[6], v[7]]),
+        }
+    }
+
+    #[inline]
+    pub fn to_bytes(&self) -> [u8; 8] {
+        let a = self.type_.to_le_bytes();
+        let b = self.code.to_le_bytes();
+        let c = self.value.to_le_bytes();
+        [a[0], a[1], b[0], b[1], c[0], c[1], c[2], c[3]]
+    }
+}
+
+/// Encapsulates a virtual event device, such as a mouse or keyboard
+pub struct EventDevice {
+    kind: EventDeviceKind,
+    event_buffer: VecDeque<u8>,
+    event_socket: UnixStream,
+}
+
+impl EventDevice {
+    pub fn new(kind: EventDeviceKind, event_socket: UnixStream) -> EventDevice {
+        let _ = event_socket.set_nonblocking(true);
+        EventDevice {
+            kind,
+            event_buffer: Default::default(),
+            event_socket,
+        }
+    }
+
+    #[inline]
+    pub fn mouse(event_socket: UnixStream) -> EventDevice {
+        Self::new(EventDeviceKind::Mouse, event_socket)
+    }
+
+    #[inline]
+    pub fn touchscreen(event_socket: UnixStream) -> EventDevice {
+        Self::new(EventDeviceKind::Touchscreen, event_socket)
+    }
+
+    #[inline]
+    pub fn keyboard(event_socket: UnixStream) -> EventDevice {
+        Self::new(EventDeviceKind::Keyboard, event_socket)
+    }
+
+    #[inline]
+    pub fn kind(&self) -> EventDeviceKind {
+        self.kind
+    }
+
+    /// Flushes the buffered events that did not fit into the underlying transport, if any.
+    ///
+    /// Returns `Ok(true)` if, after this function returns, there all the buffer of events is
+    /// empty.
+    pub fn flush_buffered_events(&mut self) -> io::Result<bool> {
+        while !self.event_buffer.is_empty() {
+            let written = self.event_socket.write(&self.event_buffer.as_slices().0)?;
+            if written == 0 {
+                return Ok(false);
+            }
+            self.event_buffer.drain(..written);
+        }
+        Ok(true)
+    }
+
+    pub fn is_buffered_events_empty(&self) -> bool {
+        self.event_buffer.is_empty()
+    }
+
+    pub fn send_report<E: IntoIterator<Item = EventEncoded>>(
+        &mut self,
+        events: E,
+    ) -> io::Result<bool>
+    where
+        E::IntoIter: ExactSizeIterator,
+    {
+        let it = events.into_iter();
+        if self.event_buffer.len() > (EVENT_BUFFER_LEN_MAX - EVENT_SIZE * (it.len() + 1)) {
+            return Ok(false);
+        }
+
+        for event in it {
+            let bytes = event.to_bytes();
+            self.event_buffer.extend(bytes.iter());
+        }
+
+        self.event_buffer
+            .extend(EventEncoded::syn().to_bytes().iter());
+
+        self.flush_buffered_events()
+    }
+
+    /// Sends the given `event`, returning `Ok(true)` if, after this function returns, there are no
+    /// buffered events remaining.
+    pub fn send_event_encoded(&mut self, event: EventEncoded) -> io::Result<bool> {
+        if !self.flush_buffered_events()? {
+            return Ok(false);
+        }
+
+        let bytes = event.to_bytes();
+        let written = self.event_socket.write(&bytes)?;
+
+        if written == bytes.len() {
+            return Ok(true);
+        }
+
+        if self.event_buffer.len() <= (EVENT_BUFFER_LEN_MAX - EVENT_SIZE) {
+            self.event_buffer.extend(bytes[written..].iter());
+        }
+
+        Ok(false)
+    }
+
+    pub fn recv_event_encoded(&self) -> io::Result<EventEncoded> {
+        let mut event_bytes = [0; 8];
+        (&self.event_socket).read_exact(&mut event_bytes)?;
+        Ok(EventEncoded::from_bytes(event_bytes))
+    }
+}
+
+impl AsRawFd for EventDevice {
+    fn as_raw_fd(&self) -> RawFd {
+        self.event_socket.as_raw_fd()
+    }
+}
diff --git a/gpu_display/src/lib.rs b/gpu_display/src/lib.rs
index 3067c0e..5c243d6 100644
--- a/gpu_display/src/lib.rs
+++ b/gpu_display/src/lib.rs
@@ -11,10 +11,13 @@ use std::path::Path;
 use data_model::VolatileSlice;
 use sys_util::Error as SysError;
 
+mod event_device;
 mod gpu_display_wl;
 #[cfg(feature = "x")]
 mod gpu_display_x;
 
+pub use event_device::{EventDevice, EventDeviceKind, EventEncoded};
+
 /// An error generated by `GpuDisplay`.
 #[derive(Debug)]
 pub enum GpuDisplayError {