1 files changed, 180 insertions, 0 deletions
diff --git a/gfx/wr/webrender_api/src/channel.rs b/gfx/wr/webrender_api/src/channel.rs
new file mode 100644
index 0000000000..7d21c6e433
--- /dev/null
+++ b/gfx/wr/webrender_api/src/channel.rs
@@ -0,0 +1,180 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::{Epoch, PipelineId};
+use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use std::io::{self, Cursor, Error, ErrorKind, Read};
+use std::mem;
+
+pub use crossbeam_channel as crossbeam;
+
+#[cfg(not(target_os = "windows"))]
+pub use crossbeam_channel::{Sender, Receiver};
+
+#[cfg(target_os = "windows")]
+pub use std::sync::mpsc::{Sender, Receiver};
+
+#[derive(Clone)]
+pub struct Payload {
+    /// An epoch used to get the proper payload for a pipeline id frame request.
+    ///
+    /// TODO(emilio): Is this still relevant? We send the messages for the same
+    /// pipeline in order, so we shouldn't need it. Seems like this was only
+    /// wallpapering (in most cases) the underlying problem in #991.
+    pub epoch: Epoch,
+    /// A pipeline id to key the payload with, along with the epoch.
+    pub pipeline_id: PipelineId,
+    pub display_list_data: Vec<u8>,
+}
+
+impl Payload {
+    /// Convert the payload to a raw byte vector, in order for it to be
+    /// efficiently shared via shmem, for example.
+    /// This is a helper static method working on a slice.
+    pub fn construct_data(epoch: Epoch, pipeline_id: PipelineId, dl_data: &[u8]) -> Vec<u8> {
+        let mut data = Vec::with_capacity(
+            mem::size_of::<u32>() + 2 * mem::size_of::<u32>() + mem::size_of::<u64>() + dl_data.len(),
+        );
+        data.write_u32::<LittleEndian>(epoch.0).unwrap();
+        data.write_u32::<LittleEndian>(pipeline_id.0).unwrap();
+        data.write_u32::<LittleEndian>(pipeline_id.1).unwrap();
+        data.write_u64::<LittleEndian>(dl_data.len() as u64)
+            .unwrap();
+        data.extend_from_slice(dl_data);
+        data
+    }
+    /// Convert the payload to a raw byte vector, in order for it to be
+    /// efficiently shared via shmem, for example.
+    pub fn to_data(&self) -> Vec<u8> {
+        Self::construct_data(self.epoch, self.pipeline_id, &self.display_list_data)
+    }
+
+    /// Deserializes the given payload from a raw byte vector.
+    pub fn from_data(data: &[u8]) -> Payload {
+        let mut payload_reader = Cursor::new(data);
+        let epoch = Epoch(payload_reader.read_u32::<LittleEndian>().unwrap());
+        let pipeline_id = PipelineId(
+            payload_reader.read_u32::<LittleEndian>().unwrap(),
+            payload_reader.read_u32::<LittleEndian>().unwrap(),
+        );
+
+        let dl_size = payload_reader.read_u64::<LittleEndian>().unwrap() as usize;
+        let mut built_display_list_data = vec![0; dl_size];
+        payload_reader
+            .read_exact(&mut built_display_list_data[..])
+            .unwrap();
+
+        assert_eq!(payload_reader.position(), data.len() as u64);
+
+        Payload {
+            epoch,
+            pipeline_id,
+            display_list_data: built_display_list_data,
+        }
+    }
+}
+
+pub type PayloadSender = MsgSender<Payload>;
+
+pub type PayloadReceiver = MsgReceiver<Payload>;
+
+pub struct MsgReceiver<T> {
+    rx: Receiver<T>,
+}
+
+impl<T> MsgReceiver<T> {
+    pub fn recv(&self) -> Result<T, Error> {
+        self.rx.recv().map_err(|e| io::Error::new(ErrorKind::Other, e.to_string()))
+    }
+
+    pub fn to_crossbeam_receiver(self) -> Receiver<T> {
+        self.rx
+    }
+}
+
+#[derive(Clone)]
+pub struct MsgSender<T> {
+    tx: Sender<T>,
+}
+
+impl<T> MsgSender<T> {
+    pub fn send(&self, data: T) -> Result<(), Error> {
+        self.tx.send(data).map_err(|_| Error::new(ErrorKind::Other, "cannot send on closed channel"))
+    }
+}
+
+pub fn payload_channel() -> Result<(PayloadSender, PayloadReceiver), Error> {
+    let (tx, rx) = unbounded_channel();
+    Ok((PayloadSender { tx }, PayloadReceiver { rx }))
+}
+
+pub fn msg_channel<T>() -> Result<(MsgSender<T>, MsgReceiver<T>), Error> {
+    let (tx, rx) = unbounded_channel();
+    Ok((MsgSender { tx }, MsgReceiver { rx }))
+}
+
+///
+/// These serialize methods are needed to satisfy the compiler
+/// which uses these implementations for the recording tool.
+/// The recording tool only outputs messages that don't contain
+/// Senders or Receivers, so in theory these should never be
+/// called in the in-process config. If they are called,
+/// there may be a bug in the messages that the replay tool is writing.
+///
+
+impl<T> Serialize for MsgSender<T> {
+    fn serialize<S: Serializer>(&self, _: S) -> Result<S::Ok, S::Error> {
+        unreachable!();
+    }
+}
+
+impl<'de, T> Deserialize<'de> for MsgSender<T> {
+    fn deserialize<D>(_: D) -> Result<MsgSender<T>, D::Error>
+                      where D: Deserializer<'de> {
+        unreachable!();
+    }
+}
+
+/// A create a channel intended for one-shot uses, for example the channels
+/// created to block on a synchronous query and then discarded,
+#[cfg(not(target_os = "windows"))]
+pub fn single_msg_channel<T>() -> (Sender<T>, Receiver<T>) {
+    crossbeam_channel::bounded(1)
+}
+
+/// A fast MPMC message channel that can hold a fixed number of messages.
+///
+/// If the channel is full, the sender will block upon sending extra messages
+/// until the receiver has consumed some messages.
+/// The capacity parameter should be chosen either:
+///  - high enough to avoid blocking on the common cases,
+///  - or, on the contrary, using the blocking behavior as a means to prevent
+///    fast producers from building up work faster than it is consumed.
+#[cfg(not(target_os = "windows"))]
+pub fn fast_channel<T>(capacity: usize) -> (Sender<T>, Receiver<T>) {
+    crossbeam_channel::bounded(capacity)
+}
+
+/// Creates an MPMC channel that is a bit slower than the fast_channel but doesn't
+/// have a limit on the number of messages held at a given time and therefore
+/// doesn't block when sending.
+#[cfg(not(target_os = "windows"))]
+pub use crossbeam_channel::unbounded as unbounded_channel;
+
+
+#[cfg(target_os = "windows")]
+pub fn fast_channel<T>(_cap: usize) -> (Sender<T>, Receiver<T>) {
+    std::sync::mpsc::channel()
+}
+
+#[cfg(target_os = "windows")]
+pub fn unbounded_channel<T>() -> (Sender<T>, Receiver<T>) {
+    std::sync::mpsc::channel()
+}
+
+#[cfg(target_os = "windows")]
+pub fn single_msg_channel<T>() -> (Sender<T>, Receiver<T>) {
+    std::sync::mpsc::channel()
+}