Fetch cancellation: Add CancellationListener

components/net/fetch/methods.rs

@@ -28,7 +28,7 @@ use std::fs::File;
 use std::io::Read;
 use std::mem;
 use std::str;
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 use std::sync::mpsc::{Sender, Receiver};
 use subresource_integrity::is_response_integrity_valid;
 
@@ -44,9 +44,37 @@ pub struct FetchContext {
     pub user_agent: Cow<'static, str>,
     pub devtools_chan: Option<Sender<DevtoolsControlMsg>>,
     pub filemanager: FileManager,
-    pub cancel_chan: Option<IpcReceiver<()>>,
+    pub cancellation_listener: Arc<Mutex<CancellationListener>>,
 }
 
+pub struct CancellationListener {
+    cancel_chan: Option<IpcReceiver<()>>,
+    cancelled: bool,
+}
+
+impl CancellationListener {
+    pub fn new(cancel_chan: Option<IpcReceiver<()>>) -> Self {
+        Self {
+            cancel_chan: cancel_chan,
+            cancelled: false,
+        }
+    }
+
+    pub fn cancelled(&mut self) -> bool {
+        if let Some(ref cancel_chan) = self.cancel_chan {
+            if self.cancelled {
+                true
+            } else if cancel_chan.try_recv().is_ok() {
+                self.cancelled = true;
+                true
+            } else {
+                false
+            }
+        } else {
+            false
+        }
+    }
+}
 pub type DoneChannel = Option<(Sender<Data>, Receiver<Data>)>;
 
 /// [Fetch](https://fetch.spec.whatwg.org#concept-fetch)