Cargoify servo

components/net/local_image_cache.rs

@@ -0,0 +1,166 @@
+/* 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/. */
+
+/*!
+An adapter for ImageCacheTask that does local caching to avoid
+extra message traffic, it also avoids waiting on the same image
+multiple times and thus triggering reflows multiple times.
+*/
+
+use image_cache_task::{Decode, GetImage, ImageCacheTask, ImageFailed, ImageNotReady, ImageReady};
+use image_cache_task::{ImageResponseMsg, Prefetch, WaitForImage};
+
+use std::comm::{Receiver, channel};
+use std::collections::hashmap::HashMap;
+use servo_util::task::spawn_named;
+use url::Url;
+
+pub trait ImageResponder {
+    fn respond(&self) -> proc(ImageResponseMsg):Send;
+}
+
+pub struct LocalImageCache {
+    image_cache_task: ImageCacheTask,
+    round_number: uint,
+    on_image_available: Option<Box<ImageResponder+Send>>,
+    state_map: HashMap<Url, ImageState>
+}
+
+impl LocalImageCache {
+    pub fn new(image_cache_task: ImageCacheTask) -> LocalImageCache {
+        LocalImageCache {
+            image_cache_task: image_cache_task,
+            round_number: 1,
+            on_image_available: None,
+            state_map: HashMap::new()
+        }
+    }
+}
+
+#[deriving(Clone)]
+struct ImageState {
+    prefetched: bool,
+    decoded: bool,
+    last_request_round: uint,
+    last_response: ImageResponseMsg
+}
+
+impl LocalImageCache {
+    /// The local cache will only do a single remote request for a given
+    /// URL in each 'round'. Layout should call this each time it begins
+    pub fn next_round(&mut self, on_image_available: Box<ImageResponder+Send>) {
+        self.round_number += 1;
+        self.on_image_available = Some(on_image_available);
+    }
+
+    pub fn prefetch(&mut self, url: &Url) {
+        {
+            let state = self.get_state(url);
+            if state.prefetched {
+                return
+            }
+
+            state.prefetched = true;
+        }
+
+        self.image_cache_task.send(Prefetch((*url).clone()));
+    }
+
+    pub fn decode(&mut self, url: &Url) {
+        {
+            let state = self.get_state(url);
+            if state.decoded {
+                return
+            }
+            state.decoded = true;
+        }
+
+        self.image_cache_task.send(Decode((*url).clone()));
+    }
+
+    // FIXME: Should return a Future
+    pub fn get_image(&mut self, url: &Url) -> Receiver<ImageResponseMsg> {
+        {
+            let round_number = self.round_number;
+            let state = self.get_state(url);
+
+            // Save the previous round number for comparison
+            let last_round = state.last_request_round;
+            // Set the current round number for this image
+            state.last_request_round = round_number;
+
+            match state.last_response {
+                ImageReady(ref image) => {
+                    let (chan, port) = channel();
+                    chan.send(ImageReady(image.clone()));
+                    return port;
+                }
+                ImageNotReady => {
+                    if last_round == round_number {
+                        let (chan, port) = channel();
+                        chan.send(ImageNotReady);
+                        return port;
+                    } else {
+                        // We haven't requested the image from the
+                        // remote cache this round
+                    }
+                }
+                ImageFailed => {
+                    let (chan, port) = channel();
+                    chan.send(ImageFailed);
+                    return port;
+                }
+            }
+        }
+
+        let (response_chan, response_port) = channel();
+        self.image_cache_task.send(GetImage((*url).clone(), response_chan));
+
+        let response = response_port.recv();
+        match response {
+            ImageNotReady => {
+                // Need to reflow when the image is available
+                // FIXME: Instead we should be just passing a Future
+                // to the caller, then to the display list. Finally,
+                // the compositor should be resonsible for waiting
+                // on the image to load and triggering layout
+                let image_cache_task = self.image_cache_task.clone();
+                assert!(self.on_image_available.is_some());
+                let on_image_available: proc(ImageResponseMsg):Send = self.on_image_available.as_ref().unwrap().respond();
+                let url = (*url).clone();
+                spawn_named("LocalImageCache", proc() {
+                    let (response_chan, response_port) = channel();
+                    image_cache_task.send(WaitForImage(url.clone(), response_chan));
+                    on_image_available(response_port.recv());
+                });
+            }
+            _ => ()
+        }
+
+        // Put a copy of the response in the cache
+        let response_copy = match response {
+            ImageReady(ref image) => ImageReady(image.clone()),
+            ImageNotReady => ImageNotReady,
+            ImageFailed => ImageFailed
+        };
+        self.get_state(url).last_response = response_copy;
+
+        let (chan, port) = channel();
+        chan.send(response);
+        return port;
+    }
+
+    fn get_state<'a>(&'a mut self, url: &Url) -> &'a mut ImageState {
+        let state = self.state_map.find_or_insert_with(url.clone(), |_| {
+            let new_state = ImageState {
+                prefetched: false,
+                decoded: false,
+                last_request_round: 0,
+                last_response: ImageNotReady
+            };
+            new_state
+        });
+        state
+    }
+}