1 files changed, 156 insertions, 0 deletions
diff --git a/src/servo-net/local_image_cache.rs b/src/servo-net/local_image_cache.rs
new file mode 100644
index 00000000000..8df7f082bb7
--- /dev/null
+++ b/src/servo-net/local_image_cache.rs
@@ -0,0 +1,156 @@
+/* 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 clone_arc = std::arc::clone;
+use core::comm::Port;
+use servo_util::url::{UrlMap, url_map};
+use std::net::url::Url;
+
+pub fn LocalImageCache(image_cache_task: ImageCacheTask) -> LocalImageCache {
+    LocalImageCache {
+        image_cache_task: image_cache_task,
+        round_number: 1,
+        mut on_image_available: None,
+        state_map: url_map()
+    }
+}
+
+pub struct LocalImageCache {
+    priv image_cache_task: ImageCacheTask,
+    priv round_number: uint,
+    priv on_image_available: Option<@fn() -> ~fn(ImageResponseMsg)>,
+    priv state_map: UrlMap<@mut ImageState>
+}
+
+priv struct ImageState {
+    prefetched: bool,
+    decoded: bool,
+    last_request_round: uint,
+    last_response: ImageResponseMsg
+}
+
+#[allow(non_implicitly_copyable_typarams)] // Using maps of Urls
+pub 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
+    // FIXME: 'pub' is an unexpected token?
+    /* pub */ fn next_round(&mut self, on_image_available: @fn() -> ~fn(ImageResponseMsg)) {
+        self.round_number += 1;
+        self.on_image_available = Some(on_image_available);
+    }
+
+    pub fn prefetch(&self, url: &Url) {
+        let state = self.get_state(url);
+        if !state.prefetched {
+            self.image_cache_task.send(Prefetch(copy *url));
+            state.prefetched = true;
+        }
+    }
+
+    pub fn decode(&self, url: &Url) {
+        let state = self.get_state(url);
+        if !state.decoded {
+            self.image_cache_task.send(Decode(copy *url));
+            state.decoded = true;
+        }
+    }
+
+    // FIXME: Should return a Future
+    pub fn get_image(&self, url: &Url) -> Port<ImageResponseMsg> {
+        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 = self.round_number;
+
+        match state.last_response {
+            ImageReady(ref image) => {
+                // FIXME: appease borrowck
+                unsafe {
+                    let (port, chan) = comm::stream();
+                    chan.send(ImageReady(clone_arc(image)));
+                    return port;
+                }
+            }
+            ImageNotReady => {
+                if last_round == self.round_number {
+                    let (port, chan) = comm::stream();
+                    chan.send(ImageNotReady);
+                    return port;
+                } else {
+                    // We haven't requested the image from the
+                    // remote cache this round
+                }
+            }
+            ImageFailed => {
+                let (port, chan) = comm::stream();
+                chan.send(ImageFailed);
+                return port;
+            }
+        }
+
+        let (response_port, response_chan) = comm::stream();
+        self.image_cache_task.send(GetImage(copy *url, 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 = self.on_image_available.get()();
+                let url = copy *url;
+                do task::spawn {
+                    let (response_port, response_chan) = comm::stream();
+                    image_cache_task.send(WaitForImage(copy url, 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(clone_arc(image)),
+            ImageNotReady => ImageNotReady,
+            ImageFailed => ImageFailed
+        };
+        state.last_response = response_copy;
+
+        let (port, chan) = comm::stream();
+        chan.send(response);
+        return port;
+    }
+
+    priv fn get_state(&self, url: &Url) -> @mut ImageState {
+        match self.state_map.find(url) {
+            Some(state) => *state,
+            None => {
+                let new_state = @mut ImageState {
+                    prefetched: false,
+                    decoded: false,
+                    last_request_round: 0,
+                    last_response: ImageNotReady
+                };
+                self.state_map.insert(copy *url, new_state);
+                self.get_state(url)
+            }
+        }
+    }
+}
+