Split out shared networking code into net_traits crate

Fixes #4476

components/net_traits/image/base.rs

@@ -0,0 +1,86 @@
+/* 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 png;
+use stb_image::image as stb_image2;
+use std::iter::range_step;
+use util::vec::byte_swap;
+
+// FIXME: Images must not be copied every frame. Instead we should atomically
+// reference count them.
+pub type Image = png::Image;
+
+// TODO(pcwalton): Speed up with SIMD, or better yet, find some way to not do this.
+fn byte_swap_and_premultiply(data: &mut [u8]) {
+    let length = data.len();
+    for i in range_step(0, length, 4) {
+        let r = data[i + 2];
+        let g = data[i + 1];
+        let b = data[i + 0];
+        let a = data[i + 3];
+        data[i + 0] = ((r as u32) * (a as u32) / 255) as u8;
+        data[i + 1] = ((g as u32) * (a as u32) / 255) as u8;
+        data[i + 2] = ((b as u32) * (a as u32) / 255) as u8;
+    }
+}
+
+pub fn load_from_memory(buffer: &[u8]) -> Option<Image> {
+    if buffer.len() == 0 {
+        return None;
+    }
+
+    if png::is_png(buffer) {
+        match png::load_png_from_memory(buffer) {
+            Ok(mut png_image) => {
+                match png_image.pixels {
+                    png::PixelsByColorType::RGB8(ref mut data) => byte_swap(data.as_mut_slice()),
+                    png::PixelsByColorType::RGBA8(ref mut data) => {
+                        byte_swap_and_premultiply(data.as_mut_slice())
+                    }
+                    _ => {}
+                }
+                Some(png_image)
+            }
+            Err(_err) => None,
+        }
+    } else {
+        // For non-png images, we use stb_image
+        // Can't remember why we do this. Maybe it's what cairo wants
+        static FORCE_DEPTH: uint = 4;
+
+        match stb_image2::load_from_memory_with_depth(buffer, FORCE_DEPTH, true) {
+            stb_image2::LoadResult::ImageU8(mut image) => {
+                assert!(image.depth == 4);
+                // handle gif separately because the alpha-channel has to be premultiplied
+                if is_gif(buffer) {
+                    byte_swap_and_premultiply(image.data.as_mut_slice());
+                } else {
+                    byte_swap(image.data.as_mut_slice());
+                }
+                Some(png::Image {
+                    width: image.width as u32,
+                    height: image.height as u32,
+                    pixels: png::PixelsByColorType::RGBA8(image.data)
+                })
+            }
+            stb_image2::LoadResult::ImageF32(_image) => {
+                error!("HDR images not implemented");
+                None
+            }
+            stb_image2::LoadResult::Error(e) => {
+                error!("stb_image failed: {}", e);
+                None
+            }
+        }
+    }
+}
+
+fn is_gif(buffer: &[u8]) -> bool {
+    match buffer {
+        [b'G',b'I',b'F',b'8', n, b'a', ..] if n == b'7' || n == b'9' => true,
+        _ => false
+    }
+}
+
+

components/net_traits/image/holder.rs

@@ -0,0 +1,101 @@
+/* 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 image::base::Image;
+use image_cache_task::ImageResponseMsg;
+use local_image_cache::LocalImageCache;
+
+use geom::size::Size2D;
+use std::sync::{Arc, Mutex};
+use url::Url;
+
+// FIXME: Nasty coupling here This will be a problem if we want to factor out image handling from
+// the network stack. This should probably be factored out into an interface and use dependency
+// injection.
+
+/// A struct to store image data. The image will be loaded once the first time it is requested,
+/// and an Arc will be stored.  Clones of this Arc are given out on demand.
+#[derive(Clone)]
+pub struct ImageHolder<NodeAddress> {
+    url: Url,
+    image: Option<Arc<Box<Image>>>,
+    cached_size: Size2D<int>,
+    local_image_cache: Arc<Mutex<LocalImageCache<NodeAddress>>>,
+}
+
+impl<NodeAddress: Send + 'static> ImageHolder<NodeAddress> {
+    pub fn new(url: Url, local_image_cache: Arc<Mutex<LocalImageCache<NodeAddress>>>)
+               -> ImageHolder<NodeAddress> {
+        debug!("ImageHolder::new() {}", url.serialize());
+        let holder = ImageHolder {
+            url: url,
+            image: None,
+            cached_size: Size2D(0,0),
+            local_image_cache: local_image_cache.clone(),
+        };
+
+        // Tell the image cache we're going to be interested in this url
+        // FIXME: These two messages must be sent to prep an image for use
+        // but they are intended to be spread out in time. Ideally prefetch
+        // should be done as early as possible and decode only once we
+        // are sure that the image will be used.
+        {
+            let val = holder.local_image_cache.lock().unwrap();
+            let mut local_image_cache = val;
+            local_image_cache.prefetch(&holder.url);
+            local_image_cache.decode(&holder.url);
+        }
+
+        holder
+    }
+
+    /// This version doesn't perform any computation, but may be stale w.r.t. newly-available image
+    /// data that determines size.
+    ///
+    /// The intent is that the impure version is used during layout when dimensions are used for
+    /// computing layout.
+    pub fn size(&self) -> Size2D<int> {
+        self.cached_size
+    }
+
+    /// Query and update the current image size.
+    pub fn get_size(&mut self, node_address: NodeAddress) -> Option<Size2D<int>> {
+        debug!("get_size() {}", self.url.serialize());
+        self.get_image(node_address).map(|img| {
+            self.cached_size = Size2D(img.width as int,
+                                      img.height as int);
+            self.cached_size.clone()
+        })
+    }
+
+    pub fn get_image_if_present(&self) -> Option<Arc<Box<Image>>> {
+        debug!("get_image_if_present() {}", self.url.serialize());
+        self.image.clone()
+    }
+
+    pub fn get_image(&mut self, node_address: NodeAddress) -> Option<Arc<Box<Image>>> {
+        debug!("get_image() {}", self.url.serialize());
+
+        // If this is the first time we've called this function, load
+        // the image and store it for the future
+        if self.image.is_none() {
+            let port = {
+                let val = self.local_image_cache.lock().unwrap();
+                let mut local_image_cache = val;
+                local_image_cache.get_image(node_address, &self.url)
+            };
+            match port.recv().unwrap() {
+                ImageResponseMsg::ImageReady(image) => self.image = Some(image),
+                ImageResponseMsg::ImageNotReady => debug!("image not ready for {}", self.url.serialize()),
+                ImageResponseMsg::ImageFailed => debug!("image decoding failed for {}", self.url.serialize()),
+            }
+        }
+
+        return self.image.clone();
+    }
+
+    pub fn url(&self) -> &Url {
+        &self.url
+    }
+}