Prefetch img and scripts during parsing

components/net/resource_thread.rs

@@ -25,11 +25,12 @@ use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
 use net_traits::request::{Destination, RequestBuilder};
 use net_traits::response::{Response, ResponseInit};
 use net_traits::storage_thread::StorageThreadMsg;
+use net_traits::FetchTaskTarget;
 use net_traits::WebSocketNetworkEvent;
 use net_traits::{CookieSource, CoreResourceMsg, CoreResourceThread};
 use net_traits::{CustomResponseMediator, FetchChannels};
-use net_traits::{FetchResponseMsg, ResourceThreads, WebSocketDomAction};
 use net_traits::{ResourceFetchTiming, ResourceTimingType};
+use net_traits::{ResourceThreads, WebSocketDomAction};
 use profile_traits::mem::ProfilerChan as MemProfilerChan;
 use profile_traits::mem::{Report, ReportKind, ReportsChan};
 use profile_traits::time::ProfilerChan;
@@ -245,6 +246,10 @@ impl ResourceChannelManager {
                     action_receiver,
                     http_state,
                 ),
+                FetchChannels::Prefetch => {
+                    self.resource_manager
+                        .fetch(req_init, None, (), http_state, None)
+                },
             },
             CoreResourceMsg::DeleteCookies(request) => {
                 http_state
@@ -455,11 +460,11 @@ impl CoreResourceManager {
         }
     }
 
-    fn fetch(
+    fn fetch<Target: 'static + FetchTaskTarget + Send>(
         &self,
         request_builder: RequestBuilder,
         res_init_: Option<ResponseInit>,
-        mut sender: IpcSender<FetchResponseMsg>,
+        mut sender: Target,
         http_state: &Arc<HttpState>,
         cancel_chan: Option<IpcReceiver<()>>,
     ) {

components/net_traits/lib.rs

@@ -237,6 +237,18 @@ impl FetchTaskTarget for IpcSender<FetchResponseMsg> {
     }
 }
 
+impl FetchTaskTarget for () {
+    fn process_request_body(&mut self, _: &Request) {}
+
+    fn process_request_eof(&mut self, _: &Request) {}
+
+    fn process_response(&mut self, _: &Response) {}
+
+    fn process_response_chunk(&mut self, _: Vec<u8>) {}
+
+    fn process_response_eof(&mut self, _: &Response) {}
+}
+
 pub trait Action<Listener> {
     fn process(self, listener: &mut Listener);
 }
@@ -368,6 +380,9 @@ pub enum FetchChannels {
         event_sender: IpcSender<WebSocketNetworkEvent>,
         action_receiver: IpcReceiver<WebSocketDomAction>,
     },
+    /// If the fetch is just being done to populate the cache,
+    /// not because the data is needed now.
+    Prefetch,
 }
 
 #[derive(Debug, Deserialize, Serialize)]

components/script/dom/bindings/trace.rs

@@ -80,7 +80,7 @@ use msg::constellation_msg::{
 use net_traits::filemanager_thread::RelativePos;
 use net_traits::image::base::{Image, ImageMetadata};
 use net_traits::image_cache::{ImageCache, PendingImageId};
-use net_traits::request::{Request, RequestBuilder};
+use net_traits::request::{Referrer, Request, RequestBuilder};
 use net_traits::response::HttpsState;
 use net_traits::response::{Response, ResponseBody};
 use net_traits::storage_thread::StorageType;
@@ -456,6 +456,7 @@ unsafe_no_jsmanaged_fields!(Request);
 unsafe_no_jsmanaged_fields!(RequestBuilder);
 unsafe_no_jsmanaged_fields!(StyleSharedRwLock);
 unsafe_no_jsmanaged_fields!(USVString);
+unsafe_no_jsmanaged_fields!(Referrer);
 unsafe_no_jsmanaged_fields!(ReferrerPolicy);
 unsafe_no_jsmanaged_fields!(Response);
 unsafe_no_jsmanaged_fields!(ResponseBody);

components/script/dom/htmlimageelement.rs

@@ -53,6 +53,7 @@ use html5ever::{LocalName, Prefix};
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
 use mime::{self, Mime};
+use msg::constellation_msg::PipelineId;
 use net_traits::image::base::{Image, ImageMetadata};
 use net_traits::image_cache::UsePlaceholder;
 use net_traits::image_cache::{CanRequestImages, ImageCache, ImageOrMetadataAvailable};
@@ -61,6 +62,7 @@ use net_traits::request::RequestBuilder;
 use net_traits::{FetchMetadata, FetchResponseListener, FetchResponseMsg, NetworkError};
 use net_traits::{ResourceFetchTiming, ResourceTimingType};
 use num_traits::ToPrimitive;
+use servo_url::origin::ImmutableOrigin;
 use servo_url::origin::MutableOrigin;
 use servo_url::ServoUrl;
 use std::cell::{Cell, RefMut};
@@ -261,6 +263,17 @@ impl PreInvoke for ImageContext {
     }
 }
 
+// This function is also used to prefetch an image in `script::dom::servoparser::prefetch`.
+pub(crate) fn image_fetch_request(
+    img_url: ServoUrl,
+    origin: ImmutableOrigin,
+    pipeline_id: PipelineId,
+) -> RequestBuilder {
+    RequestBuilder::new(img_url)
+        .origin(origin)
+        .pipeline_id(Some(pipeline_id))
+}
+
 impl HTMLImageElement {
     /// Update the current image with a valid URL.
     fn fetch_image(&self, img_url: &ServoUrl) {
@@ -326,9 +339,11 @@ impl HTMLImageElement {
             }),
         );
 
-        let request = RequestBuilder::new(img_url.clone())
-            .origin(document.origin().immutable().clone())
-            .pipeline_id(Some(document.global().pipeline_id()));
+        let request = image_fetch_request(
+            img_url.clone(),
+            document.origin().immutable().clone(),
+            document.global().pipeline_id(),
+        );
 
         // This is a background load because the load blocker already fulfills the
         // purpose of delaying the document's load event.

components/script/dom/htmlscriptelement.rs

@@ -32,12 +32,15 @@ use html5ever::{LocalName, Prefix};
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
 use js::jsval::UndefinedValue;
+use msg::constellation_msg::PipelineId;
 use net_traits::request::{
     CorsSettings, CredentialsMode, Destination, Referrer, RequestBuilder, RequestMode,
 };
+use net_traits::ReferrerPolicy;
 use net_traits::{FetchMetadata, FetchResponseListener, Metadata, NetworkError};
 use net_traits::{ResourceFetchTiming, ResourceTimingType};
 use servo_atoms::Atom;
+use servo_url::ImmutableOrigin;
 use servo_url::ServoUrl;
 use std::cell::Cell;
 use std::fs::File;
@@ -292,19 +295,18 @@ impl ResourceTimingListener for ClassicContext {
 
 impl PreInvoke for ClassicContext {}
 
-/// <https://html.spec.whatwg.org/multipage/#fetch-a-classic-script>
-fn fetch_a_classic_script(
-    script: &HTMLScriptElement,
-    kind: ExternalScriptKind,
+/// Steps 1-2 of <https://html.spec.whatwg.org/multipage/#fetch-a-classic-script>
+// This function is also used to prefetch a script in `script::dom::servoparser::prefetch`.
+pub(crate) fn script_fetch_request(
     url: ServoUrl,
     cors_setting: Option<CorsSettings>,
+    origin: ImmutableOrigin,
+    pipeline_id: PipelineId,
+    referrer: Referrer,
+    referrer_policy: Option<ReferrerPolicy>,
     integrity_metadata: String,
-    character_encoding: &'static Encoding,
-) {
-    let doc = document_from_node(script);
-
-    // Step 1, 2.
-    let request = RequestBuilder::new(url.clone())
+) -> RequestBuilder {
+    RequestBuilder::new(url)
         .destination(Destination::Script)
         // https://html.spec.whatwg.org/multipage/#create-a-potential-cors-request
         // Step 1
@@ -318,11 +320,34 @@ fn fetch_a_classic_script(
             Some(CorsSettings::Anonymous) => CredentialsMode::CredentialsSameOrigin,
             _ => CredentialsMode::Include,
         })
-        .origin(doc.origin().immutable().clone())
-        .pipeline_id(Some(script.global().pipeline_id()))
-        .referrer(Some(Referrer::ReferrerUrl(doc.url())))
-        .referrer_policy(doc.get_referrer_policy())
-        .integrity_metadata(integrity_metadata);
+        .origin(origin)
+        .pipeline_id(Some(pipeline_id))
+        .referrer(Some(referrer))
+        .referrer_policy(referrer_policy)
+        .integrity_metadata(integrity_metadata)
+}
+
+/// <https://html.spec.whatwg.org/multipage/#fetch-a-classic-script>
+fn fetch_a_classic_script(
+    script: &HTMLScriptElement,
+    kind: ExternalScriptKind,
+    url: ServoUrl,
+    cors_setting: Option<CorsSettings>,
+    integrity_metadata: String,
+    character_encoding: &'static Encoding,
+) {
+    let doc = document_from_node(script);
+
+    // Step 1, 2.
+    let request = script_fetch_request(
+        url.clone(),
+        cors_setting,
+        doc.origin().immutable().clone(),
+        script.global().pipeline_id(),
+        Referrer::ReferrerUrl(doc.url()),
+        doc.get_referrer_policy(),
+        integrity_metadata,
+    );
 
     // TODO: Step 3, Add custom steps to perform fetch
 

components/script/dom/servoparser/mod.rs

@@ -62,6 +62,7 @@ use tendril::stream::LossyDecoder;
 
 mod async_html;
 mod html;
+mod prefetch;
 mod xml;
 
 #[dom_struct]
@@ -101,6 +102,10 @@ pub struct ServoParser {
     aborted: Cell<bool>,
     /// <https://html.spec.whatwg.org/multipage/#script-created-parser>
     script_created_parser: bool,
+    /// We do a quick-and-dirty parse of the input looking for resources to prefetch
+    prefetch_tokenizer: DomRefCell<prefetch::Tokenizer>,
+    #[ignore_malloc_size_of = "Defined in html5ever"]
+    prefetch_input: DomRefCell<BufferQueue>,
 }
 
 #[derive(PartialEq)]
@@ -403,6 +408,8 @@ impl ServoParser {
             script_nesting_level: Default::default(),
             aborted: Default::default(),
             script_created_parser: kind == ParserKind::ScriptCreated,
+            prefetch_tokenizer: DomRefCell::new(prefetch::Tokenizer::new(document)),
+            prefetch_input: DomRefCell::new(BufferQueue::new()),
         }
     }
 
@@ -425,20 +432,50 @@ impl ServoParser {
         )
     }
 
+    fn push_tendril_input_chunk(&self, chunk: StrTendril) {
+        if !chunk.is_empty() {
+            // Per https://github.com/whatwg/html/issues/1495
+            // stylesheets should not be loaded for documents
+            // without browsing contexts.
+            // https://github.com/whatwg/html/issues/1495#issuecomment-230334047
+            // suggests that no content should be preloaded in such a case.
+            // We're conservative, and only prefetch for documents
+            // with browsing contexts.
+            if self.document.browsing_context().is_some() {
+                // Push the chunk into the prefetch input stream,
+                // which is tokenized eagerly, to scan for resources
+                // to prefetch. If the user script uses `document.write()`
+                // to overwrite the network input, this prefetching may
+                // have been wasted, but in most cases it won't.
+                let mut prefetch_input = self.prefetch_input.borrow_mut();
+                prefetch_input.push_back(chunk.clone());
+                let _ = self.prefetch_tokenizer
+                    .borrow_mut()
+                    .feed(&mut *prefetch_input);
+            }
+            // Push the chunk into the network input stream,
+            // which is tokenized lazily.
+            self.network_input.borrow_mut().push_back(chunk);
+        }
+    }
+
     fn push_bytes_input_chunk(&self, chunk: Vec<u8>) {
+        // For byte input, we convert it to text using the network decoder.
         let chunk = self
             .network_decoder
             .borrow_mut()
             .as_mut()
             .unwrap()
             .decode(chunk);
-        if !chunk.is_empty() {
-            self.network_input.borrow_mut().push_back(chunk);
-        }
+        self.push_tendril_input_chunk(chunk);
     }
 
     fn push_string_input_chunk(&self, chunk: String) {
-        self.network_input.borrow_mut().push_back(chunk.into());
+        // Convert the chunk to a tendril so cloning it isn't expensive.
+        // The input has already been decoded as a string, so doesn't need
+        // to be decoded by the network decoder again.
+        let chunk = StrTendril::from(chunk);
+        self.push_tendril_input_chunk(chunk);
     }
 
     fn parse_sync(&self) {

components/script/dom/servoparser/prefetch.rs

@@ -0,0 +1,185 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+use crate::dom::bindings::reflector::DomObject;
+use crate::dom::bindings::trace::JSTraceable;
+use crate::dom::document::Document;
+use crate::dom::htmlimageelement::image_fetch_request;
+use crate::dom::htmlscriptelement::script_fetch_request;
+use crate::stylesheet_loader::stylesheet_fetch_request;
+use html5ever::buffer_queue::BufferQueue;
+use html5ever::tokenizer::Tag;
+use html5ever::tokenizer::TagKind;
+use html5ever::tokenizer::Token;
+use html5ever::tokenizer::TokenSink;
+use html5ever::tokenizer::TokenSinkResult;
+use html5ever::tokenizer::Tokenizer as HtmlTokenizer;
+use html5ever::tokenizer::TokenizerResult;
+use html5ever::Attribute;
+use html5ever::LocalName;
+use js::jsapi::JSTracer;
+use msg::constellation_msg::PipelineId;
+use net_traits::request::CorsSettings;
+use net_traits::request::Referrer;
+use net_traits::CoreResourceMsg;
+use net_traits::FetchChannels;
+use net_traits::IpcSend;
+use net_traits::ReferrerPolicy;
+use net_traits::ResourceThreads;
+use servo_url::ImmutableOrigin;
+use servo_url::ServoUrl;
+
+#[derive(JSTraceable, MallocSizeOf)]
+#[must_root]
+pub struct Tokenizer {
+    #[ignore_malloc_size_of = "Defined in html5ever"]
+    inner: HtmlTokenizer<PrefetchSink>,
+}
+
+#[allow(unsafe_code)]
+unsafe impl JSTraceable for HtmlTokenizer<PrefetchSink> {
+    unsafe fn trace(&self, trc: *mut JSTracer) {
+        self.sink.trace(trc)
+    }
+}
+
+impl Tokenizer {
+    pub fn new(document: &Document) -> Self {
+        let sink = PrefetchSink {
+            origin: document.origin().immutable().clone(),
+            pipeline_id: document.global().pipeline_id(),
+            base: document.url(),
+            referrer: Referrer::ReferrerUrl(document.url()),
+            referrer_policy: document.get_referrer_policy(),
+            resource_threads: document.loader().resource_threads().clone(),
+            // Initially we set prefetching to false, and only set it
+            // true after the first script tag, since that is what will
+            // block the main parser.
+            prefetching: false,
+        };
+        let options = Default::default();
+        let inner = HtmlTokenizer::new(sink, options);
+        Tokenizer { inner }
+    }
+
+    pub fn feed(&mut self, input: &mut BufferQueue) -> TokenizerResult<()> {
+        self.inner.feed(input)
+    }
+}
+
+#[derive(JSTraceable)]
+struct PrefetchSink {
+    origin: ImmutableOrigin,
+    pipeline_id: PipelineId,
+    base: ServoUrl,
+    referrer: Referrer,
+    referrer_policy: Option<ReferrerPolicy>,
+    resource_threads: ResourceThreads,
+    prefetching: bool,
+}
+
+impl TokenSink for PrefetchSink {
+    type Handle = ();
+    fn process_token(&mut self, token: Token, _line_number: u64) -> TokenSinkResult<()> {
+        if let Token::TagToken(ref tag) = token {
+            match (tag.kind, &tag.name) {
+                (TagKind::StartTag, local_name!("script")) if self.prefetching => {
+                    if let Some(url) = self.get_url(tag, local_name!("src")) {
+                        debug!("Prefetch script {}", url);
+                        let cors_setting = self.get_cors_settings(tag, local_name!("crossorigin"));
+                        let integrity_metadata = self
+                            .get_attr(tag, local_name!("integrity"))
+                            .map(|attr| String::from(&attr.value))
+                            .unwrap_or_default();
+                        let request = script_fetch_request(
+                            url,
+                            cors_setting,
+                            self.origin.clone(),
+                            self.pipeline_id,
+                            self.referrer.clone(),
+                            self.referrer_policy,
+                            integrity_metadata,
+                        );
+                        let _ = self
+                            .resource_threads
+                            .send(CoreResourceMsg::Fetch(request, FetchChannels::Prefetch));
+                    }
+                    // Don't prefetch inside script
+                    self.prefetching = false;
+                },
+                (TagKind::StartTag, local_name!("img")) if self.prefetching => {
+                    if let Some(url) = self.get_url(tag, local_name!("src")) {
+                        debug!("Prefetch {} {}", tag.name, url);
+                        let request =
+                            image_fetch_request(url, self.origin.clone(), self.pipeline_id);
+                        let _ = self
+                            .resource_threads
+                            .send(CoreResourceMsg::Fetch(request, FetchChannels::Prefetch));
+                    }
+                },
+                (TagKind::StartTag, local_name!("link")) if self.prefetching => {
+                    if let Some(rel) = self.get_attr(tag, local_name!("rel")) {
+                        if rel.value.eq_ignore_ascii_case("stylesheet") {
+                            if let Some(url) = self.get_url(tag, local_name!("href")) {
+                                debug!("Prefetch {} {}", tag.name, url);
+                                let cors_setting =
+                                    self.get_cors_settings(tag, local_name!("crossorigin"));
+                                let integrity_metadata = self
+                                    .get_attr(tag, local_name!("integrity"))
+                                    .map(|attr| String::from(&attr.value))
+                                    .unwrap_or_default();
+                                let request = stylesheet_fetch_request(
+                                    url,
+                                    cors_setting,
+                                    self.origin.clone(),
+                                    self.pipeline_id,
+                                    self.referrer.clone(),
+                                    self.referrer_policy,
+                                    integrity_metadata,
+                                );
+                                let _ = self
+                                    .resource_threads
+                                    .send(CoreResourceMsg::Fetch(request, FetchChannels::Prefetch));
+                            }
+                        }
+                    }
+                },
+                (TagKind::EndTag, local_name!("script")) => {
+                    // After the first script tag, the main parser is blocked, so it's worth prefetching.
+                    self.prefetching = true;
+                },
+                (TagKind::StartTag, local_name!("base")) => {
+                    if let Some(url) = self.get_url(tag, local_name!("href")) {
+                        debug!("Setting base {}", url);
+                        self.base = url;
+                    }
+                },
+                _ => {},
+            }
+        }
+        TokenSinkResult::Continue
+    }
+}
+
+impl PrefetchSink {
+    fn get_attr<'a>(&'a self, tag: &'a Tag, name: LocalName) -> Option<&'a Attribute> {
+        tag.attrs.iter().find(|attr| attr.name.local == name)
+    }
+
+    fn get_url(&self, tag: &Tag, name: LocalName) -> Option<ServoUrl> {
+        self.get_attr(tag, name)
+            .and_then(|attr| ServoUrl::parse_with_base(Some(&self.base), &attr.value).ok())
+    }
+
+    fn get_cors_settings(&self, tag: &Tag, name: LocalName) -> Option<CorsSettings> {
+        let crossorigin = self.get_attr(tag, name)?;
+        if crossorigin.value.eq_ignore_ascii_case("anonymous") {
+            Some(CorsSettings::Anonymous)
+        } else if crossorigin.value.eq_ignore_ascii_case("use-credentials") {
+            Some(CorsSettings::UseCredentials)
+        } else {
+            None
+        }
+    }
+}

components/script/stylesheet_loader.rs

@@ -22,6 +22,7 @@ use encoding_rs::UTF_8;
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
 use mime::{self, Mime};
+use msg::constellation_msg::PipelineId;
 use net_traits::request::{
     CorsSettings, CredentialsMode, Destination, Referrer, RequestBuilder, RequestMode,
 };
@@ -31,6 +32,7 @@ use net_traits::{
 use net_traits::{ResourceFetchTiming, ResourceTimingType};
 use parking_lot::RwLock;
 use servo_arc::Arc;
+use servo_url::ImmutableOrigin;
 use servo_url::ServoUrl;
 use std::mem;
 use std::sync::atomic::AtomicBool;
@@ -318,30 +320,51 @@ impl<'a> StylesheetLoader<'a> {
             document.increment_script_blocking_stylesheet_count();
         }
 
-        let request = RequestBuilder::new(url.clone())
-            .destination(Destination::Style)
-            // https://html.spec.whatwg.org/multipage/#create-a-potential-cors-request
-            // Step 1
-            .mode(match cors_setting {
-                Some(_) => RequestMode::CorsMode,
-                None => RequestMode::NoCors,
-            })
-            // https://html.spec.whatwg.org/multipage/#create-a-potential-cors-request
-            // Step 3-4
-            .credentials_mode(match cors_setting {
-                Some(CorsSettings::Anonymous) => CredentialsMode::CredentialsSameOrigin,
-                _ => CredentialsMode::Include,
-            })
-            .origin(document.origin().immutable().clone())
-            .pipeline_id(Some(self.elem.global().pipeline_id()))
-            .referrer(Some(Referrer::ReferrerUrl(document.url())))
-            .referrer_policy(referrer_policy)
-            .integrity_metadata(integrity_metadata);
+        let request = stylesheet_fetch_request(
+            url.clone(),
+            cors_setting,
+            document.origin().immutable().clone(),
+            self.elem.global().pipeline_id(),
+            Referrer::ReferrerUrl(document.url()),
+            referrer_policy,
+            integrity_metadata,
+        );
 
         document.fetch_async(LoadType::Stylesheet(url), request, action_sender);
     }
 }
 
+// This function is also used to prefetch a stylesheet in `script::dom::servoparser::prefetch`.
+pub(crate) fn stylesheet_fetch_request(
+    url: ServoUrl,
+    cors_setting: Option<CorsSettings>,
+    origin: ImmutableOrigin,
+    pipeline_id: PipelineId,
+    referrer: Referrer,
+    referrer_policy: Option<ReferrerPolicy>,
+    integrity_metadata: String,
+) -> RequestBuilder {
+    RequestBuilder::new(url)
+        .destination(Destination::Style)
+        // https://html.spec.whatwg.org/multipage/#create-a-potential-cors-request
+        // Step 1
+        .mode(match cors_setting {
+            Some(_) => RequestMode::CorsMode,
+            None => RequestMode::NoCors,
+        })
+        // https://html.spec.whatwg.org/multipage/#create-a-potential-cors-request
+        // Step 3-4
+        .credentials_mode(match cors_setting {
+            Some(CorsSettings::Anonymous) => CredentialsMode::CredentialsSameOrigin,
+            _ => CredentialsMode::Include,
+        })
+        .origin(origin)
+        .pipeline_id(Some(pipeline_id))
+        .referrer(Some(referrer))
+        .referrer_policy(referrer_policy)
+        .integrity_metadata(integrity_metadata)
+}
+
 impl<'a> StyleStylesheetLoader for StylesheetLoader<'a> {
     /// Request a stylesheet after parsing a given `@import` rule, and return
     /// the constructed `@import` rule.