Prefetch img and scripts during parsing

1 files changed, 185 insertions, 0 deletions

diff --git a/components/script/dom/servoparser/prefetch.rs b/components/script/dom/servoparser/prefetch.rs
new file mode 100644
index 00000000000..314cb3b97a1
--- /dev/null
+++ b/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
+        }
+    }
+}