Stream scripts to V8 as they load - Blink side.

Source/bindings/core/v8/ScriptStreamer.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ScriptStreamer_h
+#define ScriptStreamer_h
+
+#include "wtf/RefCounted.h"
+
+#include <v8.h>
+
+namespace blink {
+
+class PendingScript;
+class Resource;
+class ScriptResource;
+class ScriptResourceClient;
+class ScriptState;
+class Settings;
+class SourceStream;
+
+// ScriptStreamer streams incomplete script data to V8 so that it can be parsed
+// while it's loaded. PendingScript holds a reference to ScriptStreamer. At the
+// moment, ScriptStreamer is only used for parser blocking scripts; this means
+// that the Document stays stable and no other scripts are executing while we're
+// streaming. It is possible, though, that Document and the PendingScript are
+// destroyed while the streaming is in progress, and ScriptStreamer handles it
+// gracefully.
+class ScriptStreamer : public RefCounted<ScriptStreamer> {
+    WTF_MAKE_NONCOPYABLE(ScriptStreamer);
+public:
+    // Launches a task (on a background thread) which will stream the given
+    // PendingScript into V8 as it loads. It's also possible that V8 cannot
+    // stream the given script; in that case this function returns
+    // false. Internally, this constructs a ScriptStreamer and attaches it to
+    // the PendingScript. Use ScriptStreamer::addClient to get notified when the
+    // streaming finishes.
+    static bool startStreaming(PendingScript&, Settings*, ScriptState*);
+
+    bool streamingInProgress() const { return !m_loadingFinished || !m_parsingFinished; }
+
+    v8::ScriptCompiler::StreamedSource* source() { return &m_source; }
+    ScriptResource* resource() const { return m_resource; }
+
+    // Called when the script is not needed any more (e.g., loading was
+    // cancelled). After calling cancel, PendingScript can drop its reference to
+    // ScriptStreamer, and ScriptStreamer takes care of eventually deleting
+    // itself (after the V8 side has finished too).
+    void cancel();
+
+    // When the streaming is suppressed, the data is not given to V8, but
+    // ScriptStreamer still watches the resource load and notifies the upper
+    // layers when loading is finished. It is used in situations when we have
+    // started streaming but then we detect we don't want to stream (e.g., when
+    // we have the code cache for the script) and we still want to parse and
+    // execute it when it has finished loading.
+    void suppressStreaming() { m_streamingSuppressed = true; }
+    bool streamingSuppressed() const { return m_streamingSuppressed; }
+
+    unsigned cachedDataType() const { return m_cachedDataType; }
+
+    void addClient(ScriptResourceClient* client)
+    {
+        ASSERT(!m_client);
+        m_client = client;
+    }
+
+    void removeClient(ScriptResourceClient* client)
+    {
+        ASSERT(m_client == client);
+        m_client = 0;
+    }
+
+    // Called by PendingScript when data arrives from the network.
+    void notifyAppendData(ScriptResource*);
+    void notifyFinished(Resource*);
+
+    // Called by ScriptStreamingTask when it has streamed all data to V8 and V8
+    // has processed it.
+    void streamingComplete();
+
+private:
+    ScriptStreamer(ScriptResource*, v8::ScriptCompiler::StreamedSource::Encoding);
+
+    void notifyFinishedToClient();
+
+    // This pointer is weak. If PendingScript and its Resource are deleted
+    // before ScriptStreamer, PendingScript will notify ScriptStreamer of its
+    // deletion by calling cancel().
+    ScriptResource* m_resource;
+    // Whether ScriptStreamer is detached from the Resource. In those cases, the
+    // script data is not needed any more, and the client won't get notified
+    // when the loading and streaming are done.
+    bool m_detached;
+
+    SourceStream* m_stream;
+    v8::ScriptCompiler::StreamedSource m_source;
+    ScriptResourceClient* m_client;
+    bool m_loadingFinished; // Whether loading from the network is done.
+    bool m_parsingFinished; // Whether the V8 side processing is done.
+
+    // Whether the script source code should be retrieved from the Resource
+    // instead of the ScriptStreamer.
+    bool m_streamingSuppressed;
+
+    // What kind of cached data V8 produces during streaming.
+    unsigned m_cachedDataType;
+};
+
+} // namespace blink
+
+#endif // ScriptStreamer_h