**** [WIP] Blink-side: Implement FetchBlobDataConsumerHandle ****

Source/modules/fetch/FetchBlobDataConsumerHandle.cpp

+// Copyright 2015 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.
+
+#include "config.h"
+#include "modules/fetch/FetchBlobDataConsumerHandle.h"
+
+#include "core/dom/ActiveDOMObject.h"
+#include "core/dom/CrossThreadTask.h"
+#include "core/dom/ExecutionContext.h"
+#include "core/fetch/FetchInitiatorTypeNames.h"
+#include "core/loader/ThreadableLoaderClient.h"
+#include "modules/fetch/CompositeDataConsumerHandle.h"
+#include "modules/fetch/DataConsumerHandleUtil.h"
+#include "platform/Task.h"
+#include "platform/blob/BlobRegistry.h"
+#include "platform/blob/BlobURL.h"
+#include "platform/network/ResourceRequest.h"
+#include "public/platform/Platform.h"
+#include "public/platform/WebTraceLocation.h"
+#include "wtf/Locker.h"
+#include "wtf/ThreadingPrimitives.h"
+
+namespace blink {
+
+using Result = FetchBlobDataConsumerHandle::Result;
+
+namespace {
+
+// CrossThreadHolder<T> provides cross-thread access to |obj| of class T.
+// CrossThreadHolder<T> can be passed across threads while |obj|'s methods
+// are called on the fixed thread of |executionContext| via
+// CrossThreadHolder<T>::postTask().
+// |obj| is destructed when |executionContext| is stopped or
+// CrossThreadHolder is destructed (earlier of them).
+template<typename T>
+class CrossThreadHolder {
+public:
+    static PassOwnPtr<CrossThreadHolder<T>> create(ExecutionContext* executionContext, PassOwnPtr<T> obj)
+    {
+        return adoptPtr(new CrossThreadHolder(executionContext, obj));
+    }
+
+    // Can be called from any thread.
+    // Executes |task| with |obj| and |executionContext| on the thread of
+    // |executionContext|.
+    // NOTE: |task| might be silently ignored (i.e. not executed) when
+    // |executionContext| is stopped.
+    void postTask(PassOwnPtr<WTF::Function<void(T*, ExecutionContext*)>> task)
+    {
+        m_peer->postTask(task);
+    }
+
+    ~CrossThreadHolder()
+    {
+        m_peer->clear();
+    }
+
+private:
+    CrossThreadHolder(ExecutionContext* executionContext, PassOwnPtr<T> obj)
+        : m_peer(adoptRef(new Peer()))
+    {
+        m_peer->initialize(new Bridge(executionContext, m_peer, obj));
+    }
+
+    // Bridge and Peer have a reference cycle:
+    //     T <-OwnPtr- |Bridge| ---------RefPtr--------> |Peer| <-(RefPtr)- CTH
+    //                 |      | <-CrossThreadPersistent- |    |
+    //     CTH: CrossThreadHolder<T>
+    // The reference from Peer to Bridge is protected by |Peer::m_mutex| and
+    // cleared when Peer::clear() is called, i.e.:
+    // [1] when |executionContext| is stopped:
+    //     T <-OwnPtr- |Bridge| ---------RefPtr--------> |Peer| <-(RefPtr)- CTH
+    // [2] or when CrossThreadHolder is destructed:
+    //     T <-OwnPtr- |Bridge| ---------RefPtr--------> |Peer|
+    // in either case, Bridge is shortly garbage collected.
+
+    class Peer;
+
+    // All methods must be called on |executionContext|'s thread.
+    class Bridge
+        : public GarbageCollectedFinalized<Bridge>
+        , public ActiveDOMObject {
+        WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Bridge);
+    public:
+        Bridge(ExecutionContext* executionContext, PassRefPtr<Peer> peer, PassOwnPtr<T> obj)
+            : ActiveDOMObject(executionContext)
+            , m_peer(peer)
+            , m_obj(obj)
+        {
+            suspendIfNeeded();
+        }
+
+        DEFINE_INLINE_TRACE()
+        {
+            visitor->trace(m_obj);
+            ActiveDOMObject::trace(visitor);
+        }
+
+        T* getObject() const { return m_obj.get(); }
+
+    private:
+        // ActiveDOMObject
+        void stop() override
+        {
+            ASSERT(executionContext()->isContextThread());
+            m_obj.clear();
+            m_peer->clear();
+        }
+
+        RefPtr<Peer> m_peer;
+        OwnPtr<T> m_obj;
+    };
+
+    class Peer : public ThreadSafeRefCounted<Peer> {
+    public:
+        // initialize() must be called only just after construction to create a
+        // reference cycle.
+        void initialize(Bridge* bridge)
+        {
+            m_bridge = bridge;
+        }
+
+        void clear()
+        {
+            MutexLocker locker(m_mutex);
+            m_bridge.clear();
+        }
+
+        void postTask(PassOwnPtr<WTF::Function<void(T*, ExecutionContext*)>> task)
+        {
+            MutexLocker locker(m_mutex);
+            if (!m_bridge) {
+                // The bridge has already disappeared.
+                return;
+            }
+            m_bridge->executionContext()->postTask(FROM_HERE, createCrossThreadTask(&Peer::runTask, this, task));
+        }
+
+    private:
+        // Must be called on the loader thread.
+        void runTask(PassOwnPtr<WTF::Function<void(T*, ExecutionContext*)>> task)
+        {
+            Bridge* bridge;
+            {
+                MutexLocker locker(m_mutex);
+                bridge = m_bridge.get();
+                if (!bridge) {
+                    // LoaderContext has already disappeared.
+                    return;
+                }
+                ASSERT(bridge->executionContext()->isContextThread());
+            }
+
+            // |bridge| can be set to nullptr by another thread after the
+            // mutex is unlocked, but we can still use |loaderContext| here because
+            // the LoaderContext belongs to the current thread (== the loader thread).
+            (*task)(bridge->getObject(), bridge->executionContext());
+        }
+
+        // |m_brige| is protected by |m_mutex|.
+        CrossThreadPersistent<Bridge> m_bridge;
+        Mutex m_mutex;
+    };
+
+    RefPtr<Peer> m_peer;
+};
+
+// LoaderContext and associated ThreadableLoader is created and
+// destructed on the same thread (call this thread loader thread).
+// All methods must be called on the loader thread.
+// CommonContext and LoaderContext have a reference cycle:
+//     CTH <-----(OwnPtr)----+
+//     |                     |
+//   (CrossThreadPersistent) |
+//     v                     |
+//     LC ----(RefPtr)----> CC <-- RC
+//         LC: LoaderContext
+//         CC: CommonContext
+//         RC: ReaderContext
+//         CTH: CrossThreadHolder<LoaderContext>
+// This cycle is broken when CommonContext::clearLoaderContext() is called
+// (which clears the reference to CrossThreadHolder),
+// or ExecutionContext of the loader thread is stopped
+// (CrossThreadHolder clears the reference to LoaderContext).
+
+class LoaderContext {
+public:
+    virtual ~LoaderContext() { }
+    virtual void start(ExecutionContext*) = 0;
+};
+
+class CommonContext
+    : public ThreadSafeRefCounted<CommonContext> {
+public:
+    CommonContext()
+        : m_handle(CompositeDataConsumerHandle::create(createWaitingDataConsumerHandle())) { }
+
+    // initialize() must be called only just after construction to create a
+    // reference cycle.
+    void initialize(ExecutionContext* executionContext, PassOwnPtr<LoaderContext> loaderContext)
+    {
+        m_loaderContextHolder = CrossThreadHolder<LoaderContext>::create(executionContext, loaderContext);
+    }
+
+    CompositeDataConsumerHandle* handle() { return m_handle.get(); }
+
+    void startLoader()
+    {
+        MutexLocker locker(m_mutex);
+        if (m_loaderContextHolder)
+            m_loaderContextHolder->postTask(threadSafeBind<LoaderContext*, ExecutionContext*>(&LoaderContext::start));
+    }
+
+    void clearLoaderContext()
+    {
+        MutexLocker locker(m_mutex);
+        m_loaderContextHolder.clear();
+    }
+
+    // Must be called on the loader thread.
+    void error()
+    {
+        clearLoaderContext();
+        handle()->update(createUnexpectedErrorDataConsumerHandle());
+    }
+
+private:
+    OwnPtr<CompositeDataConsumerHandle> m_handle;
+
+    // |m_loaderContextHolder| is protected by |m_mutex|.
+    OwnPtr<CrossThreadHolder<LoaderContext>> m_loaderContextHolder;
+    Mutex m_mutex;
+};
+
+// All methods must be called on the loader thread.
+// This class is not final for testing.
+class BlobLoaderContext
+    : public LoaderContext
+    , public ThreadableLoaderClient {
+    WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(LoaderContext);
+public:
+    BlobLoaderContext(PassRefPtr<CommonContext> commonContext, PassRefPtr<BlobDataHandle> blobDataHandle, FetchBlobDataConsumerHandle::LoaderFactory* loaderFactory)
+        : m_commonContext(commonContext)
+        , m_blobDataHandle(blobDataHandle)
+        , m_loaderFactory(loaderFactory)
+        , m_receivedResponse(false) { }
+
+    ~BlobLoaderContext() override
+    {
+        if (m_loader && !m_receivedResponse)
+            m_commonContext->handle()->update(createUnexpectedErrorDataConsumerHandle());
+        if (m_loader) {
+            m_loader->cancel();
+            m_loader.clear();
+        }
+    }
+
+    void start(ExecutionContext* executionContext) override
+    {
+        ASSERT(executionContext->isContextThread());
+        ASSERT(!m_loader);
+
+        m_loader = createLoader(executionContext, this);
+        if (!m_loader)
+            m_commonContext->error();
+    }
+
+private:
+    virtual PassRefPtr<ThreadableLoader> createLoader(ExecutionContext* executionContext, ThreadableLoaderClient* client) const
+    {
+        KURL url = BlobURL::createPublicURL(executionContext->securityOrigin());
+        if (url.isEmpty()) {
+            return nullptr;
+        }
+        BlobRegistry::registerPublicBlobURL(executionContext->securityOrigin(), url, m_blobDataHandle);
+
+        ResourceRequest request(url);
+        request.setRequestContext(WebURLRequest::RequestContextInternal);
+        request.setUseStreamOnResponse(true);
+
+        ThreadableLoaderOptions options;
+        options.preflightPolicy = ConsiderPreflight;
+        options.crossOriginRequestPolicy = DenyCrossOriginRequests;
+        options.contentSecurityPolicyEnforcement = DoNotEnforceContentSecurityPolicy;
+        options.initiator = FetchInitiatorTypeNames::internal;
+
+        ResourceLoaderOptions resourceLoaderOptions;
+        resourceLoaderOptions.dataBufferingPolicy = DoNotBufferData;
+
+        return m_loaderFactory->create(*executionContext, client, request, options, resourceLoaderOptions);
+    }
+
+    // ThreadableLoaderClient
+    void didReceiveResponse(unsigned long, const ResourceResponse&, PassOwnPtr<WebDataConsumerHandle> handle) override
+    {
+        ASSERT(!m_receivedResponse);
+        m_receivedResponse = true;
+        if (!handle) {
+            // Here we assume WebURLLoader must return the response body as
+            // |WebDataConsumerHandle| since we call
+            // request.setUseStreamOnResponse().
+            m_commonContext->handle()->update(createUnexpectedErrorDataConsumerHandle());
+            return;
+        }
+        m_commonContext->handle()->update(handle);
+    }
+    void didFinishLoading(unsigned long, double) override
+    {
+        m_commonContext->clearLoaderContext();
+    }
+    void didFail(const ResourceError&) override
+    {
+        if (m_receivedResponse)
+            m_commonContext->clearLoaderContext();
+        else
+            m_commonContext->error();
+    }
+    void didFailRedirectCheck() override
+    {
+        if (m_receivedResponse)
+            m_commonContext->clearLoaderContext();
+        else
+            m_commonContext->error();
+    }
+
+    RefPtr<CommonContext> m_commonContext;
+    RefPtr<BlobDataHandle> m_blobDataHandle;
+    Persistent<FetchBlobDataConsumerHandle::LoaderFactory> m_loaderFactory;
+    RefPtr<ThreadableLoader> m_loader;
+
+    bool m_receivedResponse;
+};
+
+class DefaultLoaderFactory final : public FetchBlobDataConsumerHandle::LoaderFactory {
+public:
+    PassRefPtr<ThreadableLoader> create(
+        ExecutionContext& executionContext,
+        ThreadableLoaderClient* client,
+        const ResourceRequest& request,
+        const ThreadableLoaderOptions& options,
+        const ResourceLoaderOptions& resourceLoaderOptions) override
+    {
+        return ThreadableLoader::create(executionContext, client, request, options, resourceLoaderOptions);
+    }
+};
+
+} // namespace
+
+// ReaderContext is referenced from FetchBlobDataConsumerHandle and
+// FetchDataConsumerHandle::Reader.
+class FetchBlobDataConsumerHandle::ReaderContext : public ThreadSafeRefCounted<ReaderContext> {
+public:
+    class ReaderImpl : public FetchDataConsumerHandle::Reader {
+    public:
+        ReaderImpl(Client* client, PassRefPtr<ReaderContext> readerContext, PassOwnPtr<WebDataConsumerHandle::Reader> reader)
+            : m_readerContext(readerContext)
+            , m_reader(reader)
+            , m_notifier(client) { }
+        ~ReaderImpl() override { }
+
+        Result read(void* data, size_t size, Flags flags, size_t* readSize) override
+        {
+            if (m_readerContext->drained())
+                return Done;
+            m_readerContext->ensureStartLoader();
+            Result r = m_reader->read(data, size, flags, readSize);
+            if (r != ShouldWait) {
+                // We read non-empty data, so we cannot use the blob data handle which
+                // represents the whole data.
+                m_readerContext->clearBlobDataHandleForDrain();
+            }
+            return r;
+        }
+
+        Result beginRead(const void** buffer, Flags flags, size_t* available) override
+        {
+            if (m_readerContext->drained())
+                return Done;
+            m_readerContext->ensureStartLoader();
+            Result r = m_reader->beginRead(buffer, flags, available);
+            if (r != ShouldWait) {
+                // We read non-empty data, so we cannot use the blob data handle which
+                // represents the whole data.
+                m_readerContext->clearBlobDataHandleForDrain();
+            }
+            return r;
+        }
+
+        Result endRead(size_t readSize) override
+        {
+            return m_reader->endRead(readSize);
+        }
+
+        PassRefPtr<BlobDataHandle> drainAsBlobDataHandle() override
+        {
+            if (!m_readerContext->m_blobDataHandleForDrain || m_readerContext->m_blobDataHandleForDrain->size() == kuint64max)
+                return nullptr;
+            RefPtr<BlobDataHandle> blobDataHandle = m_readerContext->m_blobDataHandleForDrain;
+            m_readerContext->setDrained();
+            m_readerContext->clearBlobDataHandleForDrain();
+            return blobDataHandle.release();
+        }
+
+    private:
+        RefPtr<ReaderContext> m_readerContext;
+        OwnPtr<WebDataConsumerHandle::Reader> m_reader;
+        NotifyOnReaderCreationHelper m_notifier;
+    };
+
+    ReaderContext(ExecutionContext* executionContext, PassRefPtr<BlobDataHandle> blobDataHandle, FetchBlobDataConsumerHandle::LoaderFactory* loaderFactory)
+        : m_commonContext(adoptRef(new CommonContext()))
+        , m_loaderStarted(false)
+        , m_drained(false)
+        , m_blobDataHandleForDrain(blobDataHandle)
+    {
+        m_commonContext->initialize(executionContext, adoptPtr(new BlobLoaderContext(m_commonContext, m_blobDataHandleForDrain, loaderFactory)));
+    }
+
+    ~ReaderContext()
+    {
+        m_commonContext->clearLoaderContext();
+    }
+
+    PassOwnPtr<FetchDataConsumerHandle::Reader> obtainReader(WebDataConsumerHandle::Client* client)
+    {
+        return adoptPtr(new ReaderImpl(client, this, m_commonContext->handle()->obtainReader(client)));
+    }
+
+    void ensureStartLoader()
+    {
+        if (m_loaderStarted)
+            return;
+        m_loaderStarted = true;
+        m_commonContext->startLoader();
+    }
+
+    void clearBlobDataHandleForDrain()
+    {
+        m_blobDataHandleForDrain.clear();
+    }
+
+private:
+    bool drained() const { return m_drained; }
+    void setDrained() { m_drained = true; }
+
+    RefPtr<CommonContext> m_commonContext;
+
+    // Following members must be accessed only on the reader thread.
+    bool m_loaderStarted;
+    bool m_drained;
+    RefPtr<BlobDataHandle> m_blobDataHandleForDrain;
+};
+
+FetchBlobDataConsumerHandle::FetchBlobDataConsumerHandle(ExecutionContext* executionContext, PassRefPtr<BlobDataHandle> blobDataHandle, LoaderFactory* loaderFactory)
+    : m_readerContext(adoptRef(new ReaderContext(executionContext, blobDataHandle, loaderFactory)))
+{
+}
+
+PassOwnPtr<FetchDataConsumerHandle> FetchBlobDataConsumerHandle::create(ExecutionContext* executionContext, PassRefPtr<BlobDataHandle> blobDataHandle, LoaderFactory* loaderFactory)
+{
+    if (!blobDataHandle)
+        return createFetchDataConsumerHandleFromWebHandle(createDoneDataConsumerHandle());
+
+    return adoptPtr(new FetchBlobDataConsumerHandle(executionContext, blobDataHandle, loaderFactory));
+}
+
+PassOwnPtr<FetchDataConsumerHandle> FetchBlobDataConsumerHandle::create(ExecutionContext* executionContext, PassRefPtr<BlobDataHandle> blobDataHandle)
+{
+    if (!blobDataHandle)
+        return createFetchDataConsumerHandleFromWebHandle(createDoneDataConsumerHandle());
+
+    return adoptPtr(new FetchBlobDataConsumerHandle(executionContext, blobDataHandle, new DefaultLoaderFactory));
+}
+
+FetchDataConsumerHandle::Reader* FetchBlobDataConsumerHandle::obtainReaderInternal(Client* client)
+{
+    return m_readerContext->obtainReader(client).leakPtr();
+}
+
+} // namespace blink