Source/web/WorkerFileWriterCallbacksBridge.h

/*
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 * modification, are permitted provided that the following conditions are
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 *
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 * in the documentation and/or other materials provided with the
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#ifndef WorkerFileWriterCallbacksBridge_h
#define WorkerFileWriterCallbacksBridge_h

#include "WebFileWriterClient.h"
#include "core/workers/WorkerGlobalScope.h"
#include "public/platform/WebFileError.h"
#include "wtf/PassOwnPtr.h"
#include "wtf/PassRefPtr.h"
#include "wtf/ThreadSafeRefCounted.h"

namespace WebCore {
    class AsyncFileWriterClient;
    class KURL;
    class WorkerLoaderProxy;
}

namespace WTF {
    class String;
}
using WTF::String;

namespace WebKit {

class WebFileSystem;
class WebFileWriter;
class WebFileWriterClient;
class WebURL;
class WebWorkerBase;

// This class is used as a mechanism to bridge calls between threads.
// Calls to a WebFileWriter must happen on the main thread, but they come from
// the context thread. The responses through the WebFileWriterClient interface
// start on the main thread, but must be sent via the worker context thread.
//
// A typical flow for write would look like this:
// Bridge::postWriteToMainThread() on WorkerThread
//  --> Bridge::writeOnMainThread() is called on MainThread
//  --> WebFileWriter::write()
//      This makes an IPC; the actual operation is down in the browser.
//  --> Bridge::didWrite is called on MainThread
//  --> Bridge::didWriteOnWorkerThread is called on WorkerThread
//      This calls the original client (m_clientOnWorkerThread).
//
// The bridge object is refcounted, so that it doesn't get deleted while there
// are cross-thread calls in flight. Each CrossThreadTask carries a reference
// to the bridge, which guarantees that the bridge will still be valid when the
// task is executed. In order to shut down the bridge, the WebFileWriterClient
// should call postShutdownToMainThread before dropping its reference to the
// bridge. This ensures that the WebFileWriter will be cleared on the main
// thread and that no further calls to the WebFileWriterClient will be made.
class WorkerFileWriterCallbacksBridge : public ThreadSafeRefCounted<WorkerFileWriterCallbacksBridge>, public WebCore::WorkerGlobalScope::Observer, public WebFileWriterClient {
public:
    ~WorkerFileWriterCallbacksBridge();

    // WorkerGlobalScope::Observer method.
    virtual void notifyStop();

    static PassRefPtr<WorkerFileWriterCallbacksBridge> create(const WebCore::KURL& path, WebCore::WorkerLoaderProxy* proxy, WebCore::ScriptExecutionContext* workerGlobalScope, WebCore::AsyncFileWriterClient* client)
    {
        return adoptRef(new WorkerFileWriterCallbacksBridge(path, proxy, workerGlobalScope, client));
    }

    // Methods that create an instance and post an initial request task to the main thread. They must be called on the worker thread.
    void postWriteToMainThread(long long position, const WebCore::KURL& data);
    void postTruncateToMainThread(long long length);
    void postAbortToMainThread();

    // The owning WorkerAsyncFileWriterChromium should call this method before dropping its last reference to the bridge, on the context thread.
    // The actual deletion of the WorkerFileWriterCallbacksBridge may happen on either the main or context thread, depending on where the last reference goes away; that's safe as long as this is called first.
    void postShutdownToMainThread(PassRefPtr<WorkerFileWriterCallbacksBridge>);

    // Callback methods that are called on the main thread.
    // These are the implementation of WebKit::WebFileWriterClient.
    void didWrite(long long bytes, bool complete);
    void didFail(WebFileError);
    void didTruncate();

    // Call this on the context thread to wait for the current operation to complete.
    bool waitForOperationToComplete();

private:
    WorkerFileWriterCallbacksBridge(const WebCore::KURL& path, WebCore::WorkerLoaderProxy*, WebCore::ScriptExecutionContext*, WebCore::AsyncFileWriterClient*);

    void postInitToMainThread(const WebCore::KURL& path);

    // Methods that are to be called on the main thread.
    static void writeOnMainThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>, long long position, const WebCore::KURL& data);
    static void truncateOnMainThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>, long long length);
    static void abortOnMainThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>);
    static void initOnMainThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>, const WebCore::KURL& path);
    static void shutdownOnMainThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>);

    // Methods that dispatch to AsyncFileWriterClient on the worker threads.
    static void didWriteOnWorkerThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>, long long length, bool complete);
    static void didFailOnWorkerThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>, WebFileError);
    static void didTruncateOnWorkerThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>);

    // Called on the main thread to run the supplied task.
    static void runTaskOnMainThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>, PassOwnPtr<WebCore::ScriptExecutionContext::Task>);
    // Called on the worker thread to run the supplied task.
    static void runTaskOnWorkerThread(WebCore::ScriptExecutionContext*, PassRefPtr<WorkerFileWriterCallbacksBridge>, PassOwnPtr<WebCore::ScriptExecutionContext::Task>);

    // Called on the worker thread to dispatch to the main thread.
    void dispatchTaskToMainThread(PassOwnPtr<WebCore::ScriptExecutionContext::Task>);
    // Called on the main thread to dispatch to the worker thread.
    void dispatchTaskToWorkerThread(PassOwnPtr<WebCore::ScriptExecutionContext::Task>);

    // Used from the main thread to post tasks to the context thread.
    WebCore::WorkerLoaderProxy* m_proxy;

    // Mutex for proxy.
    Mutex m_loaderProxyMutex;

    // Used on the context thread, only to check that we're running on the context thread.
    WebCore::ScriptExecutionContext* m_workerGlobalScope;

    // Created and destroyed from the main thread.
    OwnPtr<WebKit::WebFileWriter> m_writer;

    // Used on the context thread to call back into the client.
    WebCore::AsyncFileWriterClient* m_clientOnWorkerThread;

    // Used to indicate that shutdown has started on the main thread, and hence the writer has been deleted.
    bool m_writerDeleted;

    // Used by waitForOperationToComplete.
    bool m_operationInProgress;

    // Used by postTaskForModeToWorkerGlobalScope and runInMode.
    String m_mode;
};

} // namespace WebCore

#endif // WorkerFileWriterCallbacksBridge_h