third_party/WebKit/Source/core/workers/WorkerLoaderProxy.h

/*
 * Copyright (C) 2009 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
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 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#ifndef WorkerLoaderProxy_h
#define WorkerLoaderProxy_h

#include "core/CoreExport.h"
#include "core/dom/ExecutionContext.h"
#include "public/platform/WebTraceLocation.h"
#include "wtf/Forward.h"
#include "wtf/ThreadSafeRefCounted.h"

namespace blink {

// The WorkerLoaderProxy is a proxy to the loader context. Normally, the
// document on the main thread provides loading services for the subordinate
// workers. WorkerLoaderProxy provides 2-way communications to the Document
// context and back to the worker.
//
// Note that in multi-process browsers, the Worker object context and the
// Document context can be distinct.

// The abstract interface providing the methods for actually posting tasks;
// separated from the thread-safe & ref-counted WorkerLoaderProxy object which
// keeps a protected reference to the provider object. This to support
// non-overlapping lifetimes, the provider may be destructed before all
// references to the WorkerLoaderProxy object have been dropped.
//
// A provider implementation must detach itself when finalizing by calling
// WorkerLoaderProxy::detachProvider(). This stops the WorkerLoaderProxy from
// accessing the now-dead object, but it will remain alive while ref-ptrs are
// still kept to it.
class CORE_EXPORT WorkerLoaderProxyProvider {
 public:
  virtual ~WorkerLoaderProxyProvider() {}

  // Posts a task to the thread which runs the loading code (normally, the main
  // thread).
  virtual void postTaskToLoader(const WebTraceLocation&,
                                std::unique_ptr<ExecutionContextTask>) = 0;

  // Posts callbacks from loading code to the WorkerGlobalScope.
  virtual void postTaskToWorkerGlobalScope(
      const WebTraceLocation&,
      std::unique_ptr<ExecutionContextTask>) = 0;
};

class CORE_EXPORT WorkerLoaderProxy final
    : public ThreadSafeRefCounted<WorkerLoaderProxy> {
 public:
  static PassRefPtr<WorkerLoaderProxy> create(
      WorkerLoaderProxyProvider* loaderProxyProvider) {
    return adoptRef(new WorkerLoaderProxy(loaderProxyProvider));
  }

  ~WorkerLoaderProxy();

  void postTaskToLoader(const WebTraceLocation&,
                        std::unique_ptr<ExecutionContextTask>);
  void postTaskToWorkerGlobalScope(const WebTraceLocation&,
                                   std::unique_ptr<ExecutionContextTask>);

  // Notification from the provider that it can no longer be accessed. An
  // implementation of WorkerLoaderProxyProvider is required to call
  // detachProvider() when finalizing.
  void detachProvider(WorkerLoaderProxyProvider*);

 private:
  explicit WorkerLoaderProxy(WorkerLoaderProxyProvider*);

  Mutex m_lock;
  WorkerLoaderProxyProvider* m_loaderProxyProvider;
};

}  // namespace blink

#endif  // WorkerLoaderProxy_h