ipc_channel_capability.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* 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 http://mozilla.org/MPL/2.0/. */

#ifndef CHROME_COMMON_IPC_CHANNEL_CAPABILITY_H_

#define CHROME_COMMON_IPC_CHANNEL_CAPABILITY_H_

#include "mozilla/ThreadSafety.h"

#include "mozilla/Mutex.h"

#include "mozilla/EventTargetCapability.h"

#include "nsISerialEventTarget.h"

namespace IPC {

// A thread-safety capability used in IPC channel implementations. Combines an

// EventTargetCapability and a Mutex to allow using each independently, as well

// as combined together.

//

// The ChannelCapability grants shared access if on the IOThread or if the send

// mutex is held, and only allows exclusive access if both on the IO thread and

// holding the send mutex. This is similar to a `MutexSingleWriter`, but more

// flexible due to providing access to each sub-capability.

class MOZ_CAPABILITY("channel cap") ChannelCapability {

 public:

  using Mutex = mozilla::Mutex;

  using Thread = mozilla::EventTargetCapability<nsISerialEventTarget>;

  ChannelCapability(const char* mutex_name, nsISerialEventTarget* io_thread)

      : send_mutex_(mutex_name), io_thread_(io_thread) {}

  const Thread& IOThread() const MOZ_RETURN_CAPABILITY(io_thread_) {

    return io_thread_;

  Mutex& SendMutex() MOZ_RETURN_CAPABILITY(send_mutex_) { return send_mutex_; }

  // Note that we're on the IO thread, and thus have shared access to values

  // guarded by the channel capability for the thread-safety analysis.

  void NoteOnIOThread() const MOZ_REQUIRES(io_thread_)

      MOZ_ASSERT_SHARED_CAPABILITY(this) {}

  // Note that we're holding the send mutex, and thus have shared access to

  // values guarded by the channel capability for the thread-safety analysis.

  void NoteSendMutex() const MOZ_REQUIRES(send_mutex_)

      MOZ_ASSERT_SHARED_CAPABILITY(this) {}

  // Note that we're holding the send mutex while on the IO thread, and thus

  // have exclusive access to values guarded by the channel capability for the

  // thread-safety analysis.

  void NoteExclusiveAccess() const MOZ_REQUIRES(io_thread_, send_mutex_)

      MOZ_ASSERT_CAPABILITY(this) {}

 private:

  mozilla::Mutex send_mutex_;

  mozilla::EventTargetCapability<nsISerialEventTarget> io_thread_;

};

}  // namespace IPC

#endif  // CHROME_COMMON_IPC_CHANNEL_CAPABILITY_H_