gecko-dev/netwerk/base/AutoClose.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=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 mozilla_net_AutoClose_h
#define mozilla_net_AutoClose_h

#include "nsCOMPtr.h"
#include "mozilla/Mutex.h"

namespace mozilla {
namespace net {

// Like an nsAutoPtr for XPCOM streams (e.g. nsIAsyncInputStream) and other
// refcounted classes that need to have the Close() method called explicitly
// before they are destroyed.
template <typename T>
class AutoClose {
 public:
  AutoClose() : mMutex("net::AutoClose.mMutex") {}
  ~AutoClose() { CloseAndRelease(); }

  explicit operator bool() {
    MutexAutoLock lock(mMutex);
    return mPtr;
  }

  already_AddRefed<T> forget() {
    MutexAutoLock lock(mMutex);
    return mPtr.forget();
  }

  void takeOver(nsCOMPtr<T> &rhs) { TakeOverInternal(rhs.forget()); }

  void CloseAndRelease() { TakeOverInternal(nullptr); }

 private:
  void TakeOverInternal(already_AddRefed<T> &&aOther) {
    nsCOMPtr<T> ptr(std::move(aOther));
    {
      MutexAutoLock lock(mMutex);
      ptr.swap(mPtr);
    }

    if (ptr) {
      ptr->Close();
    }
  }

  void operator=(const AutoClose<T> &) = delete;
  AutoClose(const AutoClose<T> &) = delete;

  nsCOMPtr<T> mPtr;
  Mutex mMutex;
};

}  // namespace net
}  // namespace mozilla

#endif  // mozilla_net_AutoClose_h