at_exit.h - mozsearch

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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: */

// Copyright (c) 2006-2008 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.

#ifndef BASE_AT_EXIT_H_

#define BASE_AT_EXIT_H_

#include <stack>

#include "base/basictypes.h"

#include "mozilla/Mutex.h"

namespace base {

// This class provides a facility similar to the CRT atexit(), except that

// we control when the callbacks are executed. Under Windows for a DLL they

// happen at a really bad time and under the loader lock. This facility is

// mostly used by base::Singleton.

//

// The usage is simple. Early in the main() or WinMain() scope create an

// AtExitManager object on the stack:

// int main(...) {

//    base::AtExitManager exit_manager;

//

// }

// When the exit_manager object goes out of scope, all the registered

// callbacks and singleton destructors will be called.

class AtExitManager {

 protected:

  // This constructor will allow this instance of AtExitManager to be created

  // even if one already exists.  This should only be used for testing!

  // AtExitManagers are kept on a global stack, and it will be removed during

  // destruction.  This allows you to shadow another AtExitManager.

  explicit AtExitManager(bool shadow);

 public:

  typedef void (*AtExitCallbackType)(void*);

  AtExitManager();

  // The dtor calls all the registered callbacks. Do not try to register more

  // callbacks after this point.

  ~AtExitManager();

  // Registers the specified function to be called at exit. The prototype of

  // the callback function is void func().

  static void RegisterCallback(AtExitCallbackType func, void* param);

  // Calls the functions registered with RegisterCallback in LIFO order. It

  // is possible to register new callbacks after calling this function.

  static void ProcessCallbacksNow();

  static bool AlreadyRegistered();

 private:

  struct CallbackAndParam {

    CallbackAndParam(AtExitCallbackType func, void* param)

        : func_(func), param_(param) {}

    AtExitCallbackType func_;

    void* param_;

};

  mozilla::Mutex lock_;

  std::stack<CallbackAndParam> stack_ MOZ_GUARDED_BY(lock_);

  AtExitManager* next_manager_;  // Stack of managers to allow shadowing.

  DISALLOW_COPY_AND_ASSIGN(AtExitManager);

};

}  // namespace base

#endif  // BASE_AT_EXIT_H_