// Copyright (c) 2011 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 BUTIL_AT_EXIT_H_

#define BUTIL_AT_EXIT_H_

#include <stack>

#include "butil/base_export.h"

#include "butil/basictypes.h"

#include "butil/synchronization/lock.h"

namespace butil {

// 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 butil::Singleton.

//

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

// AtExitManager object on the stack:

// int main(...) {

//    butil::AtExitManager exit_manager;

//

// }

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

// callbacks and singleton destructors will be called.

class BUTIL_EXPORT AtExitManager {

 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(void*).

  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();

 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);

 private:

  struct Callback {

    AtExitCallbackType func;

    void* param;

  };

  butil::Lock lock_;

  std::stack<Callback> stack_;

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

  DISALLOW_COPY_AND_ASSIGN(AtExitManager);

};

#if defined(UNIT_TEST)

class ShadowingAtExitManager : public AtExitManager {

 public:

  ShadowingAtExitManager() : AtExitManager(true) {}

};

#endif  // defined(UNIT_TEST)

}  // namespace butil

#endif  // BUTIL_AT_EXIT_H_