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 // 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 BASE_AT_EXIT_H_

 #define BASE_AT_EXIT_H_

 #include <stack>

 #include "base/base_export.h"

 #include "base/basictypes.h"

 #include "base/callback.h"

 #include "base/synchronization/lock.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 BASE_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);

   // Registers the specified task to be called at exit.

   static void RegisterTask(base::Closure task);

   // 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:

   base::Lock lock_;

   std::stack<base::Closure> 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 base

 #endif  // BASE_AT_EXIT_H_