Keep only base/extractor.[cc|h].

base/singleton.h

-// Copyright 2004-2009 Google Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-// ========================================================================
-//
-// Defines two classes
-// 1. class SingletonBase.
-// 2. template class Singleton.
-// Creation of singletons is a common
-// activity. Use Singleton class to not
-// repeat code every time.
-
-#ifndef OMAHA_COMMON_SINGLETON_H_
-#define OMAHA_COMMON_SINGLETON_H_
-
-#include "omaha/base/debug.h"
-#include "omaha/base/synchronized.h"
-
-
-// Very important design pattern.
-// Singleton class can be used in two ways.
-// 1. Pass the class you want to make into Singleton as a
-//    template parameter.
-//
-//    class SomeClass {
-//     protected:
-//    SomeClass(){}  // note - it is protected
-//    ~SomeClass(){} // note - it is protected
-//    public:
-//    void Foo() {}
-//  };
-//
-//   Singleton<SomeClass> s;
-//   s::Instance()->Foo();
-//
-//     OR
-// 2. You class can be derived from Singleton in a following way:
-//    class SomeClass : public Singleton<SomeClass> {
-//     protected:
-//    SomeClass(){}
-//    ~SomeClass(){}
-//    public:
-//    void Foo() {}
-//  };
-//
-//   SomeClass::Instance()->Foo();
-//
-//  There is no requirement on the class you want to make into
-//  Singleton except is has to have constructor that takes nothing.
-//  As long as the class has void constructor it can become a singleton.
-//  However if you want you class to be trully singleton you have to make
-//  it constructors and destructors protected. Than you can only access your
-//  class through the singlenot interface Instance().
-//  If simple void constructor is not enough for you class, provide some kind of
-//  initialization function, which could be called after the instance is
-// created.
-
-#define kSingletonMutexName               kLockPrefix L"Singleton_Creation_Lock"
-
-#ifdef _DEBUG
-  #define InstanceReturnTypeDeclaration SingletonProxy<T>
-  #define InstanceReturnTypeStatement   SingletonProxy<T>
-#else
-  #define InstanceReturnTypeDeclaration T*
-  #define InstanceReturnTypeStatement
-#endif
-
-template <typename T> class Singleton  {
-  // Caching pointers to Singletons is very dangerous and goes against
-  // Singleton philosophy. So we will return proxy from instance in Debug mode.
-  // In release mode we will not go this route for efficiency.
-  template <typename T> class SingletonProxy {
-    T* data_;
-  public:
-    explicit SingletonProxy(T* data) : data_(data) {}
-    T* operator->() const  {
-      return data_;
-    }
-    SingletonProxy& operator=(const SingletonProxy&);
-  };
-
- public:
-  Singleton() {}
-
-  // Use double-check pattern for efficiency.
-  // TODO(omaha): the pattern is broken on multicore.
-  static InstanceReturnTypeDeclaration Instance() {
-    if(instance_ == NULL) {
-      // We use GLock here since LLock will not give us synchronization and
-      // SimpleLock will create deadlock if one singleton is created in the
-      // constructor of the other singleton.
-      GLock creation_lock;
-      TCHAR mutex_name[MAX_PATH] = {0};
-      wsprintf(mutex_name, L"%s%d",
-               kSingletonMutexName, ::GetCurrentProcessId());
-
-      VERIFY1(creation_lock.Initialize(mutex_name));
-      __mutexScope(creation_lock);
-      if(instance_ == NULL)
-         instance_ = GetInstance();
-    }
-    return InstanceReturnTypeStatement(instance_);
-  }
-
- private:
-  static T* GetInstance() {
-    static MyT my_t;
-    return &my_t;
-  }
-
-  // shared between the same type T.
-  static T * instance_;
-
-  // Needed to access the protected constructor
-  // of a client.
-  class MyT : public T {
-  };
-};
-
-// This instance_ is shared between template of the same type.
-template <typename T>  T* Singleton<T>::instance_ = NULL;
-
-#endif  // OMAHA_COMMON_SINGLETON_H_