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Unified Diff: base/singleton.h

Issue 624713003: Keep only base/extractor.[cc|h]. (Closed) Base URL: https://chromium.googlesource.com/external/omaha.git@master
Patch Set: Created 6 years, 2 months ago
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Index: base/singleton.h
diff --git a/base/singleton.h b/base/singleton.h
deleted file mode 100644
index fc7c043420b7a5484d7eaae4cee277672e6e661b..0000000000000000000000000000000000000000
--- a/base/singleton.h
+++ /dev/null
@@ -1,133 +0,0 @@
-// 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_
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