WorkerPool implementation for Mac, using NSOperationQueue

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@1493 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 60 insertions, 0 deletions

diff --git a/base/singleton_objc.h b/base/singleton_objc.h
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+++ b/base/singleton_objc.h
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+// Copyright (c) 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.
+
+// Support for using the Singleton<T> pattern with Objective-C objects.  A
+// SingletonObjC is the same as a Singleton, except the default traits are
+// appropriate for Objective-C objects.  A typical Objective-C object of type
+// NSExampleType can be maintained as a singleton and accessed with:
+//
+//   NSExampleType* exampleSingleton = SingletonObjC<NSExampleType>::get();
+//
+// The first time this is used, it will create exampleSingleton as the result
+// of [[NSExampleType alloc] init].  Subsequent calls will return the same
+// NSExampleType* object.  The object will be released by calling
+// -[NSExampleType release] when Singleton's atexit routines run
+// (see singleton.h).
+//
+// For Objective-C objects initialized through means other than the
+// no-parameter -init selector, DefaultSingletonObjCTraits may be extended
+// as needed:
+//
+//   struct FooSingletonTraits : public DefaultSingletonObjCTraits<Foo> {
+//     static Foo* New() {
+//       return [[Foo alloc] initWithName:@"selecty"];
+//     }
+//   }
+//   ...
+//   Foo* widgetSingleton = SingletonObjC<Foo, FooSingletonTraits>::get();
+
+#ifndef BASE_SINGLETON_OBJC_H_
+#define BASE_SINGLETON_OBJC_H_
+
+#import <Foundation/Foundation.h>
+#include "base/singleton.h"
+
+// Singleton traits usable to manage traditional Objective-C objects, which
+// are instantiated by sending |alloc| and |init| messages, and are deallocated
+// in a memory-managed environment when their retain counts drop to 0 by
+// sending |release| messages.
+template<typename Type>
+struct DefaultSingletonObjCTraits : public DefaultSingletonTraits<Type> {
+  static Type* New() {
+    return [[Type alloc] init];
+  }
+
+  static void Delete(Type* object) {
+    [object release];
+  }
+};
+
+// Exactly like Singleton, but without the DefaultSingletonObjCTraits as the
+// default trait class.  This makes it straightforward for Objective-C++ code
+// to hold Objective-C objects as singletons.
+template<typename Type,
+         typename Traits = DefaultSingletonObjCTraits<Type>,
+         typename DifferentiatingType = Type>
+class SingletonObjC : public Singleton<Type, Traits, DifferentiatingType> {
+};
+
+#endif  // BASE_SINGLETON_OBJC_H_