Add base to the repository.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@8 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 249 insertions, 0 deletions

diff --git a/base/ref_counted.h b/base/ref_counted.h
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+++ b/base/ref_counted.h
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+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef BASE_REF_COUNTED_H__
+#define BASE_REF_COUNTED_H__
+
+#include "base/atomic.h"
+#include "base/basictypes.h"
+#include "base/logging.h"
+
+namespace base {
+
+//
+// A base class for reference counted classes.  Otherwise, known as a cheap
+// knock-off of WebKit's RefCounted<T> class.  To use this guy just extend your
+// class from it like so:
+//
+//   class MyFoo : public base::RefCounted<MyFoo> {
+//    ...
+//   };
+//
+template <class T>
+class RefCounted {
+ public:
+  RefCounted() : ref_count_(0) {
+#ifndef NDEBUG
+    in_dtor_ = false;
+#endif
+  }
+
+  ~RefCounted() {
+#ifndef NDEBUG
+    DCHECK(in_dtor_) << "RefCounted object deleted without calling Release()";
+#endif
+  }
+
+  void AddRef() {
+#ifndef NDEBUG
+    DCHECK(!in_dtor_);
+#endif
+    ++ref_count_;
+  }
+
+  void Release() {
+#ifndef NDEBUG
+    DCHECK(!in_dtor_);
+#endif
+    if (--ref_count_ == 0) {
+#ifndef NDEBUG
+      in_dtor_ = true;
+#endif
+      delete static_cast<T*>(this);
+    }
+  }
+
+ private:
+  int ref_count_;
+#ifndef NDEBUG
+  bool in_dtor_;
+#endif
+
+  DISALLOW_EVIL_CONSTRUCTORS(RefCounted<T>);
+};
+
+//
+// A thread-safe variant of RefCounted<T>
+//
+//   class MyFoo : public base::RefCountedThreadSafe<MyFoo> {
+//    ...
+//   };
+//
+template <class T>
+class RefCountedThreadSafe {
+ public:
+  RefCountedThreadSafe() : ref_count_(0) {
+#ifndef NDEBUG
+    in_dtor_ = false;
+#endif
+  }
+
+  ~RefCountedThreadSafe() {
+#ifndef NDEBUG
+    DCHECK(in_dtor_) << "RefCountedThreadSafe object deleted without " <<
+                        "calling Release()";
+#endif
+  }
+
+  void AddRef() {
+#ifndef NDEBUG
+    DCHECK(!in_dtor_);
+#endif
+    AtomicIncrement(&ref_count_);
+  }
+
+  void Release() {
+#ifndef NDEBUG
+    DCHECK(!in_dtor_);
+#endif
+    // We need to insert memory barriers to ensure that state written before
+    // the reference count became 0 will be visible to a thread that has just
+    // made the count 0.
+    // TODO(wtc): Bug 1112286: use the barrier variant of AtomicDecrement.
+    if (AtomicDecrement(&ref_count_) == 0) {
+#ifndef NDEBUG
+      in_dtor_ = true;
+#endif
+      delete static_cast<T*>(this);
+    }
+  }
+
+ private:
+  int32 ref_count_;
+#ifndef NDEBUG
+  bool in_dtor_;
+#endif
+
+  DISALLOW_EVIL_CONSTRUCTORS(RefCountedThreadSafe<T>);
+};
+
+} // namespace base
+
+//
+// A smart pointer class for reference counted objects.  Use this class instead
+// of calling AddRef and Release manually on a reference counted object to
+// avoid common memory leaks caused by forgetting to Release an object
+// reference.  Sample usage:
+//
+//   class MyFoo : public RefCounted<MyFoo> {
+//    ...
+//   };
+//
+//   void some_function() {
+//     scoped_refptr<MyFoo> foo = new MyFoo();
+//     foo->Method(param);
+//     // |foo| is released when this function returns
+//   }
+//
+//   void some_other_function() {
+//     scoped_refptr<MyFoo> foo = new MyFoo();
+//     ...
+//     foo = NULL;  // explicitly releases |foo|
+//     ...
+//     if (foo)
+//       foo->Method(param);
+//   }
+//
+// The above examples show how scoped_refptr<T> acts like a pointer to T.
+// Given two scoped_refptr<T> classes, it is also possible to exchange
+// references between the two objects, like so:
+//
+//   {
+//     scoped_refptr<MyFoo> a = new MyFoo();
+//     scoped_refptr<MyFoo> b;
+//
+//     b.swap(a);
+//     // now, |b| references the MyFoo object, and |a| references NULL.
+//   }
+//
+// To make both |a| and |b| in the above example reference the same MyFoo
+// object, simply use the assignment operator:
+//
+//   {
+//     scoped_refptr<MyFoo> a = new MyFoo();
+//     scoped_refptr<MyFoo> b;
+//
+//     b = a;
+//     // now, |a| and |b| each own a reference to the same MyFoo object.
+//   }
+//
+template <class T>
+class scoped_refptr {
+ public:
+  scoped_refptr() : ptr_(NULL) {
+  }
+
+  scoped_refptr(T* p) : ptr_(p) {
+    if (ptr_)
+      ptr_->AddRef();
+  }
+
+  scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
+    if (ptr_)
+      ptr_->AddRef();
+  }
+
+  ~scoped_refptr() {
+    if (ptr_)
+      ptr_->Release();
+  }
+
+  T* get() const { return ptr_; }
+  operator T*() const { return ptr_; }
+  T* operator->() const { return ptr_; }
+
+  scoped_refptr<T>& operator=(T* p) {
+    // AddRef first so that self assignment should work
+    if (p)
+      p->AddRef();
+    if (ptr_ )
+      ptr_ ->Release();
+    ptr_ = p;
+    return *this;
+  }
+
+  scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
+    return *this = r.ptr_;
+  }
+
+  void swap(T** pp) {
+    T* p = ptr_;
+    ptr_ = *pp;
+    *pp = p;
+  }
+
+  void swap(scoped_refptr<T>& r) {
+    swap(&r.ptr_);
+  }
+
+ private:
+  T* ptr_;
+};
+
+#endif  // BASE_REF_COUNTED_H__