base/scoped_cftyperef.h

// Copyright (c) 2006-2008 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.

#ifndef BASE_SCOPED_CFTYPEREF_H_
#define BASE_SCOPED_CFTYPEREF_H_

#include <CoreFoundation/CoreFoundation.h>
#include "base/basictypes.h"

// scoped_cftyperef<> is patterned after scoped_ptr<>, but maintains ownership
// of a CoreFoundation object: any object that can be represented as a
// CFTypeRef.  Style deviations here are solely for compatibility with
// scoped_ptr<>'s interface, with which everyone is already familiar.
//
// When scoped_cftyperef<> takes ownership of an object (in the constructor or
// in reset()), it takes over the caller's existing ownership claim.  The 
// caller must own the object it gives to scoped_cftyperef<>, and relinquishes
// an ownership claim to that object.  scoped_cftyperef<> does not call
// CFRetain().
template<typename CFT>
class scoped_cftyperef {
 public:
  typedef CFT element_type;

  explicit scoped_cftyperef(CFT object = NULL)
      : object_(object) {
  }

  ~scoped_cftyperef() {
    if (object_)
      CFRelease(object_);
  }

  void reset(CFT object = NULL) {
    if (object_)
      CFRelease(object_);
    object_ = object;
  }

  bool operator==(CFT that) const {
    return object_ == that;
  }

  bool operator!=(CFT that) const {
    return object_ != that;
  }

  operator CFT() const {
    return object_;
  }

  CFT get() const {
    return object_;
  }

  void swap(scoped_cftyperef& that) {
    CFT temp = that.object_;
    that.object_ = object_;
    object_ = temp;
  }

  // scoped_cftyperef<>::release() is like scoped_ptr<>::release.  It is NOT
  // a wrapper for CFRelease().  To force a scoped_cftyperef<> object to call
  // CFRelease(), use scoped_cftyperef<>::reset().
  CFT release() {
    CFT temp = object_;
    object_ = NULL;
    return temp;
  }

 private:
  CFT object_;

  DISALLOW_COPY_AND_ASSIGN(scoped_cftyperef);
};

#endif  // BASE_SCOPED_CFTYPEREF_H_