1
2/*
3 * Copyright 2011 Google Inc.
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#ifndef SkTScopedPtr_DEFINED
11#define SkTScopedPtr_DEFINED
12
13#include "SkTypes.h"
14
15/** \class SkTScopedPtr
16  A SkTScopedPtr<T> is like a T*, except that the destructor of SkTScopedPtr<T>
17  automatically deletes the pointer it holds (if any).  That is, SkTScopedPtr<T>
18  owns the T object that it points to.  Like a T*, a SkTScopedPtr<T> may hold
19  either NULL or a pointer to a T object.  Also like T*, SkTScopedPtr<T> is
20  thread-compatible, and once you dereference it, you get the threadsafety
21  guarantees of T.
22
23  The size of a SkTScopedPtr is small: sizeof(SkTScopedPtr<T>) == sizeof(T*)
24*/
25template <typename T> class SkTScopedPtr : SkNoncopyable {
26public:
27    explicit SkTScopedPtr(T* o = NULL) : fObj(o) {}
28    ~SkTScopedPtr() {
29        enum { kTypeMustBeComplete = sizeof(T) };
30        delete fObj;
31    }
32
33    /** Delete the current object, if any.  Then take ownership of the
34        passed object.
35     */
36    void reset(T* o = NULL) {
37        if (o != fObj) {
38            enum { kTypeMustBeComplete = sizeof(T) };
39            delete fObj;
40            fObj = o;
41        }
42    }
43
44    /** Without deleting the current object, return it and forget about it.
45        Similar to calling get() and reset(), but the object is not deleted.
46     */
47    T* release() {
48        T* retVal = fObj;
49        fObj = NULL;
50        return retVal;
51    }
52
53    T& operator*() const {
54        SkASSERT(fObj != NULL);
55        return *fObj;
56    }
57    T* operator->() const  {
58        SkASSERT(fObj != NULL);
59        return fObj;
60    }
61    T* get() const { return fObj; }
62
63    bool operator==(T* o) const { return fObj == o; }
64    bool operator!=(T* o) const { return fObj != o; }
65
66private:
67    T* fObj;
68
69    // Forbid comparison of SkTScopedPtr types.  If T2 != T, it doesn't make
70    // sense, and if T2 == T, it still doesn't make sense because the same
71    // object can't be owned by two different scoped_ptrs.
72    template <class T2> bool operator==(SkTScopedPtr<T2> const& o2) const;
73    template <class T2> bool operator!=(SkTScopedPtr<T2> const& o2) const;
74};
75
76#endif
77