SkTScopedComPtr.h revision bd81a327b5728b51cac8642128bd2f165d078ef7 
1/*
2 * Copyright 2011 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkTScopedComPtr_DEFINED
9#define SkTScopedComPtr_DEFINED
10
11#include "SkLeanWindows.h"
12
13#ifdef SK_BUILD_FOR_WIN
14
15template<typename T>
16class SkBlockComRef : public T {
17private:
18    virtual ULONG STDMETHODCALLTYPE AddRef(void) = 0;
19    virtual ULONG STDMETHODCALLTYPE Release(void) = 0;
20};
21
22template<typename T> T* SkRefComPtr(T* ptr) {
23    ptr->AddRef();
24    return ptr;
25}
26
27template<typename T> T* SkSafeRefComPtr(T* ptr) {
28    if (ptr) {
29        ptr->AddRef();
30    }
31    return ptr;
32}
33
34template<typename T>
35class SkTScopedComPtr : SkNoncopyable {
36private:
37    T *fPtr;
38
39public:
40    explicit SkTScopedComPtr(T *ptr = nullptr) : fPtr(ptr) { }
41
42    ~SkTScopedComPtr() { this->reset();}
43
44    T &operator*() const { SkASSERT(fPtr != nullptr); return *fPtr; }
45
46    explicit operator bool() const { return fPtr != nullptr; }
47
48    SkBlockComRef<T> *operator->() const { return static_cast<SkBlockComRef<T>*>(fPtr); }
49
50    /**
51     * Returns the address of the underlying pointer.
52     * This is dangerous -- it breaks encapsulation and the reference escapes.
53     * Must only be used on instances currently pointing to NULL,
54     * and only to initialize the instance.
55     */
56    T **operator&() { SkASSERT(fPtr == nullptr); return &fPtr; }
57
58    T *get() const { return fPtr; }
59
60    void reset(T* ptr = nullptr) {
61        if (fPtr) {
62            fPtr->Release();
63        }
64        fPtr = ptr;
65    }
66
67    void swap(SkTScopedComPtr<T>& that) {
68        T* temp = this->fPtr;
69        this->fPtr = that.fPtr;
70        that.fPtr = temp;
71    }
72
73    T* release() {
74        T* temp = this->fPtr;
75        this->fPtr = nullptr;
76        return temp;
77    }
78};
79
80#endif  // SK_BUILD_FOR_WIN
81#endif  // SkTScopedComPtr_DEFINED
82