skia2/include/utils/win/SkTScopedComPtr.h

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkTScopedComPtr_DEFINED
#define SkTScopedComPtr_DEFINED

#include "SkTypes.h"
#include "SkTemplates.h"

template<typename T>
class SkBlockComRef : public T {
private:
    virtual ULONG STDMETHODCALLTYPE AddRef(void) = 0;
    virtual ULONG STDMETHODCALLTYPE Release(void) = 0;
};

template<typename T> T* SkRefComPtr(T* ptr) {
    ptr->AddRef();
    return ptr;
}

template<typename T> T* SkSafeRefComPtr(T* ptr) {
    if (ptr) {
        ptr->AddRef();
    }
    return ptr;
}

template<typename T>
class SkTScopedComPtr : SkNoncopyable {
private:
    T *fPtr;

public:
    explicit SkTScopedComPtr(T *ptr = NULL) : fPtr(ptr) { }
    ~SkTScopedComPtr() {
        this->reset();
    }
    T &operator*() const { SkASSERT(fPtr != NULL); return *fPtr; }
    SkBlockComRef<T> *operator->() const {
        return static_cast<SkBlockComRef<T>*>(fPtr);
    }
    /**
     * Returns the address of the underlying pointer.
     * This is dangerous -- it breaks encapsulation and the reference escapes.
     * Must only be used on instances currently pointing to NULL,
     * and only to initialize the instance.
     */
    T **operator&() { SkASSERT(fPtr == NULL); return &fPtr; }
    T *get() const { return fPtr; }
    void reset() {
        if (this->fPtr) {
            this->fPtr->Release();
            this->fPtr = NULL;
        }
    }

    void swap(SkTScopedComPtr<T>& that) {
        T* temp = this->fPtr;
        this->fPtr = that.fPtr;
        that.fPtr = temp;
    }

    T* release() {
        T* temp = this->fPtr;
        this->fPtr = NULL;
        return temp;
    }
};

#endif