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/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
/* Cairo - a vector graphics library with display and print output
*
* Copyright <A9> 2010 Mozilla Foundation
*
* This library is free software; you can redistribute it and/or
* modify it either under the terms of the GNU Lesser General Public
* License version 2.1 as published by the Free Software Foundation
* (the "LGPL") or, at your option, under the terms of the Mozilla
* Public License Version 1.1 (the "MPL"). If you do not alter this
* notice, a recipient may use your version of this file under either
* the MPL or the LGPL.
*
* You should have received a copy of the LGPL along with this library
* in the file COPYING-LGPL-2.1; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
* You should have received a copy of the MPL along with this library
* in the file COPYING-MPL-1.1
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
* OF ANY KIND, either express or implied. See the LGPL or the MPL for
* the specific language governing rights and limitations.
*
* The Original Code is the cairo graphics library.
*
* The Initial Developer of the Original Code is the Mozilla Foundation
*
* Contributor(s):
* Bas Schouten <bschouten@mozilla.com>
*/
#ifndef CAIRO_WIN32_REFPTR_H
#define CAIRO_WIN32_REFPTR_H
template<typename T> class TemporaryRef;
/*
* RefPtr points to a refcounted thing that has AddRef and Release
* methods to increase/decrease the refcount, respectively. After a
* RefPtr<T> is assigned a T*, the T* can be used through the RefPtr
* as if it were a T*.
*
* A RefPtr can forget its underlying T*, which results in the T*
* being wrapped in a temporary object until the T* is either
* re-adopted from or released by the temporary.
*/
template<typename T>
class RefPtr
{
// To allow them to use unref()
friend class TemporaryRef<T>;
struct dontRef {};
public:
RefPtr() : ptr(0) { }
RefPtr(const RefPtr& o) : ptr(ref(o.ptr)) {}
RefPtr(const TemporaryRef<T>& o) : ptr(o.drop()) {}
RefPtr(T* t) : ptr(ref(t)) {}
template<typename U>
RefPtr(const RefPtr<U>& o) : ptr(ref(o.get())) {}
~RefPtr() { unref(ptr); }
RefPtr& operator=(const RefPtr& o) {
assign(ref(o.ptr));
return *this;
}
RefPtr& operator=(const TemporaryRef<T>& o) {
assign(o.drop());
return *this;
}
RefPtr& operator=(T* t) {
assign(ref(t));
return *this;
}
template<typename U>
RefPtr& operator=(const RefPtr<U>& o) {
assign(ref(o.get()));
return *this;
}
TemporaryRef<T> forget() {
T* tmp = ptr;
ptr = 0;
return TemporaryRef<T>(tmp, dontRef());
}
T* get() const { return ptr; }
operator T*() const { return ptr; }
T* operator->() const { return ptr; }
T& operator*() const { return *ptr; }
template<typename U>
operator TemporaryRef<U>() { return TemporaryRef<U>(ptr); }
/**
* WARNING for ease of use, passing a reference will release/clear out ptr!
* We null out the ptr before returning its address so people passing byref
* as input will most likely get functions returning errors rather than accessing
* freed memory. Further more accessing it after this point if it hasn't
* been set will produce a null pointer dereference.
*/
T** operator&()
{
if (ptr) {
ptr->Release();
ptr = NULL;
}
return &ptr;
}
private:
void assign(T* t) {
unref(ptr);
ptr = t;
}
T* ptr;
static inline T* ref(T* t) {
if (t) {
t->AddRef();
}
return t;
}
static inline void unref(T* t) {
if (t) {
t->Release();
}
}
};
/*
* TemporaryRef<T> represents an object that holds a temporary
* reference to a T. TemporaryRef objects can't be manually ref'd or
* unref'd (being temporaries, not lvalues), so can only relinquish
* references to other objects, or unref on destruction.
*/
template<typename T>
class TemporaryRef
{
// To allow it to construct TemporaryRef from a bare T*
friend class RefPtr<T>;
typedef typename RefPtr<T>::dontRef dontRef;
public:
TemporaryRef(T* t) : ptr(RefPtr<T>::ref(t)) {}
TemporaryRef(const TemporaryRef& o) : ptr(o.drop()) {}
template<typename U>
TemporaryRef(const TemporaryRef<U>& o) : ptr(o.drop()) {}
~TemporaryRef() { RefPtr<T>::unref(ptr); }
T* drop() const {
T* tmp = ptr;
ptr = 0;
return tmp;
}
private:
TemporaryRef(T* t, const dontRef&) : ptr(t) {}
mutable T* ptr;
TemporaryRef();
TemporaryRef& operator=(const TemporaryRef&);
};
#endif
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