pjs/xpcom/public/nsCOMPtr.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/*
* The contents of this file are subject to the Netscape Public License
* Version 1.0 (the "NPL"); you may not use this file except in
* compliance with the NPL. You may obtain a copy of the NPL at
* http://www.mozilla.org/NPL/
*
* Software distributed under the NPL is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
* for the specific language governing rights and limitations under the
* NPL.
*
* The Initial Developer of this code under the NPL is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All Rights
* Reserved.
*/
#ifndef nsCOMPtr_h___
#define nsCOMPtr_h___
// Wrapping includes can speed up compiles (see "Large Scale C++ Software Design")
#ifndef nsDebug_h___
#include "nsDebug.h"
// for |NS_PRECONDITION|
#endif
#ifndef nsISupports_h___
#include "nsISupports.h"
// for |nsresult|, |NS_ADDREF|, et al
#endif
/*
Public things defined in this file:
T* rawTptr;
class nsCOMPtr<T> nsCOMPtr<T> smartTptr;
null_nsCOMPtr() smartTptr = null_nsCOMPtr();
do_QueryInterface( nsISupports* ) smartTptr = do_QueryInterface(other_ptr);
do_QueryInterface( nsISupports*, nsresult* ) smartTptr = do_QueryInterface(other_ptr, &status);
dont_QueryInterface( T* ) smartTptr = dont_QueryInterface(rawTptr);
getter_AddRefs( nsCOMPtr<T>& )
getter_AddRefs( T* )
dont_AddRef( T* )
CallQueryInterface( nsISupports*, T** )
CallQueryInterface( nsISupports*, nsCOMPtr<T>* )
*/
/*
Having problems?
See the User Manual at:
<http://www.meer.net/ScottCollins/doc/nsCOMPtr.html>, or
<http://www.mozilla.org/projects/xpcom/nsCOMPtr.html>
*/
/*
TO DO...
+ Improve internal documentation
+ mention *&
+ alternatives for comparison
+ do_QueryInterface
*/
/*
WARNING:
This file defines several macros for internal use only. These macros begin with the
prefix |NSCAP_|. Do not use these macros in your own code. They are for internal use
only for cross-platform compatibility, and are subject to change without notice.
*/
/*
Set up some |#define|s to turn off a couple of troublesome C++ features.
Interestingly, none of the compilers barf on template stuff. These are set up automatically
by the autoconf system for all Unixes. (Temporarily, I hope) I have to define them
myself for Mac and Windows.
*/
// under Metrowerks (Mac), we don't have autoconf yet
#ifdef __MWERKS__
#define HAVE_CPP_USING
#define HAVE_CPP_EXPLICIT
#define HAVE_CPP_NEW_CASTS
#endif
// under VC++ (Windows), we don't have autoconf yet
#ifdef _MSC_VER
#define HAVE_CPP_EXPLICIT
#define HAVE_CPP_USING
#define HAVE_CPP_NEW_CASTS
#if (_MSC_VER<1100)
// before 5.0, VC++ couldn't handle explicit
#undef HAVE_CPP_EXPLICIT
#elif (_MSC_VER==1100)
// VC++5.0 has an internal compiler error (sometimes) without this
#undef HAVE_CPP_USING
#endif
#define NSCAP_FEATURE_INLINE_STARTASSIGNMENT
// under VC++, we win by inlining StartAssignment
#endif
/*
If the compiler doesn't support |explicit|, we'll just make it go away, trusting
that the builds under compilers that do have it will keep us on the straight and narrow.
*/
#ifndef HAVE_CPP_EXPLICIT
#define explicit
#endif
#ifdef HAVE_CPP_NEW_CASTS
#define NSCAP_REINTERPRET_CAST(T,x) reinterpret_cast<T>(x)
#else
#define NSCAP_REINTERPRET_CAST(T,x) ((T)(x))
#endif
#ifdef NSCAP_FEATURE_DEBUG_MACROS
#define NSCAP_ADDREF(ptr) NS_ADDREF(ptr)
#define NSCAP_RELEASE(ptr) NS_RELEASE(ptr)
#else
#define NSCAP_ADDREF(ptr) (ptr)->AddRef()
#define NSCAP_RELEASE(ptr) (ptr)->Release()
#endif
/*
WARNING:
VC++4.2 is very picky. To compile under VC++4.2, the classes must be defined
in an order that satisfies:
nsDerivedSafe < nsCOMPtr
nsDontAddRef < nsCOMPtr
nsCOMPtr < nsGetterAddRefs
The other compilers probably won't complain, so please don't reorder these
classes, on pain of breaking 4.2 compatibility.
*/
template <class T>
class nsDerivedSafe : public T
/*
No client should ever see or have to type the name of this class. It is the
artifact that makes it a compile-time error to call |AddRef| and |Release|
on a |nsCOMPtr|. DO NOT USE THIS TYPE DIRECTLY IN YOUR CODE.
See |nsCOMPtr::operator->|, |nsCOMPtr::operator*|, et al.
*/
{
private:
#ifdef HAVE_CPP_USING
using T::AddRef;
using T::Release;
#else
NS_IMETHOD_(nsrefcnt) AddRef(void);
NS_IMETHOD_(nsrefcnt) Release(void);
#endif
void operator delete( void*, size_t ); // NOT TO BE IMPLEMENTED
// declaring |operator delete| private makes calling delete on an interface pointer a compile error
nsDerivedSafe<T>& operator=( const nsDerivedSafe<T>& ); // NOT TO BE IMPLEMENTED
// you may not call |operator=()| through a dereferenced |nsCOMPtr|, because you'd get the wrong one
};
#if !defined(HAVE_CPP_USING) && defined(NEED_CPP_UNUSED_IMPLEMENTATIONS)
template <class T>
nsrefcnt
nsDerivedSafe<T>::AddRef()
{
return 0;
}
template <class T>
nsrefcnt
nsDerivedSafe<T>::Release()
{
return 0;
}
#endif
template <class T>
struct nsDontQueryInterface
/*
...
DO NOT USE THIS TYPE DIRECTLY IN YOUR CODE. Use |dont_QueryInterface()| instead.
*/
{
explicit
nsDontQueryInterface( T* aRawPtr )
: mRawPtr(aRawPtr)
{
// nothing else to do here
}
T* mRawPtr;
};
template <class T>
inline
const nsDontQueryInterface<T>
dont_QueryInterface( T* aRawPtr )
{
return nsDontQueryInterface<T>(aRawPtr);
}
struct nsQueryInterface
/*
...
DO NOT USE THIS TYPE DIRECTLY IN YOUR CODE. Use |do_QueryInterface()| instead.
*/
{
explicit
nsQueryInterface( nsISupports* aRawPtr, nsresult* error = 0 )
: mRawPtr(aRawPtr),
mErrorPtr(error)
{
// nothing else to do here
}
nsISupports* mRawPtr;
nsresult* mErrorPtr;
};
inline
const nsQueryInterface
do_QueryInterface( nsISupports* aRawPtr, nsresult* error = 0 )
{
return nsQueryInterface(aRawPtr, error);
}
inline
const nsQueryInterface
null_nsCOMPtr()
/*
You can use this to assign |NULL| into an |nsCOMPtr|, e.g.,
myPtr = null_nsCOMPtr();
*/
{
typedef nsISupports* nsISupports_Ptr;
return nsQueryInterface(nsISupports_Ptr(0));
}
template <class T>
struct nsDontAddRef
/*
...cooperates with |nsCOMPtr| to allow you to assign in a pointer _without_
|AddRef|ing it. You would rarely use this directly, but rather through the
machinery of |getter_AddRefs| in the argument list to functions that |AddRef|
their results before returning them to the caller.
DO NOT USE THIS TYPE DIRECTLY IN YOUR CODE. Use |getter_AddRefs()| instead.
See also |getter_AddRefs()| and |class nsGetterAddRefs|.
*/
{
explicit
nsDontAddRef( T* aRawPtr )
: mRawPtr(aRawPtr)
{
// nothing else to do here
}
T* mRawPtr;
};
template <class T>
inline
const nsDontAddRef<T>
getter_AddRefs( T* aRawPtr )
/*
...makes typing easier, because it deduces the template type, e.g.,
you write |dont_AddRef(fooP)| instead of |nsDontAddRef<IFoo>(fooP)|.
*/
{
return nsDontAddRef<T>(aRawPtr);
}
// This call is now deprecated. Use |getter_AddRefs()| instead.
template <class T>
inline
const nsDontAddRef<T>
dont_AddRef( T* aRawPtr )
{
return nsDontAddRef<T>(aRawPtr);
}
class nsCOMPtr_base
/*
...factors implementation for all template versions of |nsCOMPtr|.
*/
{
public:
nsCOMPtr_base( nsISupports* rawPtr = 0 )
: mRawPtr(rawPtr)
{
// nothing else to do here
}
~nsCOMPtr_base()
{
if ( mRawPtr )
NSCAP_RELEASE(mRawPtr);
}
NS_EXPORT void assign_with_AddRef( nsISupports* );
NS_EXPORT void assign_with_QueryInterface( nsISupports*, const nsIID&, nsresult* );
NS_EXPORT void** begin_assignment();
protected:
nsISupports* mRawPtr;
};
template <class T>
class nsCOMPtr : private nsCOMPtr_base
/*
...
*/
{
public:
typedef T element_type;
nsCOMPtr()
// : nsCOMPtr_base(0)
{
// nothing else to do here
}
nsCOMPtr( const nsQueryInterface& aSmartPtr )
// : nsCOMPtr_base(0)
{
assign_with_QueryInterface(aSmartPtr.mRawPtr, T::GetIID(), aSmartPtr.mErrorPtr);
}
nsCOMPtr( const nsDontAddRef<T>& aSmartPtr )
: nsCOMPtr_base(aSmartPtr.mRawPtr)
{
// nothing else to do here
}
nsCOMPtr( const nsDontQueryInterface<T>& aSmartPtr )
: nsCOMPtr_base(aSmartPtr.mRawPtr)
{
if ( mRawPtr )
NSCAP_ADDREF(mRawPtr);
}
nsCOMPtr( const nsCOMPtr<T>& aSmartPtr )
: nsCOMPtr_base(aSmartPtr.mRawPtr)
{
if ( mRawPtr )
NSCAP_ADDREF(mRawPtr);
}
nsCOMPtr<T>&
operator=( const nsQueryInterface& rhs )
{
assign_with_QueryInterface(rhs.mRawPtr, T::GetIID(), rhs.mErrorPtr);
return *this;
}
nsCOMPtr<T>&
operator=( const nsDontAddRef<T>& rhs )
{
if ( mRawPtr )
NSCAP_RELEASE(mRawPtr);
mRawPtr = rhs.mRawPtr;
return *this;
}
nsCOMPtr<T>&
operator=( const nsDontQueryInterface<T>& rhs )
{
assign_with_AddRef(rhs.mRawPtr);
return *this;
}
nsCOMPtr<T>&
operator=( const nsCOMPtr<T>& rhs )
{
assign_with_AddRef(rhs.mRawPtr);
return *this;
}
nsDerivedSafe<T>*
get() const
// returns a |nsDerivedSafe<T>*| to deny clients the use of |AddRef| and |Release|
{
return NSCAP_REINTERPRET_CAST(nsDerivedSafe<T>*, mRawPtr);
}
nsDerivedSafe<T>*
operator->() const
// returns a |nsDerivedSafe<T>*| to deny clients the use of |AddRef| and |Release|
{
NS_PRECONDITION(mRawPtr != 0, "You can't dereference a NULL nsCOMPtr with operator->().");
return get();
}
nsDerivedSafe<T>&
operator*() const
// returns a |nsDerivedSafe<T>*| to deny clients the use of |AddRef| and |Release|
{
NS_PRECONDITION(mRawPtr != 0, "You can't dereference a NULL nsCOMPtr with operator*().");
return *get();
}
operator nsDerivedSafe<T>*() const
{
return get();
}
#if 0
private:
friend class nsGetterAddRefs<T>;
/*
In a perfect world, the following member function, |StartAssignment|, would be private.
It is and should be only accessed by the closely related class |nsGetterAddRefs<T>|.
Unfortunately, some compilers---most notably VC++5.0---fail to grok the
friend declaration above or in any alternate acceptable form. So, physically
it will be public (until our compilers get smarter); but it is not to be
considered part of the logical public interface.
*/
#endif
T**
StartAssignment()
{
#ifndef NSCAP_FEATURE_INLINE_STARTASSIGNMENT
return NSCAP_REINTERPRET_CAST(T**, begin_assignment());
#else
if ( mRawPtr )
NSCAP_RELEASE(mRawPtr);
mRawPtr = 0;
return NSCAP_REINTERPRET_CAST(T**, &mRawPtr);
#endif
}
};
template <class T>
class nsGetterAddRefs
/*
...
This class is designed to be used for anonymous temporary objects in the
argument list of calls that return COM interface pointers, e.g.,
nsCOMPtr<IFoo> fooP;
...->QueryInterface(iid, getter_AddRefs(fooP))
DO NOT USE THIS TYPE DIRECTLY IN YOUR CODE. Use |getter_AddRefs()| instead.
When initialized with a |nsCOMPtr|, as in the example above, it returns
a |void**| (or |T**| if needed) that the outer call (|QueryInterface| in this
case) can fill in.
*/
{
public:
explicit
nsGetterAddRefs( nsCOMPtr<T>& aSmartPtr )
: mTargetSmartPtr(aSmartPtr)
{
// nothing else to do
}
operator void**()
{
return NSCAP_REINTERPRET_CAST(void**, mTargetSmartPtr.StartAssignment());
}
T*&
operator*()
{
return *(mTargetSmartPtr.StartAssignment());
}
operator T**()
{
return mTargetSmartPtr.StartAssignment();
}
private:
nsCOMPtr<T>& mTargetSmartPtr;
};
template <class T>
inline
nsGetterAddRefs<T>
getter_AddRefs( nsCOMPtr<T>& aSmartPtr )
/*
Used around a |nsCOMPtr| when
...makes the class |nsGetterAddRefs<T>| invisible.
*/
{
return nsGetterAddRefs<T>(aSmartPtr);
}
template <class SourceType, class DestinationType>
inline
nsresult
CallQueryInterface( SourceType* aSource, nsCOMPtr<DestinationType>* aDestination )
// a type-safe shortcut for calling the |QueryInterface()| member function
{
NS_PRECONDITION(aSource, "null parameter");
NS_PRECONDITION(aDestination, "null parameter");
return aSource->QueryInterface(DestinationType::GetIID(), getter_AddRefs(*aDestination));
}
#endif // !defined(nsCOMPtr_h___)