pjs/xpcom/base/nsISupportsUtils.h

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* 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 __nsISupportsUtils_h
#define __nsISupportsUtils_h
/***************************************************************************/
/* this section copied from the hand written nsISupports.h */
#include "nsDebug.h"
#include "nsID.h"
#include "nsIID.h"
#include "nsError.h"
#include "pratom.h" /* needed for PR_AtomicIncrement and PR_AtomicDecrement */
#if defined(NS_MT_SUPPORTED)
#include "prcmon.h"
#endif /* NS_MT_SUPPORTED */
// under Metrowerks (Mac), we don't have autoconf yet
#ifdef __MWERKS__
#define HAVE_CPP_SPECIALIZATION
#endif
// under VC++ (Windows), we don't have autoconf yet
#if defined(_MSC_VER) && (_MSC_VER>=1100)
// VC++ 5.0 and greater implement template specialization, 4.2 is unknown
#define HAVE_CPP_SPECIALIZATION
#endif
#ifdef HAVE_CPP_SPECIALIZATION
#define NSCAP_FEATURE_HIDE_NSISUPPORTS_GETIID
#endif
/*@{*/
////////////////////////////////////////////////////////////////////////////////
/**
* IID for the nsISupports interface
* {00000000-0000-0000-c000-000000000046}
*
* To maintain binary compatibility with COM's nsIUnknown, we define the IID
* of nsISupports to be the same as that of COM's nsIUnknown.
*/
#define NS_ISUPPORTS_IID \
{ 0x00000000, 0x0000, 0x0000, \
{0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46} }
/**
* Reference count values
*
* This is type of return value from Addref() and Release() in nsISupports.
* nsIUnknown of COM returns a unsigned long from equivalent functions.
* To maintain binary compatibility of nsISupports with nsIUnknown, we are
* doing this ifdeffing.
*/
#if defined(XP_PC) && PR_BYTES_PER_LONG == 4
typedef unsigned long nsrefcnt;
#else
typedef PRUint32 nsrefcnt;
#endif
#include "nsTraceRefcnt.h"
/**
* Basic component object model interface. Objects which implement
* this interface support runtime interface discovery (QueryInterface)
* and a reference counted memory model (AddRef/Release). This is
* modelled after the win32 IUnknown API.
*/
class nsISupports {
public:
#ifndef NSCAP_FEATURE_HIDE_NSISUPPORTS_GETIID
static const nsIID& GetIID() { static nsIID iid = NS_ISUPPORTS_IID; return iid; }
#endif
/**
* @name Methods
*/
//@{
/**
* A run time mechanism for interface discovery.
* @param aIID [in] A requested interface IID
* @param aInstancePtr [out] A pointer to an interface pointer to
* receive the result.
* @return <b>NS_OK</b> if the interface is supported by the associated
* instance, <b>NS_NOINTERFACE</b> if it is not.
* <b>NS_ERROR_INVALID_POINTER</b> if <i>aInstancePtr</i> is <b>NULL</b>.
*/
NS_IMETHOD QueryInterface(REFNSIID aIID,
void** aInstancePtr) = 0;
/**
* Increases the reference count for this interface.
* The associated instance will not be deleted unless
* the reference count is returned to zero.
*
* @return The resulting reference count.
*/
NS_IMETHOD_(nsrefcnt) AddRef(void) = 0;
/**
* Decreases the reference count for this interface.
* Generally, if the reference count returns to zero,
* the associated instance is deleted.
*
* @return The resulting reference count.
*/
NS_IMETHOD_(nsrefcnt) Release(void) = 0;
//@}
};
/*@}*/
/***************************************************************************/
/**
* A macro to build the static const IID accessor method
*/
#define NS_DEFINE_STATIC_IID_ACCESSOR(the_iid) \
static const nsIID& GetIID() {static nsIID iid = the_iid; return iid;}
/**
* A macro to build the static const CID accessor method
*/
#define NS_DEFINE_STATIC_CID_ACCESSOR(the_cid) \
static const nsID& GetCID() {static nsID cid = the_cid; return cid;}
/**
* Some convenience macros for implementing AddRef and Release
*/
/**
* Declare the reference count variable and the implementations of the
* AddRef and QueryInterface methods.
*/
#define NS_DECL_ISUPPORTS \
public: \
NS_IMETHOD QueryInterface(REFNSIID aIID, \
void** aInstancePtr); \
NS_IMETHOD_(nsrefcnt) AddRef(void); \
NS_IMETHOD_(nsrefcnt) Release(void); \
protected: \
nsrefcnt mRefCnt; \
public:
#define NS_DECL_ISUPPORTS_EXPORTED \
public: \
NS_EXPORT NS_IMETHOD QueryInterface(REFNSIID aIID, \
void** aInstancePtr); \
NS_EXPORT NS_IMETHOD_(nsrefcnt) AddRef(void); \
NS_EXPORT NS_IMETHOD_(nsrefcnt) Release(void); \
protected: \
nsrefcnt mRefCnt; \
public:
////////////////////////////////////////////////////////////////////////////////
/**
* Initialize the reference count variable. Add this to each and every
* constructor you implement.
*/
#define NS_INIT_REFCNT() mRefCnt = 0
#define NS_INIT_ISUPPORTS() NS_INIT_REFCNT() // what it should have been called in the first place
/**
* Use this macro to implement the AddRef method for a given <i>_class</i>
* @param _class The name of the class implementing the method
*/
#define NS_IMPL_ADDREF(_class) \
NS_IMETHODIMP_(nsrefcnt) _class::AddRef(void) \
{ \
NS_PRECONDITION(PRInt32(mRefCnt) >= 0, "illegal refcnt"); \
++mRefCnt; \
NS_LOG_ADDREF(this, mRefCnt, __FILE__, __LINE__); \
return mRefCnt; \
}
/**
* Use this macro to implement the Release method for a given <i>_class</i>
* @param _class The name of the class implementing the method
*/
#define NS_IMPL_RELEASE(_class) \
NS_IMETHODIMP_(nsrefcnt) _class::Release(void) \
{ \
NS_PRECONDITION(0 != mRefCnt, "dup release"); \
--mRefCnt; \
NS_LOG_RELEASE(this, mRefCnt, __FILE__, __LINE__); \
if (mRefCnt == 0) { \
NS_DELETEXPCOM(this); \
return 0; \
} \
return mRefCnt; \
}
////////////////////////////////////////////////////////////////////////////////
/*
* Some convenience macros for implementing QueryInterface
*/
/**
* This implements query interface with two assumptions: First, the
* class in question implements nsISupports and its own interface and
* nothing else. Second, the implementation of the class's primary
* inheritance chain leads to its own interface.
*
* @param _class The name of the class implementing the method
* @param _classiiddef The name of the #define symbol that defines the IID
* for the class (e.g. NS_ISUPPORTS_IID)
*/
#define NS_IMPL_QUERY_INTERFACE(_class,_classiiddef) \
NS_IMETHODIMP _class::QueryInterface(REFNSIID aIID, void** aInstancePtr) \
{ \
if (NULL == aInstancePtr) { \
return NS_ERROR_NULL_POINTER; \
} \
\
*aInstancePtr = NULL; \
\
static NS_DEFINE_IID(kClassIID, _classiiddef); \
if (aIID.Equals(kClassIID)) { \
*aInstancePtr = (void*) this; \
NS_ADDREF_THIS(); \
return NS_OK; \
} \
if (aIID.Equals(nsCOMTypeInfo<nsISupports>::GetIID())) { \
*aInstancePtr = (void*) ((nsISupports*)this); \
NS_ADDREF_THIS(); \
return NS_OK; \
} \
return NS_NOINTERFACE; \
}
#define NS_IMPL_QUERY_INTERFACE2(_class, _c1, _c2) \
NS_IMETHODIMP _class::QueryInterface(REFNSIID aIID, void** aInstancePtr) \
{ \
if (NULL == aInstancePtr) { \
return NS_ERROR_NULL_POINTER; \
} \
\
*aInstancePtr = NULL; \
\
if (aIID.Equals(nsCOMTypeInfo<_c1>::GetIID())) { \
*aInstancePtr = (void*) ((_c1*)this); \
NS_ADDREF_THIS(); \
return NS_OK; \
} \
if (aIID.Equals(nsCOMTypeInfo<_c2>::GetIID())) { \
*aInstancePtr = (void*) ((_c2*)this); \
NS_ADDREF_THIS(); \
return NS_OK; \
} \
if (aIID.Equals(nsCOMTypeInfo<nsISupports>::GetIID())) { \
*aInstancePtr = (void*) ((_c1*)this); \
NS_ADDREF_THIS(); \
return NS_OK; \
} \
return NS_NOINTERFACE; \
}
/**
* Convenience macro for implementing all nsISupports methods for
* a simple class.
* @param _class The name of the class implementing the method
* @param _classiiddef The name of the #define symbol that defines the IID
* for the class (e.g. NS_ISUPPORTS_IID)
*/
#define NS_IMPL_ISUPPORTS(_class,_classiiddef) \
NS_IMPL_ADDREF(_class) \
NS_IMPL_RELEASE(_class) \
NS_IMPL_QUERY_INTERFACE(_class,_classiiddef)
#define NS_IMPL_ISUPPORTS2(_class, _c1, _c2) \
NS_IMPL_ADDREF(_class) \
NS_IMPL_RELEASE(_class) \
NS_IMPL_QUERY_INTERFACE2(_class, _c1, _c2)
////////////////////////////////////////////////////////////////////////////////
/**
* Declare that you're going to inherit from something that already
* implements nsISupports, but also implements an additional interface, thus
* causing an ambiguity. In this case you don't need another mRefCnt, you
* just need to forward the definitions to the appropriate superclass. E.g.
*
* class Bar : public Foo, public nsIBar { // both provide nsISupports
* public:
* NS_DECL_ISUPPORTS_INHERITED
* ...other nsIBar and Bar methods...
* };
*/
#define NS_DECL_ISUPPORTS_INHERITED \
public: \
NS_IMETHOD QueryInterface(REFNSIID aIID, \
void** aInstancePtr); \
NS_IMETHOD_(nsrefcnt) AddRef(void); \
NS_IMETHOD_(nsrefcnt) Release(void); \
/**
* These macros can be used in conjunction with NS_DECL_ISUPPORTS_INHERITED
* to implement the nsISupports methods, forwarding the invocations to a
* superclass that already implements nsISupports.
*
* Note that I didn't make these inlined because they're virtual methods.
*/
#define NS_IMPL_ADDREF_INHERITED(Class, Super) \
NS_IMETHODIMP_(nsrefcnt) Class::AddRef(void) \
{ \
return Super::AddRef(); \
} \
#define NS_IMPL_RELEASE_INHERITED(Class, Super) \
NS_IMETHODIMP_(nsrefcnt) Class::Release(void) \
{ \
return Super::Release(); \
} \
#define NS_IMPL_QUERY_INTERFACE_INHERITED(Class, Super, AdditionalInterface) \
NS_IMETHODIMP Class::QueryInterface(REFNSIID aIID, void** aInstancePtr) \
{ \
if (!aInstancePtr) return NS_ERROR_NULL_POINTER; \
if (aIID.Equals(AdditionalInterface::GetIID())) { \
*aInstancePtr = NS_STATIC_CAST(AdditionalInterface*, this); \
NS_ADDREF_THIS(); \
return NS_OK; \
} \
return Super::QueryInterface(aIID, aInstancePtr); \
} \
#define NS_IMPL_ISUPPORTS_INHERITED(Class, Super, AdditionalInterface) \
NS_IMPL_QUERY_INTERFACE_INHERITED(Class, Super, AdditionalInterface) \
NS_IMPL_ADDREF_INHERITED(Class, Super) \
NS_IMPL_RELEASE_INHERITED(Class, Super) \
////////////////////////////////////////////////////////////////////////////////
/**
*
* Threadsafe implementations of the ISupports convenience macros
*
*/
/**
* IID for the nsIsThreadsafe interface
* {88210890-47a6-11d2-bec3-00805f8a66dc}
*
* This interface is *only* used for debugging purposes to determine if
* a given component is threadsafe.
*/
#define NS_ISTHREADSAFE_IID \
{ 0x88210890, 0x47a6, 0x11d2, \
{0xbe, 0xc3, 0x00, 0x80, 0x5f, 0x8a, 0x66, 0xdc} }
#if defined(NS_MT_SUPPORTED)
#define NS_LOCK_INSTANCE() \
PR_CEnterMonitor((void*)this)
#define NS_UNLOCK_INSTANCE() \
PR_CExitMonitor((void*)this)
/**
* Use this macro to implement the AddRef method for a given <i>_class</i>
* @param _class The name of the class implementing the method
*/
#define NS_IMPL_THREADSAFE_ADDREF(_class) \
NS_IMETHODIMP_(nsrefcnt) _class::AddRef(void) \
{ \
NS_PRECONDITION(PRInt32(mRefCnt) >= 0, "illegal refcnt"); \
return PR_AtomicIncrement((PRInt32*)&mRefCnt); \
}
/**
* Use this macro to implement the Release method for a given <i>_class</i>
* @param _class The name of the class implementing the method
*/
#define NS_IMPL_THREADSAFE_RELEASE(_class) \
nsrefcnt _class::Release(void) \
{ \
nsrefcnt count; \
NS_PRECONDITION(0 != mRefCnt, "dup release"); \
count = PR_AtomicDecrement((PRInt32 *)&mRefCnt); \
if (0 == count) { \
NS_DELETEXPCOM(this); \
return 0; \
} \
return count; \
}
////////////////////////////////////////////////////////////////////////////////
/*
* Some convenience macros for implementing QueryInterface
*/
/**
* This implements query interface with two assumptions: First, the
* class in question implements nsISupports and its own interface and
* nothing else. Second, the implementation of the class's primary
* inheritance chain leads to its own interface.
*
* @param _class The name of the class implementing the method
* @param _classiiddef The name of the #define symbol that defines the IID
* for the class (e.g. NS_ISUPPORTS_IID)
*/
#if defined(NS_DEBUG)
#define NS_VERIFY_THREADSAFE_INTERFACE(_iface) \
if (NULL != (_iface)) { \
nsISupports* tmp; \
static NS_DEFINE_IID(kIsThreadsafeIID, NS_ISTHREADSAFE_IID); \
NS_PRECONDITION((NS_OK == _iface->QueryInterface(kIsThreadsafeIID, \
(void**)&tmp)), \
"Interface is not threadsafe"); \
}
#define NS_IMPL_THREADSAFE_QUERY_INTERFACE(_class,_classiiddef) \
NS_IMETHODIMP _class::QueryInterface(REFNSIID aIID, void** aInstancePtr) \
{ \
if (NULL == aInstancePtr) { \
return NS_ERROR_NULL_POINTER; \
} \
\
*aInstancePtr = NULL; \
\
static NS_DEFINE_IID(kISupportsIID, NS_ISUPPORTS_IID); \
static NS_DEFINE_IID(kIsThreadsafeIID, NS_ISTHREADSAFE_IID); \
static NS_DEFINE_IID(kClassIID, _classiiddef); \
if (aIID.Equals(kClassIID)) { \
*aInstancePtr = (void*) this; \
NS_ADDREF_THIS(); \
return NS_OK; \
} \
if (aIID.Equals(kISupportsIID)) { \
*aInstancePtr = (void*) ((nsISupports*)this); \
NS_ADDREF_THIS(); \
return NS_OK; \
} \
if (aIID.Equals(kIsThreadsafeIID)) { \
return NS_OK; \
} \
return NS_NOINTERFACE; \
}
#else /* !NS_DEBUG */
#define NS_VERIFY_THREADSAFE_INTERFACE(_iface)
#define NS_IMPL_THREADSAFE_QUERY_INTERFACE(_class,_classiiddef) \
NS_IMPL_QUERY_INTERFACE(_class, _classiiddef)
#endif /* !NS_DEBUG */
/**
* Convenience macro for implementing all nsISupports methods for
* a simple class.
* @param _class The name of the class implementing the method
* @param _classiiddef The name of the #define symbol that defines the IID
* for the class (e.g. NS_ISUPPORTS_IID)
*/
#define NS_IMPL_THREADSAFE_ISUPPORTS(_class,_classiiddef) \
NS_IMPL_THREADSAFE_ADDREF(_class) \
NS_IMPL_THREADSAFE_RELEASE(_class) \
NS_IMPL_THREADSAFE_QUERY_INTERFACE(_class,_classiiddef)
#else /* !NS_MT_SUPPORTED */
#define NS_LOCK_INSTANCE()
#define NS_UNLOCK_INSTANCE()
#define NS_IMPL_THREADSAFE_ADDREF(_class) NS_IMPL_ADDREF(_class)
#define NS_IMPL_THREADSAFE_RELEASE(_class) NS_IMPL_RELEASE(_class)
#define NS_VERIFY_THREADSAFE_INTERFACE(_iface)
#define NS_IMPL_THREADSAFE_QUERY_INTERFACE(_class,_classiiddef) \
NS_IMPL_QUERY_INTERFACE(_class, _classiiddef)
#define NS_IMPL_THREADSAFE_ISUPPORTS(_class,_classiiddef) \
NS_IMPL_ADDREF(_class) \
NS_IMPL_RELEASE(_class) \
NS_IMPL_QUERY_INTERFACE(_class,_classiiddef)
#endif /* !NS_MT_SUPPORTED */
////////////////////////////////////////////////////////////////////////////////
// Debugging Macros
////////////////////////////////////////////////////////////////////////////////
/**
* Macro for instantiating a new object that implements nsISupports.
* Use this in your factory methods to allow for refcnt tracing.
* Note that you can only use this if you adhere to the no arguments
* constructor com policy (which you really should!).
* @param _result Where the new instance pointer is stored
* @param _type The type of object to call "new" with.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_NEWXPCOM(_result,_type) \
PR_BEGIN_MACRO \
_result = new _type(); \
nsTraceRefcnt::Create(_result, #_type, __FILE__, __LINE__); \
PR_END_MACRO
#else
#define NS_NEWXPCOM(_result,_type) \
_result = new _type()
#endif
/**
* Macro for deleting an object that implements nsISupports.
* Use this in your Release methods to allow for refcnt tracing.
* @param _ptr The object to delete.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_DELETEXPCOM(_ptr) \
PR_BEGIN_MACRO \
nsTraceRefcnt::Destroy((_ptr), __FILE__, __LINE__); \
delete (_ptr); \
PR_END_MACRO
#else
#define NS_DELETEXPCOM(_ptr) \
delete (_ptr)
#endif
/**
* Macro for adding a reference to an interface.
* @param _ptr The interface pointer.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_ADDREF(_ptr) \
((nsrefcnt) nsTraceRefcnt::AddRef((_ptr), (_ptr)->AddRef(), \
__FILE__, __LINE__))
#else
#define NS_ADDREF(_ptr) \
(_ptr)->AddRef()
#endif
/**
* Macro for adding a reference to this. This macro should be used
* because NS_ADDREF (when tracing) may require an ambiguous cast
* from the pointers primary type to nsISupports. This macro sidesteps
* that entire problem.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_ADDREF_THIS() \
((nsrefcnt) nsTraceRefcnt::AddRef(this, AddRef(), __FILE__, __LINE__))
#else
#define NS_ADDREF_THIS() \
AddRef()
#endif
/**
* Macro for adding a reference to an interface that checks for NULL.
* @param _ptr The interface pointer.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_IF_ADDREF(_ptr) \
((0 != (_ptr)) \
? ((nsrefcnt) nsTraceRefcnt::AddRef((_ptr), (_ptr)->AddRef(), __FILE__, \
__LINE__)) \
: 0)
#else
#define NS_IF_ADDREF(_ptr) \
((0 != (_ptr)) ? (_ptr)->AddRef() : 0)
#endif
/**
* Macro for releasing a reference to an interface.
*
* Note that when MOZ_TRACE_XPCOM_REFCNT is defined that the release will
* be done before the trace message is logged. If the reference count
* goes to zero and implementation of Release logs a message, the two
* messages will be logged out of order.
*
* @param _ptr The interface pointer.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_RELEASE(_ptr) \
PR_BEGIN_MACRO \
nsTraceRefcnt::Release((_ptr), (_ptr)->Release(), __FILE__, __LINE__); \
(_ptr) = 0; \
PR_END_MACRO
#else
#define NS_RELEASE(_ptr) \
PR_BEGIN_MACRO \
(_ptr)->Release(); \
(_ptr) = 0; \
PR_END_MACRO
#endif
/**
* Macro for releasing a reference to an interface.
*
* Note that when MOZ_TRACE_XPCOM_REFCNT is defined that the release will
* be done before the trace message is logged. If the reference count
* goes to zero and implementation of Release logs a message, the two
* messages will be logged out of order.
*
* @param _ptr The interface pointer.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_RELEASE_THIS() \
nsTraceRefcnt::Release(this, Release(), __FILE__, __LINE__)
#else
#define NS_RELEASE_THIS() \
Release()
#endif
/**
* Macro for releasing a reference to an interface, except that this
* macro preserves the return value from the underlying Release call.
* The interface pointer argument will only be NULLed if the reference count
* goes to zero.
*
* Note that when MOZ_TRACE_XPCOM_REFCNT is defined that the release will
* be done before the trace message is logged. If the reference count
* goes to zero and implementation of Release logs a message, the two
* messages will be logged out of order.
*
* @param _ptr The interface pointer.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_RELEASE2(_ptr, _result) \
PR_BEGIN_MACRO \
_result = ((nsrefcnt) nsTraceRefcnt::Release((_ptr), (_ptr)->Release(), \
__FILE__, __LINE__)); \
if (0 == (_result)) (_ptr) = 0; \
PR_END_MACRO
#else
#define NS_RELEASE2(_ptr, _result) \
PR_BEGIN_MACRO \
_result = (_ptr)->Release(); \
if (0 == (_result)) (_ptr) = 0; \
PR_END_MACRO
#endif
/**
* Macro for releasing a reference to an interface that checks for NULL;
*
* Note that when MOZ_TRACE_XPCOM_REFCNT is defined that the release will
* be done before the trace message is logged. If the reference count
* goes to zero and implementation of Release logs a message, the two
* messages will be logged out of order.
*
* @param _ptr The interface pointer.
*/
#ifdef MOZ_TRACE_XPCOM_REFCNT
#define NS_IF_RELEASE(_ptr) \
PR_BEGIN_MACRO \
if (_ptr) { \
(nsrefcnt) nsTraceRefcnt::Release((_ptr), (_ptr)->Release(), \
__FILE__, __LINE__); \
(_ptr) = 0; \
} \
PR_END_MACRO
#else
#define NS_IF_RELEASE(_ptr) \
PR_BEGIN_MACRO \
if (_ptr) { \
(_ptr)->Release(); \
(_ptr) = 0; \
} \
PR_END_MACRO
#endif
#ifdef MOZ_LOG_REFCNT
#define NS_LOG_ADDREF(_ptr, _refcnt, _file, _line) \
nsTraceRefcnt::LogAddRef((_ptr), (_refcnt), (_file), (_line))
#define NS_LOG_RELEASE(_ptr, _refcnt, _file, _line) \
nsTraceRefcnt::LogRelease((_ptr), (_refcnt), (_file), (_line))
#else
#define NS_LOG_ADDREF(_file, _line, _ptr, _refcnt)
#define NS_LOG_RELEASE(_file, _line, _ptr, _refcnt)
#endif
////////////////////////////////////////////////////////////////////////////////
// A type-safe interface for calling |QueryInterface()|. A similar implementation
// exists in "nsCOMPtr.h" for use with |nsCOMPtr|s.
extern "C++" {
// ...because some one is accidentally including this file inside an |extern "C"|
class nsISupports;
template <class T>
struct nsCOMTypeInfo
{
static const nsIID& GetIID() { return T::GetIID(); }
};
#ifdef NSCAP_FEATURE_HIDE_NSISUPPORTS_GETIID
template <>
struct nsCOMTypeInfo<nsISupports>
{
static const nsIID& GetIID() { static nsIID iid = NS_ISUPPORTS_IID; return iid; }
};
#endif
#define NS_GET_IID(T) nsCOMTypeInfo<T>::GetIID()
template <class DestinationType>
inline
nsresult
CallQueryInterface( nsISupports* aSource, 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(nsCOMTypeInfo<DestinationType>::GetIID(), (void**)aDestination);
}
} // extern "C++"
////////////////////////////////////////////////////////////////////////////////
#endif /* __nsISupportsUtils_h */