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84aa0abd27
We have blatant C++ code later on in the file; whatever C file(s) were including nsISupportsUtils.h are now a distant memory.
138 lines
5.0 KiB
C++
138 lines
5.0 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsISupportsUtils_h__
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#define nsISupportsUtils_h__
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#include "nscore.h"
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#include "nsISupportsBase.h"
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#include "nsError.h"
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#include "nsDebug.h"
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#include "nsISupportsImpl.h"
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#include "mozilla/TypeTraits.h"
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/**
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* Macro for adding a reference to an interface.
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* @param _ptr The interface pointer.
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*/
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#define NS_ADDREF(_ptr) \
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(_ptr)->AddRef()
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/**
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* Macro for adding a reference to this. This macro should be used
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* because NS_ADDREF (when tracing) may require an ambiguous cast
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* from the pointers primary type to nsISupports. This macro sidesteps
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* that entire problem.
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*/
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#define NS_ADDREF_THIS() \
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AddRef()
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// Making this a |inline| |template| allows |aExpr| to be evaluated only once,
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// yet still denies you the ability to |AddRef()| an |nsCOMPtr|.
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template<class T>
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inline void
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ns_if_addref(T aExpr)
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{
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if (aExpr) {
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aExpr->AddRef();
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}
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}
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/**
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* Macro for adding a reference to an interface that checks for nullptr.
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* @param _expr The interface pointer.
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*/
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#define NS_IF_ADDREF(_expr) ns_if_addref(_expr)
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/*
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* Given these declarations, it explicitly OK and efficient to end a `getter' with:
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*
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* NS_IF_ADDREF(*result = mThing);
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*
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* even if |mThing| is an |nsCOMPtr|. If |mThing| is an |nsCOMPtr|, however, it is still
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* _illegal_ to say |NS_IF_ADDREF(mThing)|.
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*/
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/**
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* Macro for releasing a reference to an interface.
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* @param _ptr The interface pointer.
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*/
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#define NS_RELEASE(_ptr) \
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do { \
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(_ptr)->Release(); \
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(_ptr) = 0; \
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} while (0)
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/**
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* Macro for releasing a reference to this interface.
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*/
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#define NS_RELEASE_THIS() \
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Release()
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/**
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* Macro for releasing a reference to an interface, except that this
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* macro preserves the return value from the underlying Release call.
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* The interface pointer argument will only be NULLed if the reference count
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* goes to zero.
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*
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* @param _ptr The interface pointer.
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* @param _rc The reference count.
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*/
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#define NS_RELEASE2(_ptr, _rc) \
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do { \
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_rc = (_ptr)->Release(); \
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if (0 == (_rc)) (_ptr) = 0; \
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} while (0)
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/**
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* Macro for releasing a reference to an interface that checks for nullptr;
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* @param _ptr The interface pointer.
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*/
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#define NS_IF_RELEASE(_ptr) \
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do { \
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if (_ptr) { \
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(_ptr)->Release(); \
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(_ptr) = 0; \
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} \
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} while (0)
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/*
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* Often you have to cast an implementation pointer, e.g., |this|, to an
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* |nsISupports*|, but because you have multiple inheritance, a simple cast
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* is ambiguous. One could simply say, e.g., (given a base |nsIBase|),
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* |static_cast<nsIBase*>(this)|; but that disguises the fact that what
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* you are really doing is disambiguating the |nsISupports|. You could make
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* that more obvious with a double cast, e.g., |static_cast<nsISupports*>
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(* static_cast<nsIBase*>(this))|, but that is bulky and harder to read...
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*
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* The following macro is clean, short, and obvious. In the example above,
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* you would use it like this: |NS_ISUPPORTS_CAST(nsIBase*, this)|.
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*/
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#define NS_ISUPPORTS_CAST(__unambiguousBase, __expr) \
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static_cast<nsISupports*>(static_cast<__unambiguousBase>(__expr))
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// a type-safe shortcut for calling the |QueryInterface()| member function
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template<class T, class DestinationType>
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inline nsresult
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CallQueryInterface(T* aSource, DestinationType** aDestination)
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{
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// We permit nsISupports-to-nsISupports here so that one can still obtain
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// the canonical nsISupports pointer with CallQueryInterface.
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static_assert(!mozilla::IsSame<T, DestinationType>::value ||
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mozilla::IsSame<DestinationType, nsISupports>::value,
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"don't use CallQueryInterface for compile-time-determinable casts");
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NS_PRECONDITION(aSource, "null parameter");
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NS_PRECONDITION(aDestination, "null parameter");
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return aSource->QueryInterface(NS_GET_TEMPLATE_IID(DestinationType),
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reinterpret_cast<void**>(aDestination));
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}
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#endif /* __nsISupportsUtils_h */
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