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Diffstat (limited to 'indra/llcommon/llsafehandle.h')
| -rw-r--r-- | indra/llcommon/llsafehandle.h | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/indra/llcommon/llsafehandle.h b/indra/llcommon/llsafehandle.h new file mode 100644 index 0000000000..8d52d9bb15 --- /dev/null +++ b/indra/llcommon/llsafehandle.h @@ -0,0 +1,162 @@ +/** + * @file llsafehandle.h + * @brief Reference-counted object where Object() is valid, not NULL. + * + * $LicenseInfo:firstyear=2002&license=viewerlgpl$ + * Second Life Viewer Source Code + * Copyright (C) 2010, Linden Research, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; + * version 2.1 of the License only. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA + * $/LicenseInfo$ + */ +#ifndef LLSAFEHANDLE_H +#define LLSAFEHANDLE_H + +#include "llerror.h" // *TODO: consider eliminating this + +// Expands LLPointer to return a pointer to a special instance of class Type instead of NULL. +// This is useful in instances where operations on NULL pointers are semantically safe and/or +// when error checking occurs at a different granularity or in a different part of the code +// than when referencing an object via a LLSafeHandle. + +template <class Type> +class LLSafeHandle +{ +public: + LLSafeHandle() : + mPointer(NULL) + { + } + + LLSafeHandle(Type* ptr) : + mPointer(NULL) + { + assign(ptr); + } + + LLSafeHandle(const LLSafeHandle<Type>& ptr) : + mPointer(NULL) + { + assign(ptr.mPointer); + } + + // support conversion up the type hierarchy. See Item 45 in Effective C++, 3rd Ed. + template<typename Subclass> + LLSafeHandle(const LLSafeHandle<Subclass>& ptr) : + mPointer(NULL) + { + assign(ptr.get()); + } + + ~LLSafeHandle() + { + unref(); + } + + const Type* operator->() const { return nonNull(mPointer); } + Type* operator->() { return nonNull(mPointer); } + + Type* get() const { return mPointer; } + void clear() { assign(NULL); } + // we disallow these operations as they expose our null objects to direct manipulation + // and bypass the reference counting semantics + //const Type& operator*() const { return *nonNull(mPointer); } + //Type& operator*() { return *nonNull(mPointer); } + + operator BOOL() const { return mPointer != NULL; } + operator bool() const { return mPointer != NULL; } + bool operator!() const { return mPointer == NULL; } + bool isNull() const { return mPointer == NULL; } + bool notNull() const { return mPointer != NULL; } + + + operator Type*() const { return mPointer; } + operator const Type*() const { return mPointer; } + bool operator !=(Type* ptr) const { return (mPointer != ptr); } + bool operator ==(Type* ptr) const { return (mPointer == ptr); } + bool operator ==(const LLSafeHandle<Type>& ptr) const { return (mPointer == ptr.mPointer); } + bool operator < (const LLSafeHandle<Type>& ptr) const { return (mPointer < ptr.mPointer); } + bool operator > (const LLSafeHandle<Type>& ptr) const { return (mPointer > ptr.mPointer); } + + LLSafeHandle<Type>& operator =(Type* ptr) + { + assign(ptr); + return *this; + } + + LLSafeHandle<Type>& operator =(const LLSafeHandle<Type>& ptr) + { + assign(ptr.mPointer); + return *this; + } + + // support assignment up the type hierarchy. See Item 45 in Effective C++, 3rd Ed. + template<typename Subclass> + LLSafeHandle<Type>& operator =(const LLSafeHandle<Subclass>& ptr) + { + assign(ptr.get()); + return *this; + } + +public: + typedef Type* (*NullFunc)(); + static const NullFunc sNullFunc; + +protected: + void ref() + { + if (mPointer) + { + mPointer->ref(); + } + } + + void unref() + { + if (mPointer) + { + Type *tempp = mPointer; + mPointer = NULL; + tempp->unref(); + if (mPointer != NULL) + { + llwarns << "Unreference did assignment to non-NULL because of destructor" << llendl; + unref(); + } + } + } + + void assign(Type* ptr) + { + if( mPointer != ptr ) + { + unref(); + mPointer = ptr; + ref(); + } + } + + static Type* nonNull(Type* ptr) + { + return ptr == NULL ? sNullFunc() : ptr; + } + +protected: + Type* mPointer; +}; + +#endif |