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/**
* @file llrefcount.h
* @brief Base class for reference counted objects for use with LLPointer
*
* $LicenseInfo:firstyear=2002&license=viewerlgpl$
* 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 LLREFCOUNT_H
#define LLREFCOUNT_H
#include <boost/noncopyable.hpp>
#include <boost/intrusive_ptr.hpp>
#include "llatomic.h"
class LLMutex;
//----------------------------------------------------------------------------
// RefCount objects should generally only be accessed by way of LLPointer<>'s
// see llthread.h for LLThreadSafeRefCount
//----------------------------------------------------------------------------
//nonsense but recognizable value for freed LLRefCount (aids in debugging)
#define LL_REFCOUNT_FREE 1234567890
extern const S32 gMaxRefCount;
class LL_COMMON_API LLRefCount
{
protected:
LLRefCount(const LLRefCount& other);
LLRefCount& operator=(const LLRefCount&);
virtual ~LLRefCount(); // use unref()
public:
LLRefCount();
inline void ref() const
{
llassert(mRef != LL_REFCOUNT_FREE); // object is deleted
mRef++;
llassert(mRef < gMaxRefCount); // ref count excessive, likely memory leak
}
inline S32 unref() const
{
llassert(mRef != LL_REFCOUNT_FREE); // object is deleted
llassert(mRef > 0); // ref count below 1, likely corrupted
if (0 == --mRef)
{
mRef = LL_REFCOUNT_FREE; // set to nonsense yet recognizable value to aid in debugging
delete this;
return 0;
}
return mRef;
}
//NOTE: when passing around a const LLRefCount object, this can return different results
// at different types, since mRef is mutable
S32 getNumRefs() const
{
return mRef;
}
private:
mutable S32 mRef;
};
//============================================================================
// see llmemory.h for LLPointer<> definition
class LL_COMMON_API LLThreadSafeRefCount
{
protected:
virtual ~LLThreadSafeRefCount(); // use unref()
public:
LLThreadSafeRefCount();
LLThreadSafeRefCount(const LLThreadSafeRefCount&);
LLThreadSafeRefCount& operator=(const LLThreadSafeRefCount& ref)
{
mRef = 0;
return *this;
}
void ref()
{
mRef++;
}
void unref()
{
llassert(mRef >= 1);
if ((--mRef) == 0)
{
// If we hit zero, the caller should be the only smart pointer owning the object and we can delete it.
// It is technically possible for a vanilla pointer to mess this up, or another thread to
// jump in, find this object, create another smart pointer and end up dangling, but if
// the code is that bad and not thread-safe, it's trouble already.
delete this;
}
}
S32 getNumRefs() const
{
const S32 currentVal = mRef.CurrentValue();
return currentVal;
}
private:
LLAtomicS32 mRef;
};
/**
* intrusive pointer support for LLThreadSafeRefCount
* this allows you to use boost::intrusive_ptr with any LLThreadSafeRefCount-derived type
*/
inline void intrusive_ptr_add_ref(LLThreadSafeRefCount* p)
{
p->ref();
}
inline void intrusive_ptr_release(LLThreadSafeRefCount* p)
{
p->unref();
}
/**
* intrusive pointer support
* this allows you to use boost::intrusive_ptr with any LLRefCount-derived type
*/
inline void intrusive_ptr_add_ref(LLRefCount* p)
{
p->ref();
}
inline void intrusive_ptr_release(LLRefCount* p)
{
p->unref();
}
#endif
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