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/** @file
* IPRT - Classes for Scope-based Locking.
*/
/*
* Copyright (C) 2007-2022 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, in version 3 of the
* License.
*
* This program 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses>.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
* in the VirtualBox distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*
* SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
*/
#ifndef IPRT_INCLUDED_cpp_lock_h
#define IPRT_INCLUDED_cpp_lock_h
#ifndef RT_WITHOUT_PRAGMA_ONCE
# pragma once
#endif
#include <iprt/critsect.h>
#ifdef RT_LOCK_STRICT
# include <iprt/lockvalidator.h>
#endif
RT_C_DECLS_BEGIN
/** @defgroup grp_rt_cpp_lock C++ Scope-based Locking
* @ingroup grp_rt_cpp
* @{
*/
class RTCLock;
/**
* The mutex lock.
*
* This is used as an object data member if the intention is to lock
* a single object. This can also be used statically, initialized in
* a global variable, for class wide purposes.
*
* This is best used together with RTCLock.
*/
class RTCLockMtx
{
friend class RTCLock;
private:
RTCRITSECT mMtx;
public:
RTCLockMtx()
{
#ifdef RT_LOCK_STRICT_ORDER
RTCritSectInitEx(&mMtx, 0 /*fFlags*/,
RTLockValidatorClassCreateUnique(RT_SRC_POS, NULL),
RTLOCKVAL_SUB_CLASS_NONE, NULL);
#else
RTCritSectInit(&mMtx);
#endif
}
/** Use to when creating locks that belongs in the same "class". */
RTCLockMtx(RT_SRC_POS_DECL, uint32_t uSubClass = RTLOCKVAL_SUB_CLASS_NONE)
{
#ifdef RT_LOCK_STRICT_ORDER
RTCritSectInitEx(&mMtx, 0 /*fFlags*/,
RTLockValidatorClassForSrcPos(RT_SRC_POS_ARGS, NULL),
uSubClass, NULL);
#else
NOREF(uSubClass);
RTCritSectInit(&mMtx);
RT_SRC_POS_NOREF();
#endif
}
~RTCLockMtx()
{
RTCritSectDelete(&mMtx);
}
/* lock() and unlock() are private so that only friend RTCLock can access
them. */
private:
inline void lock()
{
RTCritSectEnter(&mMtx);
}
inline void unlock()
{
RTCritSectLeave(&mMtx);
}
};
/**
* The stack object for automatic locking and unlocking.
*
* This is a helper class for automatic locks, to simplify requesting a
* RTCLockMtx and to not forget releasing it. To request a RTCLockMtx, simply
* create an instance of RTCLock on the stack and pass the mutex to it:
*
* @code
extern RTCLockMtx gMtx; // wherever this is
...
if (...)
{
RTCLock lock(gMtx);
... // do stuff
// when lock goes out of scope, destructor releases the mutex
}
@endcode
*
* You can also explicitly release the mutex by calling RTCLock::release().
* This might be helpful if the lock doesn't go out of scope early enough
* for your mutex to be released.
*/
class RTCLock
{
private:
/** Reference to the lock we're holding. */
RTCLockMtx &m_rMtx;
/** Whether we're currently holding the lock of if it was already
* explictily released by the release() method. */
bool m_fLocked;
public:
RTCLock(RTCLockMtx &a_rMtx)
: m_rMtx(a_rMtx)
{
m_rMtx.lock();
m_fLocked = true;
}
~RTCLock()
{
if (m_fLocked)
m_rMtx.unlock();
}
inline void release()
{
if (m_fLocked)
{
m_rMtx.unlock();
m_fLocked = false;
}
}
};
/** @} */
RT_C_DECLS_END
#endif /* !IPRT_INCLUDED_cpp_lock_h */
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