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/**********************************************************************
* $Id: cpl_atomic_ops.h 19884 2010-06-17 22:01:19Z rouault $
*
* Name: cpl_atomic_ops.h
* Project: CPL - Common Portability Library
* Purpose: Atomic operation functions.
* Author: Even Rouault, <even dot rouault at mines dash paris dot org>
*
**********************************************************************
* Copyright (c) 2009, Even Rouault, <even dot rouault at mines dash paris dot org>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
****************************************************************************/
#ifndef _CPL_ATOMIC_OPS_INCLUDED
#define _CPL_ATOMIC_OPS_INCLUDED
#include "cpl_port.h"
CPL_C_START
/** Add a value to a pointed integer in a thread and SMP-safe way
* and return the resulting value of the operation.
*
* This function, which in most cases is implemented by a few
* efficient machine instructions, guarantees that the value pointed
* by ptr will be incremented in a thread and SMP-safe way.
* The variables for this function must be aligned on a 32-bit boundary.
*
* Depending on the platforms, this function can also act as a
* memory barrier, but this should not be assumed.
*
* Current platforms/architectures where an efficient implementation
* exists are MacOSX, MS Windows, i386/x86_64 with GCC and platforms
* supported by GCC 4.1 or higher. For other platforms supporting
* the pthread library, and when GDAL is configured with thread-support,
* the atomicity will be done with a mutex, but with
* reduced efficiently. For the remaining platforms, a simple addition
* with no locking will be done...
*
* @param ptr a pointer to an integer to increment
* @param increment the amount to add to the pointed integer
* @return the pointed value AFTER the result of the addition
*/
int CPL_DLL CPLAtomicAdd(volatile int* ptr, int increment);
/** Increment of 1 the pointed integer in a thread and SMP-safe way
* and return the resulting value of the operation.
*
* @see CPLAtomicAdd for the details and guarantees of this atomic
* operation
*
* @param ptr a pointer to an integer to increment
* @return the pointed value AFTER the opeation: *ptr + 1
*/
#ifdef HAS_CPL_INLINE
CPL_INLINE int CPLAtomicInc(volatile int* ptr)
{
return CPLAtomicAdd(ptr, 1);
}
#else
int CPL_DLL CPLAtomicInc(volatile int* ptr);
#endif
/** Decrement of 1 the pointed integer in a thread and SMP-safe way
* and return the resulting value of the operation.
*
* @see CPLAtomicAdd for the details and guarantees of this atomic
* operation
*
* @param ptr a pointer to an integer to decrement
* @return the pointed value AFTER the opeation: *ptr - 1
*/
#ifdef HAS_CPL_INLINE
CPL_INLINE int CPLAtomicDec(volatile int* ptr)
{
return CPLAtomicAdd(ptr, -1);
}
#else
int CPL_DLL CPLAtomicDec(volatile int* ptr);
#endif
CPL_C_END
#endif /* _CPL_ATOMIC_OPS_INCLUDED */
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