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 // Created on: 2007-09-04
 // Created by: Andrey BETENEV
 // Copyright (c) 2007-2014 OPEN CASCADE SAS
 //
 // This file is part of Open CASCADE Technology software library.
 //
 // This library is free software; you can redistribute it and/or modify it under
 // the terms of the GNU Lesser General Public License version 2.1 as published
 // by the Free Software Foundation, with special exception defined in the file
 // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
 // distribution for complete text of the license and disclaimer of any warranty.
 //
 // Alternatively, this file may be used under the terms of Open CASCADE
 // commercial license or contractual agreement.
 
 //! @file
 //! Implementation of some atomic operations (elementary operations
 //! with data that cannot be interrupted by parallel threads in the
 //! multithread process) on various platforms
 //!
 //! By the moment, only operations necessary for reference counter
 //! in Standard_Transient objects are implemented.
 //!
 //! This is preferred to use fixed size types "int32_t" / "int64_t" for
 //! correct function declarations however we leave "int" assuming it is 32bits for now.
 
 #ifndef _Standard_Atomic_HeaderFile
 #define _Standard_Atomic_HeaderFile
 
 //! Increments atomically integer variable pointed by theValue
 //! and returns resulting incremented value.
 inline int Standard_Atomic_Increment (volatile int* theValue);
 
 //! Decrements atomically integer variable pointed by theValue
 //! and returns resulting decremented value.
 inline int Standard_Atomic_Decrement (volatile int* theValue);
 
 //! Perform an atomic compare and swap.
 //! That is, if the current value of *theValue is theOldValue, then write theNewValue into *theValue.
 //! @param theValue    pointer to variable to modify
 //! @param theOldValue expected value to perform modification
 //! @param theNewValue new value to set in case if *theValue was equal to theOldValue
 //! @return TRUE if theNewValue has been set to *theValue
 inline bool Standard_Atomic_CompareAndSwap (volatile int* theValue, int theOldValue, int theNewValue);
 
 // Platform-dependent implementation
 #if defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4) || defined(__EMSCRIPTEN__)
 // gcc explicitly defines the macros __GCC_HAVE_SYNC_COMPARE_AND_SWAP_*
 // starting with version 4.4+, although built-in functions
 // are available since 4.1.x. However unless __GCC_HAVE_SYNC_COMPARE_AND_SWAP_*
 // are defined, linking may fail without specifying -march option when
 // building for 32bit architecture on 64bit (using -m32 option). To avoid
 // making -march mandatory, check for __GCC_HAVE_SYNC_COMPARE_AND_SWAP_* is
 // enforced.
 
 int Standard_Atomic_Increment (volatile int* theValue)
 {
   return __sync_add_and_fetch (theValue, 1);
 }
 
 int Standard_Atomic_Decrement (volatile int* theValue)
 {
   return __sync_sub_and_fetch (theValue, 1);
 }
 
 bool Standard_Atomic_CompareAndSwap (volatile int* theValue, int theOldValue, int theNewValue)
 {
   return __sync_val_compare_and_swap (theValue, theOldValue, theNewValue) == theOldValue;
 }
 
 #elif defined(_WIN32)
 extern "C" {
   long _InterlockedIncrement (volatile long* lpAddend);
   long _InterlockedDecrement (volatile long* lpAddend);
   long _InterlockedCompareExchange (long volatile* Destination, long Exchange, long Comparand);
 }
 
 #if defined(_MSC_VER) && ! defined(__INTEL_COMPILER)
   // force intrinsic instead of WinAPI calls
   #pragma intrinsic (_InterlockedIncrement)
   #pragma intrinsic (_InterlockedDecrement)
   #pragma intrinsic (_InterlockedCompareExchange)
 #endif
 
 // WinAPI function or MSVC intrinsic
 // Note that we safely cast int* to long*, as they have same size and endian-ness
 
 int Standard_Atomic_Increment (volatile int* theValue)
 {
   return _InterlockedIncrement (reinterpret_cast<volatile long*>(theValue));
 }
 
 int Standard_Atomic_Decrement (volatile int* theValue)
 {
   return _InterlockedDecrement (reinterpret_cast<volatile long*>(theValue));
 }
 
 bool Standard_Atomic_CompareAndSwap (volatile int* theValue, int theOldValue, int theNewValue)
 {
   return _InterlockedCompareExchange (reinterpret_cast<volatile long*>(theValue), theNewValue, theOldValue) == theOldValue;
 }
 
 #elif defined(__APPLE__)
 // use atomic operations provided by MacOS
 
 #include <libkern/OSAtomic.h>
 
 int Standard_Atomic_Increment (volatile int* theValue)
 {
   return OSAtomicIncrement32Barrier (theValue);
 }
 
 int Standard_Atomic_Decrement (volatile int* theValue)
 {
   return OSAtomicDecrement32Barrier (theValue);
 }
 
 bool Standard_Atomic_CompareAndSwap (volatile int* theValue, int theOldValue, int theNewValue)
 {
   return OSAtomicCompareAndSwapInt (theOldValue, theNewValue, theValue);
 }
 
 #elif defined(__ANDROID__)
 
 // Atomic operations that were exported by the C library didn't
 // provide any memory barriers, which created potential issues on
 // multi-core devices. Starting from ndk version r7b they are defined as
 // inlined calls to GCC sync builtins, which always provide a full barrier.
 // It is strongly recommended to use newer versions of ndk.
 #include <sys/atomics.h>
 
 int Standard_Atomic_Increment (volatile int* theValue)
 {
   return __atomic_inc (theValue) + 1; // analog of __sync_fetch_and_add
 }
 
 int Standard_Atomic_Decrement (volatile int* theValue)
 {
   return __atomic_dec (theValue) - 1; // analog of __sync_fetch_and_sub
 }
 
 bool Standard_Atomic_CompareAndSwap (volatile int* theValue, int theOldValue, int theNewValue)
 {
   return __atomic_cmpxchg (theOldValue, theNewValue, theValue) == 0;
 }
 
 #else
 
 #ifndef IGNORE_NO_ATOMICS
   #error "Atomic operation isn't implemented for current platform!"
 #endif
 int Standard_Atomic_Increment (volatile int* theValue)
 {
   return ++(*theValue);
 }
 
 int Standard_Atomic_Decrement (volatile int* theValue)
 {
   return --(*theValue);
 }
 
 bool Standard_Atomic_CompareAndSwap (volatile int* theValue, int theOldValue, int theNewValue)
 {
   if (*theValue == theOldValue)
   {
     *theValue = theNewValue;
     return true;
   }
   return false;
 }
 
 #endif
 
 #endif //_Standard_Atomic_HeaderFile

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