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InterlockedCompareExchange128 function

Performs an atomic compare-and-exchange operation on the specified values. The function compares two specified 128-bit values and exchanges with another 128-bit value based on the outcome of the comparison.

To operate on 16-bit values, use the InterlockedCompareExchange16 function.

To operate on 32-bit values, use the InterlockedCompareExchange function.

To operate on 64-bit values, use the InterlockedCompareExchange64 function.

Syntax

C++


unsigned char __cdecl InterlockedCompareExchange128(
  _Inout_  LONGLONG volatile *Destination,
  _In_     LONGLONG ExchangeHigh,
  _In_     LONGLONG ExchangeLow,
  _Inout_  LONGLONG *ComparandResult
);

Parameters

Destination [in, out]: A pointer to the destination value. This parameter is an array of two 64-bit integers considered as a 128-bit field.
ExchangeHigh [in]: The high part of the exchange value.
ExchangeLow [in]: The low part of the exchange value.
ComparandResult [in, out]: The value to compare to. This parameter is an array of two 64-bit integers considered as a 128-bit field.

Return value

The function returns 1 if ComparandResult equals the original value of the Destination parameter, or 0 if ComparandResult does not equal the original value of the Destination parameter.

Remarks

The function compares the Destination value with the ComparandResult value:

If the Destination value is equal to the ComparandResult value, the ExchangeHigh and ExchangeLow values are stored in the array specified by Destination, and also in the array specified by ComparandResult.
Otherwise, the ExchangeHigh and ExchangeLow values are only stored in the array specified by ComparandResult.

The parameters for this function must be aligned on a 16-byte boundary; otherwise, the function will behave unpredictably on x64 systems. See _aligned_malloc.

The interlocked functions provide a simple mechanism for synchronizing access to a variable that is shared by multiple threads. This function is atomic with respect to calls to other interlocked functions.

This function is only available on x64-based systems, and it is implemented using a compiler intrinsic. For more information, see the WinBase.h header file and _InterlockedCompareExchange128.

This function generates a full memory barrier (or fence) to ensure that memory operations are completed in order.

Requirements

Minimum supported client	Windows 8 [desktop apps only]
Minimum supported server	Windows Server 2012 [desktop apps only]
Header	Winnt.h (include Windows.h)

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