InterlockedCompareExchange

PVOID
InterlockedCompareExchange(
IN OUT PVOID *Destination,
IN PVOID Exchange,
IN PVOID Comperand
);

InterlockedCompareExchange compares a pointer value (Comperand) with a destination pointer value (Destination). If the values are equal, then a third pointer value (Exchange) is stored in the destination. Otherwise, no operation is performed. The compare and exchange operations are performed in an atomic operation.

Parameters

Destination: Points to a destination value that will be compared and possibly replaced.
Exchange: Points to the value that will replace the destination value if the comparison results in equality.
Comperand: Points to the value with which the destination value will be compared.

Return Value

InterlockedCompareExchange returns the original destination value.

Comments

InterlockedCompareExchange provides an atomic way to test a value and update it if the test passes. This routine is implemented inline by the compiler when appropriate and possible. It does not require a spin lock and can therefore be safely used on pageable data.

The InterlockedCompareExchange routine is atomic only with respect to other InterlockedXxx calls.

Callers of InterlockedCompareExchange run at any IRQL.