InterlockedExchange

The InterlockedExchange function atomically exchanges a pair of values. The function prevents more than one thread from using the same variable simultaneously.

If you are exchanging pointer values, this function has been superseded by the InterlockedExchangePointer function.

LONG InterlockedExchange(
  LPLONG Target, // value to exchange
  LONG Value     // new value
);

Parameters

Target

[in/out] Pointer to the value to exchange. The function sets this variable to Value, and returns its prior value.

Value

[in] Specifies a new value for the variable pointed to by Target.

Return Values

The function returns the initial value pointed to by Target.

Remarks

The functions InterlockedExchange, InterlockedCompareExchange, InterlockedDecrement, InterlockedExchangeAdd, and InterlockedIncrement provide a simple mechanism for synchronizing access to a variable that is shared by multiple threads. The threads of different processes can use this mechanism if the variable is in shared memory.

The variable pointed to by the Target parameter must be aligned on a 32-bit boundary; otherwise, this function will fail on multiprocessor x86 systems and any non-x86 systems.

Requirements

  Windows NT/2000: Requires Windows NT 3.5 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Declared in Winbase.h; include Windows.h.
  Library: Use Kernel32.lib.

See Also

Synchronization Overview, Synchronization Functions, Interlocked Variable Access, InterlockedCompareExchange, InterlockedDecrement, InterlockedExchangeAdd, InterlockedExchangePointer, InterlockedIncrement