Legacy Document

Inside Macintosh: Networking With Open Transport / Part 2 - Open Transport Reference

Chapter 27 - Utilities Reference / Functions

Atomic Operations /

OTAtomicAdd16

Atomically adds a 16-bit value to a memory location.

C INTERFACE

SInt16 OTAtomicAdd16(SInt32 toAdd,
                     SInt16* where)

C++ INTERFACE

None. C++ applications use the C interface to this function.

PARAMETERS

toAdd

A signed 16-bit value to add to the value referenced by the where parameter.

where

A pointer to a signed 16-bit value that is added to the value specified by the parameter toAdd.

function result

The sum of the values specified by the function's parameters.

DISCUSSION

This function atomically adds the least significat 16 bits of toAdd to the value referenced by the where parameter and returns the result. It also stores the result in the location referenced by the where parameter

You can use this function to subtract from the toAdd value from the value referenced by the where parameter by reversing the sign of toAdd.

WARNING

The pointer where must be at an address where the second byte of the 16 bit value is not in a different 4-byte cell than the first byte (i.e. (where % 4) != 3).

Use the OTAtomicAdd32 function to add two 32-bit values.

Use the OTAtomicAdd8 function to add two 8-bit values.