Defined as:

struct CFStreamClientContext { CFIndex version; void info; void *(retain)(void info); void (release)(void info); CFStringRef (copyDescription)(void *info); } CFStreamClientContext;

In the “Working with Streams” section of the CFNetwork guide, the example uses custom function pointers as listed below:

CFStreamClientContext myContext = {0, myPtr, myRetain, myRelease, myCopyDesc};

It’s much easier, and just as valid to use the built in CoreFoundation functions:

CFStreamClientContext myContext = { 0, self, (void ()(void info))CFRetain, (void ()(void info))CFRelease, (CFStringRef ()(void *info))CFCopyDescription };