Return
codes indicating success or type of failure. If the function succeeds,
the number of bytes copied is returned. A NULL is returned for a failure.
A call to mmioGetLastError might
return one of the following errors:
MMIOERR_INVALID_PARAMETER
For this function, a
NULL pmmcfinfo is invalid. cBytes must be greater than 0.
MMIOERR_READ_ONLY_FILE
File
not opened in write mode.
MMIOERR_INTERNAL_SYSTEM
The operation failed due to an internal system
error.