hDevice (HFILE) - input
pszDeviceName (PSZ) - input
Port name being written to.
pfnPdWrite (PFN) - input
pfnBaseProtWrite (PFN) - input
This is NULL unless the protocol converter is an extension to the base protocol converter. If not NULL, the extension protocol converter can call the base converter at this address to let the base converter process the command.
pchData (PVOID) - input
cbInData (ULONG) - input
pcbWritten (PULONG) - output
This value can be updated even when an unsuccessful return code is given, if some of the data was sent to the printer.
rc (ULONG) - returns
Note: *pcbWritten is updated with the number of bytes sent to the printer. If all bytes were not written, it should be considered an error.