The name of the file to open. If the fccIOProc
field of MMIOINFO is NULL,
mmioOpen looks at the pszFileName parameter to figure out what kind
of file to open, as follows:
If the pszFileName parameter does not contain
a plus (+), the name is assumed to be that of a DOS file, which is opened
using the file system file open process.
If the file name is of the form ABC.EXT+ELEMENTNAME,
the extension EXT is assumed to identify an installed I/O procedure that
is called to perform I/O on the file (see mmioInstallIOProc).
If the extension is BND, the system-provided BND I/O procedure processes
the open. Note also that ELEMENTNAME could be of the form ABC.EXT followed
by a plus sign (+). Parsing of the file name is done from right to left,
so the first I/O procedure called belongs to the rightmost extension name
that is followed by the +. The I/O procedure must be already installed
and be able to further parse the file name, if required. The trailing separator
character is stripped off by mmioOpen, and is not passed to the I/O procedure.
If the pszFileName parameter is NULL, then
the aulInfo field of MMIOINFO
contains the DOS file handle, and I/O is performed on that file handle.
The MMIO offset is the same as the DOS offset when mmioOpen is called.
The pszFileName parameter cannot be longer
than 260 bytes, including the terminating NULL, for a fully-qualified path
name, or 256 bytes for an individual component name, including the terminating
NULL.