17. FILE_OPENDIR

*------------------------------------------------------------------------------
* NAME          FILE_OPENDIR
*------------------------------------------------------------------------------
* DEPENDENCY    FILE_OPEN
* PURPOSE       To open a file like 'OPEN_DIR #3,devicename'
* DESCRIPTION   Opens a file in mode 4 (directory) The filename is
*               passed in A0 (a pointer to the name). The current job assumes
*               ownership of the channel. May need a TRAP #4 before calling if
*               the filename is relative A6 when called. (SuperBasic).
* INPUTS :
*               A0.L = Pointer to filename
* OUTPUTS :
*               A0.L = Channel id.
*               D0 = Error code
*               Z flag set if no errors, unset otherwise.
*------------------------------------------------------------------------------
file_opendir    movem.l d1-d3,-(a7)     ; Those workers need saving
                moveq   #4,d3           ; Directory mode
                bra     fo_params       ; Do the rest via FILE_OPEN