DOS Fn 29H: Parse Filename

                                                         Compatibility: 1.0+ 
 Expects: AH    29H
          AL    bit-flags to select parsing options (see below)
          DS:SI address of source text line to parse
          ES:DI address of buffer to hold resulting unopened FCB
          ──────────────────────────────────────────────────────────────────
 Returns: AL    0    if result FCB has no wildcard characters  
                1    if result FCB does contain wildcards▲
                0ffH if invalid drive ID in filespec
          DS:SI updated: points to the character just past the filename
          ES:DI preserved: points to the unopened FCB
          ──────────────────────────────────────────────────────────────────
    Info: Creates an unopened FCB from a text line or command parameter.
          The text starting at DS:SI is parsed for a filespec in the format
          D:FILENAME.EXT and the buffer at ES:DI is filled in as a
          properly-formatted, unopened FCB.

     ═══► This Fn is NOT useful for a text line containing a pathname.
          Basically, this is a quick way to skip leading spaces, upshift
          and remove the dot (.) from a filename input from the keyboard.
          It converts * into a series of ?s and it allows you to pre-set a
          default in the destination FCB (e.g., extension = "WKS").

          The parsing action depends upon these bit flags in AL:
          ╓7┬6┬5┬4┬3┬2┬1┬0╖
          ║0 0 0 0│ │ │ │ ║
          ╙─┴─┴─┴─┴╥┴╥┴╥┴╥╜ bit                                  mask value
                   ║ ║ ║ ╚═► 0: 1=scan off leading separators     (a | 01H)
                   ║ ║ ╚═══► 1: 1=use FCB drive byte as a default (a | 02H)
                   ║ ╚═════► 2: 1=use FCB filename as a default   (a | 04H)
                   ╚═══════► 3: 1=use FCB extension as a default  (a | 08H)

See Also: Fn 60H (Get Truename)
          FCB File I/O
          DOS Functions
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