This function regards the following as separator characters:Parses a text string into the various fields of a file control block (FCB).
Call with:
AH = 29H
AL = flags to control parsing
Bit 3 = 1 if extension field in FCB will be
modified only if an extension is
specified in the string being parsed.
= 0 if extension field in FCB will be
modified regardless; if no extension is
present in the parsed string, FCB
extension is set to ASCII blanks.
Bit 2 = 1 if filename field in FCB will be
modified only if a filename is
specified in the string being parsed.
= 0 if filename field in FCB will be
modified regardless; if no filename is
present in the parsed string, FCB
filename is set to ASCII blanks.
Bit 1 = 1 if drive ID byte in FCB will be
modified only if a drive was specified
in the string being parsed.
= 0 if the drive ID byte in FCB will be
modified regardless; if no drive
specifier is present in the parsed
string, FCB drive-code field is set to
0 (default).
Bit 0 = 1 if leading separators will be scanned
off (ignored).
= 0 if leading separators will not be
scanned off.
DS:SI = segment:offset of string
ES:DI = segment:offset of file control block
Returns:
AL = 00H if no wildcard characters encountered
01H if parsed string contained wildcard characters
FFH if drive specifier invalid
DS:SI = segment:offset of first character after parsed filename
ES:DI = segment:offset of formatted unopened file control block
Notes:
This function regards the following as separator characters:
[1] : . ; , = + tab space / " [ ]
[2.0+] : . ; , = + tab space
This function regards all control characters and the following as terminator characters:
: . ; , = + tab space < > | / " [ ]
If no valid filename is present in the string to be parsed, upon return ES:DI + 1 points to an ASCII blank.
If the * wildcard character occurs in a filename or extension, it and all remaining characters in the corresponding field in the FCB are set to ?.
This function (and file control blocks in general) cannot be used with file specifications that include a path.
Example:
Parse the string fname into the file control block myfcb.
fname db 'D:QUACK.DAT',0 ; filename to be parsed
myfcb db 37 dup (0) ; becomes file control block
.
.
.
mov ah,29h ; function number
mov al,01h ; skip leading separators
mov si,seg fname ; address of filename
mov ds,si
mov si,offset fname
mov di,seg myfcb ; address of FCB
mov es,di
mov di,offset myfcb
int 21h ; transfer to MS-DOS
cmp al,0ffh ; check status
je error ; jump, drive invalid
.
.
.