rdos/kernel/fcb.asm

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; FCB layout
; 1 byte drive (0=default, 1=A:, 2=B:, ...)
; 8.3 filename
; 8.3 filename for rename
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FCBDEN: equ 23 ; WORD directory entry number
FCBSIZ: equ 30
section .text
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; auto-complete drive field in fcb
; also returns the drive number
; IN es:bx far ptr FCB
; OUT dl dl (0=A:, 1=B:, 2=C:, ...)
fcbdrv: mov dl, [es:bx]
test dl, dl
jnz .ret
call getdd
mov dl, al
inc dl
mov [es:bx], dl
.ret: dec dl
ret
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; Load root directory entry
; IN ax number of directory entry
; OUT cs:si ptr to directory entry
lddir: push ax
mov cl, 4
shr ax, cl
xor dx, dx
call maprd
; get si to point to entry
pop si
mov cl, 5
shl si, cl
and si, 0x1FF
add si, dskbuf
ret
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; find first matching file
; IN ES:BX input fcb
fndfst: ; get and log in drive
call fcbdrv
call logdrv
; set search state to zero
push es
push bx
call getdta
xor ax, ax
mov [es:bx+0x20+1], ax
pop bx
pop es
; find next matching file
; state is kept in DTA
fndnxt: ; get net direntry to fetch
; get number of current entry from DTA
push es
push bx
call getdta
mov ax, [es:bx+0x20+1]
inc word [es:bx+0x20+1]
pop bx
pop es
; bail out if we are at end of dir
cmp ax, [bpb+BPBRDE]
jnc .err
; load entry and first byte
push bx
call lddir
pop bx
; next if hidden, dir or vol label
test byte [si+0x0B], 0xDA
jnz fndnxt
; bail out if end of dir
mov al, [si]
cmp al, 0
je .err
; next if deleted entry
cmp al, 0xE5
je fndnxt
; compate DS:SI with ES:BX+1
lea di, [bx+1]
mov cx, 11
rep cmpsb
; try next if mismatch
jne fndnxt
clc
ret
.err: stc
ret
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open:
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ret