rdos/kernel/fcb.asm

; FCB layout
; 1 byte drive (0=default, 1=A:, 2=B:, ...)
; 8.3 filename
; 8.3 filename for rename

FCBDEN:	equ 23 ; WORD directory entry number
FCBSIZ:	equ 30

section .text

	; 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

	; 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

	; 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

open:
	ret