Implement file search in directory

kernel/drive.asm

@@ -34,6 +34,7 @@ section .text
 
 		; initial setup for disk i/o
 dinit:		; copy previously set DPT to our data area
+		push ds
 		push cs
 		pop es
 		lds si, [es:4*0x1E]
@@ -45,6 +46,7 @@ dinit:		; copy previously set DPT to our data area
 		mov word [cs:4*0x1E+2], ds
 		; set to invalid drive
 		mov byte [cs:dsknum], 0xFF
+		pop ds
 		ret
 
 		; int 13 stub

kernel/fcb.asm

@@ -9,36 +9,87 @@ FCBSIZ:	equ 30
 
 section .text
 
-		; auto-complete drive field in fcb
-		; IN	es:bx	far ptr FCB
-		; OUT	si	copy of bx
-fixfcb:		cmp byte [es:bx], 0
-		jne .ret
-		call getdd
-		inc dl
-		mov byte [es:bx], dl
-.ret:		ret
+	; 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:		
+	; 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
+	ret