Implement file search in directory

boot/kernel.asm

@@ -35,13 +35,9 @@ relinit:	; print banner
 		push word [version+2]
 		call printf
 		db "RDOS ",2,2, 0x0A, 0x0D, 0
-
-		push dx
-		push ds
+		; initialize the disk i/o
 		call dinit
-		pop ds
-		pop dx
-
+		; init 21h vector
 		mov word [0x21*4], int21
 		mov word [0x21*4+2], cs
 		; set current PSP, directly after us
@@ -49,15 +45,19 @@ relinit:	; print banner
 		mov cl, 4
 		shr ax, cl
 		mov word [curpsp], ax
+		; also the DTA
+		mov bx, dta
+		call setdta
+		; set current drive to boot drive
+		mov al, dl
+		rol al, 1
+		rol al, 1
+		or dl, al
+		and dl, 3
+		call setdd
 
-		cmp dl, 0x80
-		jc .k
-		sub dl, (0x80-2)
-.k:		call setdd
-
-		mov dx, testfcb
-		mov ah, 0xF
-		int 0x21
+		mov bx, testfcb
+		call fndfst
 
 restart:
 hlt:		hlt
@@ -70,6 +70,10 @@ hlt:		hlt
 %include	"kernel/drive.asm"
 %include	"kernel/printf.asm"
 
+section .bss
+
+dta:		resb 128
+
 section .data
 
 testfcb:	db 0

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

@@ -10,14 +10,18 @@ FCBSIZ:	equ 30
 section .text
 
 	; auto-complete drive field in fcb
+	; also returns the drive number
 	; IN	es:bx	far ptr FCB
-		; OUT	si	copy of bx
-fixfcb:		cmp byte [es:bx], 0
-		jne .ret
+	; 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 byte [es:bx], dl
-.ret:		ret
+	mov [es:bx], dl
+.ret:	dec dl
+	ret
 
 	; Load root directory entry
 	; IN	ax	number of directory entry
@@ -37,8 +41,55 @@ lddir:		push ax
 
 	; find first matching file
 	; IN	ES:BX	input fcb
-fndfst:		
-
+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