Use optimized error handling for boot sector

boot/fat32.asm

@@ -28,23 +28,7 @@ init:	xor ax, ax
 	rep movsw
 	jmp 0x0:main
 
-msg:	pop si
+	%include "inc/booterr.asm"
-mloop:	lodsb
-	test al, al
-	jz mend
-	mov ah, 0x0e
-	mov bx, 7
-	int 0x10
-	jmp mloop
-mend:	push si
-	ret
-
-dskerr: call msg
-	db "DISK", 0
-err:	call msg
-	db "ERR", 0x0A, 0x0D, 0
-hlt:	hlt
-	jmp hlt
 
 	; offsets relative to FS
 readd:	; add offset of cluster data area to DX:AX
@@ -69,7 +53,7 @@ readf:	; add offset to FAT table to DX:AX
 readp:	; read sector DX:AX from partition
 	add ax, word [bp+bpb_po]
 	adc dx, word [bp+bpb_po+2]
-	jc err
+	jc dskerr
 read_:	; read sector DX:AX from disk
 	; qword sector number DX:AX
 	push cs
@@ -99,6 +83,9 @@ read_:	; read sector DX:AX from disk
 
 	ret
 
+	; error handling for disk errors
+dskerr: call errcll
+
 next:	; Advances DX:AX to next FAT entry
 	push ax
 	push bx
@@ -181,7 +168,7 @@ loop:	add si, 0x20
 	mov al, [si]
 	; unallocated direntry
 	test al, al
-	jz end
+	jz fserr
 	; deleted files
 	cmp al, 0xE2
 	je loop
@@ -197,7 +184,7 @@ loadr:	mov ax, 2
 	jmp load
 
 loadf:	call search
-	jne end
+	jne fserr
 	mov ax, [si+0x1A]
 	mov dx, [si+0x14]
 	jmp load
@@ -228,9 +215,8 @@ main:	mov bp, bpb
 
 	jmp 0:0x7C00
 
-end:	call msg
+	; error handling for file not found
-	db "DIR", 0
+fserr:	call errcll
-	jmp err
 
 	; Padding and signature
 	times (0x1FE - ($-$$)) db 0

inc/booterr.asm

@@ -0,0 +1,18 @@
+errcll:	pop dx
+errjmp:	call dmpdx
+hlt:	hlt
+	jmp hlt
+dmpdx:	xor bx, bx
+	mov ah, 0x0e
+	mov cl, 4
+	call dmpdx1
+dmpdx1:	call dmpdx2
+dmpdx2:	mov al, dh
+	shl dx, cl
+	shr al, cl
+	add al, 0x30
+	cmp al, 0x3a
+	jl dmpdx3
+	add al, 7
+dmpdx3:	int 0x10
+	ret