Add skeleton of assembler

com/a86.asm

@@ -1,34 +1,25 @@
 	org 0x100
 
-		mov ax, 0x3D00
+	jmp init
-		mov dx, infile
-		int 0x21
-		jc err
 
-		mov [fd], ax
+fcb1	equ 0x5C
+eof	equ 0x1A
+stack	equ 0x10 ; stack size
 
-		call getline
+dumpax	push ax
-
+	push cx
-		mov dx, [line_length]
+	push dx
-		call dumpdx
+	mov dx, ax
-
+	call dmpdx0
-		mov si, line_buffer
+	mov al, 0x0A
-		mov cx, [line_length]
+	call dmpdx3
-		mov ah, 2
+	mov al, 0x0D
-l03:		lodsb
+	call dmpdx3
-		mov dl, al
+	pop dx
-		int 0x21
+	pop cx
-		loop l03
+	pop ax
-
+	ret
-end:		ret
+dmpdx0	mov ah, 0xe
-
-line_num:	dw 1
-
-err:		mov dx, ax
-
-dumpdx:		; setup bx and ah for int 10h call
-		xor bx, bx
-		mov ah, 0x0e
 	mov cl, 4
 	; this double-call is essentially a 4 times repeating loop
 	call dmpdx1
@@ -49,40 +40,228 @@ dmpdx2:		; grab highest nibble from dx
 dmpdx3:	int 0x10
 	ret
 
-		; read a character from the input file into DL
+free	dw 0 ; free ram size
-getc:		mov dl, 26
+lncnt	dw 0 ; line count
-		push dx
+rdptr	dw 0xFFFF ; infile blk ptr
-		mov ah, 0x3f
+symbol	dw 0 ; symbol of current line
-		mov bx, [fd]
+offset	dw 0 ; byte offset in outfile
-		mov cx, 1
+len	db 0 ; len for wrd (must be before it)
-		mov dx, sp
+wrd	dw 0,0,0,0,0,0,0,0 ; 16 byte word buf
+
+getc	mov bx, [rdptr]
+	cmp bx, 0x80
+	jc l01
+	mov ah, 0x14
+	mov dx, fcb1
 	int 0x21
-		pop dx
+	cmp al, 1
+	je l02
+	mov bx, 0
+l01	mov al, [0x80+bx]
+	cmp al, eof
+	je l02
+	cmp al, 0
+	je l02
+	cmp al, 0x0A
+	jne l01b
+	inc word [lncnt]
+l01b	inc bx
+	mov [rdptr], bx
+	jmp l03
+l02	mov al, 0x1A
+l03	cmp al, eof
 	ret
 
-getline:	mov word [line_length], 0
+;getc2	call peek
-		mov di, line_buffer
+;	cmp al, eof
-		mov cx, line_buflen
+;	jne getc_
-l02:		push cx
+;	inc word [rdptr]
-		call getc
+;getc_	ret
-		pop cx
-		mov al, dl
-		cmp al, 0x0A
-		je l01
-		cmp al, 0x0D
-		je l01
-		cmp al, 0x1A
-		je l01
-		inc word [line_length]
-		loop l02
 
-l01:		ret
+newlin	mov dl, 0x0A
+	mov ah, 2
+	int 0x21
+	mov dl, 0x0D
+	int 0x21
+	ret
 
-infile:		db "com/a86.asm", 0
+error	mov dl, [bx]
+	mov ah, 2
+	int 0x21
+	inc bx
+	cmp dl, 0x20
+	jne error
+	mov ax, [lncnt]
+	call dumpax
+	call newlin
+	int 0x20
 
-line_buflen:	equ 0x100
+e_eof	db "EOF "
-line_length:	dw 0 ; valid bytes in buffer
+e_dup	db "DUPSYM "
-line_prefix:	times 16 db " "
-line_buffer:	times line_buflen db 0
 
-fd:		dw 0
+	; scan word
+scawrd	mov si, wrd
+l04	call getc
+	; EOF is fatal
+	mov bx, e_eof
+	jz error
+	; tab=end
+	cmp al, 9
+	je pad
+	; space=end
+	cmp al, 0x20
+	je pad
+	; if lbl full, continue eating
+	cmp si, wrd+0x10
+	jnc l04
+	; insert
+	mov [si], al
+	inc si
+	jmp l04
+	; pad with spaces
+pad	mov cx, si
+	sub cx, wrd
+	mov [len], cl
+	cmp si, wrd+0x10
+	jnc l06
+	mov ah, 0x20
+	xchg ah, [si]
+	inc si
+	cmp ah, 0x20
+	jne pad
+l06	ret
+
+	; print wrd
+dmpwrd	mov si, wrd
+	mov cx, 0x10
+	mov ah, 2
+l05	mov dl, [si]
+	cmp dl, 0x20
+	je l07
+	inc si
+	int 0x21
+	loop l05
+l07	call newlin
+	ret
+
+	; create symbol table entry
+	; name is read from [wrd]
+	; offset is written to [symbol]
+symins	cmp byte [wrd], 0x20
+	je nosym
+	mov bx, init ; walk ptr
+	mov bp, [free]
+	add bp, bx ; end addr
+	jmp l09
+l08	add bx, 8
+l09	mov al, [bx]
+	cmp al, 0
+	je l10
+	call symcmp
+	jnz l08
+	mov bx, e_dup
+	jmp error
+	; copy str to table
+l10	mov si, wrd
+	mov di, bx
+	movsw
+	movsw
+	movsw
+	xor ax, ax
+	stosw
+	mov byte [bx+8], 0
+	mov [symbol], bx
+	ret
+
+nosym	xor ax, ax
+	mov [symbol], ax
+	ret
+
+	; compares 6 bytes [bx] with [wrd]
+	; bit 7 of each byte is ignored
+symcmp	mov si, wrd
+	xor ax, ax
+	mov dx, [wrd]
+	xor dx, [bx]
+	or ax, dx
+	mov dx, [wrd+2]
+	xor dx, [bx+2]
+	or ax, dx
+	mov dx, [wrd+4]
+	xor dx, [bx+4]
+	or ax, dx
+	test ax, 0x8F8F
+	ret
+
+	; look up keyword in wrd
+	; result is stored in bx
+lookup	mov ch, 0
+	mov bx, s_org
+l11	mov si, bx
+	mov di, len ; wrd immediately follows
+	mov cl, [bx]
+	test cx, cx
+	jz l13
+	inc cl
+	mov dx, cx
+	rep cmpsb
+	je l12
+	add bx, dx
+	jmp l11
+	; found!
+l12	clc
+	ret
+	; give up
+l13	xor bx, bx
+	stc
+	ret
+
+s_org	db 3, "org"
+s_equ	db 3, "equ"
+	db 0
+
+	; clear symbol table
+main	mov byte [init], 0
+	; scan and create label
+mloop	call scawrd
+	call symins
+	; scan instruction word
+	call scawrd
+	call lookup
+	; special stuff
+	cmp bx, s_org
+	je iorg
+	mov ax, bx
+	call dumpax
+	int 0x20
+
+	; org pseudo instruction
+iorg	mov ax, 0x5A5A
+	call dumpax
+	int 0x20
+
+	align 16
+
+	; stuff behind here gets overwritten
+	; by symbol table and program data
+
+init	mov ax, [6]
+	mov dx, sp
+	sub dx, stack
+	cmp ax, dx
+	jc il01
+	mov ax, dx
+il01	sub ax, init
+	shr ax, 1
+	and ax, 0xFFF0
+	mov [free], ax
+	; open input file
+	mov ah, 0x0F
+	mov dx, fcb1
+	int 0x21
+	mov bx, e_op
+	test al, al
+	jnz error
+	jmp main
+
+e_op	db "NOFILE "