debug: Implement parsing of register names

debug/names.asm

@@ -0,0 +1,10 @@
+rnames:	; general purpose regs
+	db "AXCXDXBXSPBPSIDI"
+	; segment regs
+	db "ESCSSSDS"
+	; special regs
+	db "IPFL"
+fnames:	; control flags
+	db "++++ODIT"
+	; status flags
+	db "SZ+A+P+C"

debug/parse.asm

@@ -0,0 +1,58 @@
+	; IN	DS:SI	remaining unparsed string
+	;	CS:DI	error message
+parse_error:
+	push si
+	mov si, di
+	call putcs
+	mov al, ':'
+	call putc
+	mov al, ' '
+	call putc
+	pop si
+	call putds
+	jmp crlf
+
+eat_whitespace:
+	; peek on next char
+	mov al, [si]
+	; ES := CS
+	push es
+	push cs
+	pop es
+	; string search
+	mov di, .chars
+	mov cx, 4
+	scasb
+	; restore bss segment
+	pop es
+	jne .ret
+	inc si
+	jmp eat_whitespace
+.chars:	db 0x09, 0x0A, 0x0D, 0x20
+.ret:	ret
+
+	; IN:	DS:SI	string to read
+	; OUT:	CF set	if no match
+	;	BX	register number * 2 if CF clear
+eat_register:
+	push si
+	push es
+	lodsw
+	and ax, 0xDFDF
+	; ES := CS
+	push cs
+	pop es
+	mov di, rnames
+	mov cx, 14
+	repne scasw
+	pop es
+	jne .fail
+	pop bx
+	mov bx, di
+	sub bx, (rnames+2)
+	clc
+	ret
+.fail:	pop si
+	stc
+	ret
+.emsg:	db "Not a register name", 0