zasm: code consolidation

apps/zasm/instr.asm

@@ -57,7 +57,6 @@ I_SBC	.equ	0x2f
 I_SCF	.equ	0x30
 I_SUB	.equ	0x31
 I_XOR	.equ	0x32
-I_BAD	.equ	0xff
 
 ; Checks whether A is 'N' or 'M'
 checkNOrM:
@@ -77,27 +76,15 @@ checknmxy:
 	cp	'y'
 	ret
 
-; Reads instruction mnemonic in (HL) and returns the corresponding ID (I_*)
-; in A. I_BAD if there's no match.
+; Reads string in (HL) and returns the corresponding ID (I_*) in A. Sets Z if
+; there's a match.
 getInstID:
 	push	bc
 	push	de
 	ld	b, I_XOR+1	; I_XOR is the last
+	ld	c, 4
 	ld	de, instrNames
-.loop:
-	ld	a, 4
-	call	JUMP_STRNCMP
-	ld	a, 4
-	call	JUMP_ADDDE
-	jr	z, .match
-	djnz	.loop
-	; no match
-	ld	a, I_BAD
-	jr	.end
-.match:
-	ld	a, I_XOR+1
-	sub	b
-.end:
+	call	findStringInList
 	pop	de
 	pop	bc
 	ret
@@ -788,7 +775,7 @@ parseTokens:
 	push	hl
 	push	de
 	ld	a, (tokInstr)
-	cp	I_BAD
+	cp	TOK_BAD
 	jr	z, .error	; for now, we treat blank lines as errors
 	ld	hl, tokArg1
 	ld	de, curArg1

apps/zasm/tok.asm

@@ -5,6 +5,10 @@
 ; *** Requirements ***
 ; JUMP_UPCASE
 
+; *** Consts ***
+TOK_INSTR	.equ	0x01
+TOK_BAD		.equ	0xff
+
 ; *** Code ***
 ; Parse line in (HL) and read the next token in (DE). For now, it only supports
 ; instructions. Arguments must be tokenized with the appropriate specialized
@@ -19,6 +23,10 @@ tokenize:
 	ex	hl, de
 	call	getInstID
 	ex	hl, de
+	jr	z, .match
+	; no match
+	ld	a, TOK_BAD
+.match:
 	ld	(de), a
 	ret
 

apps/zasm/util.asm

@@ -65,4 +65,30 @@ enterParens:
 	call	JUMP_UNSETZ
 	ret
 
-
+; Find string (HL) in string list (DE) of size B. Each string is C bytes wide.
+; Returns the index of the found string. Sets Z if found, unsets Z if not found.
+findStringInList:
+	push	de
+	push	bc
+.loop:
+	ld	a, c
+	call	JUMP_STRNCMP
+	ld	a, c
+	call	JUMP_ADDDE
+	jr	z, .match
+	djnz	.loop
+	; no match, Z is unset
+	pop	bc
+	pop	de
+	ret
+.match:
+	; Now, we want the index of our string, which is equal to our initial B
+	; minus our current B. To get this, we have to play with our registers
+	; and stack a bit.
+	ld	d, b
+	pop	bc
+	ld	a, b
+	sub	d
+	pop	de
+	cp	a		; ensure Z
+	ret