zasm: add support for string literals in .db

apps/zasm/directive.asm

@@ -30,13 +30,24 @@ handleDB:
 .loop:
 	call	readWord
 	ld	hl, scratchpad
+	call	enterDoubleQuotes
+	jr	z, .stringLiteral
 	call	parseLiteral
 	ld	a, ixl
 	call	ioPutC
+.stopStrLit:
 	call	readComma
 	jr	z, .loop
 	pop	hl
 	ret
+.stringLiteral:
+	ld	a, (hl)
+	inc	hl
+	or	a		; when we encounter 0, that was what used to
+	jr	z, .stopStrLit	; be our closing quote. Stop.
+	; Normal character, output
+	call	ioPutC
+	jr	.stringLiteral
 
 handleDW:
 	push	hl
@@ -96,23 +107,8 @@ handleINC:
 	call	readWord
 	jr	nz, .end
 	; HL points to scratchpad
-	; First, let's verify that our string is enquoted
-	ld	a, (hl)
-	cp	'"'
+	call	enterDoubleQuotes
 	jr	nz, .end
-	; We have opening quote
-	inc	hl
-	xor	a
-	call	findchar	; go to end of string
-	dec	hl
-	ld	a, (hl)
-	cp	'"'
-	jr	nz, .end
-	; we have ending quote, let's replace with null char
-	xor	a
-	ld	(hl), a
-	; Good, let's go back
-	ld	hl, scratchpad+1	; +1 because of the opening quote
 	call	ioOpenInclude
 .end:
 	xor	a		; zero bytes written

apps/zasm/util_z.asm

@@ -149,6 +149,39 @@ enterParens:
 	call	unsetZ
 	ret
 
+; Scans (HL) and sets Z according to whether the string is double quoted, that
+; is, starts with a " and ends with a ". If it is double quoted, "enter" them,
+; that is, advance HL by one and transform the ending quote into a null char.
+; If the string isn't double-enquoted, HL isn't changed.
+enterDoubleQuotes:
+	ld	a, (hl)
+	cp	'"'
+	ret	nz
+	push	hl
+	inc	hl
+	ld	a, (hl)
+	or	a		; already end of string?
+	jr	z, .nomatch
+	xor	a
+	call	findchar	; go to end of string
+	dec	hl
+	ld	a, (hl)
+	cp	'"'
+	jr	nz, .nomatch
+	; We have a match, replace ending quote with null char
+	xor	a
+	ld	(hl), a
+	; Good, let's go back
+	pop	hl
+	; ... but one char further
+	inc	hl
+	cp	a	; ensure Z
+	ret
+.nomatch:
+	call	unsetZ
+	pop	hl
+	ret
+
 ; Find string (HL) in string list (DE) of size B, in a case-insensitive manner.
 ; Each string is C bytes wide.
 ; Returns the index of the found string. Sets Z if found, unsets Z if not found.

tools/tests/zasm/test4.asm

@@ -6,3 +6,4 @@ ld	hl, 0x4234
 ld	hl, (0x4234)
 ld	a, 'X'
 ld	a, 'a'	; don't upcase!
+.db	"bonjour"