From 64b6fca5f33b619e9c38778000f5192521a57cf6 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Sun, 14 Nov 2021 13:55:21 +0000
Subject: [PATCH] fizzbuzz.s: Abstract out a number of system dependencies.

Maybe you can see where this is going.
---
 Makefile   |  2 +-
 fizzbuzz.s | 52 ++++++++++++++++++----------------------------------
 spectrum.s | 29 +++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 35 deletions(-)
 create mode 100644 spectrum.s

diff --git a/Makefile b/Makefile
index 9bef433..0af35b7 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,7 @@ TARGETS			 =
 CLEANFILES		 = $(TARGETS)
 
 CLEANFILES		+= spectrum-fb.img
-spectrum-fb.img: fizzbuzz.s
+spectrum-fb.img: spectrum.s fizzbuzz.s
 	z80asm -o $@ $^
 
 TARGETS			+= spectrum-fizzbuzz.tap
diff --git a/fizzbuzz.s b/fizzbuzz.s
index 58d4928..8521554 100644
--- a/fizzbuzz.s
+++ b/fizzbuzz.s
@@ -2,21 +2,6 @@
 ;;;
 ;;; Best not to ask why.
 
-	org	0xf000
-
-print_a: equ	0x10
-tvflag:	equ	0x5c3c
-
-entry:
-	;; Initialize the buffer.
-	ld	a, 1
-	ld	(buf), a
-	ld	(len), a
-
-	;; Use the main screen.
-	xor	a
-	ld	(tvflag), a
-
 	;; Look at the buffer and decide what to do.
 again:	ld	e, 0
 
@@ -42,7 +27,7 @@ mod3_1:	djnz	mod3
 	call	squish
 	call	squish
 
-	cp	0
+	and	a
 	jr	z, prfizz
 	cp	3
 	jr	z, prfizz
@@ -68,7 +53,7 @@ prbuzz:	ld	hl, buzz
 
 	;; Not a multiple of five.  Skip ahead if it was a multiple of three.
 nobuzz:	ld	a, e
-	cp	0
+	and	a
 	jr	nz, prnl
 
 	;; OK, so just print the value.
@@ -86,12 +71,12 @@ nobuzz:	ld	a, e
 	srl	a
 	srl	a
 	jr	z, skiplz
-	or	0x30
-	rst	print_a
+	fixdig
+	print_a
 skiplz:	ld	a, d
 	and	0x0f
-	or	0x30
-	rst	print_a
+	fixdig
+	print_a
 	dec	b
 	jr	z, prnl
 
@@ -102,17 +87,17 @@ prdig:	dec	hl
 	srl	a
 	srl	a
 	srl	a
-	or	0x30
-	rst	print_a
+	fixdig
+	print_a
 	ld	a, d
 	and	0x0f
-	or	0x30
-	rst	print_a
+	fixdig
+	print_a
 	djnz	prdig
 
 	;; Print the newline.
-prnl:	ld	a, ' '
-	rst	print_a
+prnl:	ld	a, spc
+	print_a
 
 	;; Increment the counter.
 	ld	hl, buf
@@ -153,14 +138,13 @@ squish:
 print:
 	;; Print the string at hl.
 	ld	a, (hl)
-	cp	0
+	endstrp
 	ret	z
-	rst	print_a
+	print_a
 	inc	hl
 	jr	print
 
-fizz:	defb	"fizz", 0
-buzz:	defb	"buzz", 0
-
-len:	defb	0
-buf:	defs	256
+	;; Initial state.  The buffer notionally continues for another 254
+	;; bytes, but there's no point in including them in the image.
+len:	db	1
+buf:	db	1
diff --git a/spectrum.s b/spectrum.s
new file mode 100644
index 0000000..01c29f8
--- /dev/null
+++ b/spectrum.s
@@ -0,0 +1,29 @@
+;;; -*-asm-*-
+
+	org	0x7000
+
+spc:	equ	' '
+
+tvflag:	equ	0x5c3c
+
+fixdig:	macro
+	or	0x30
+	endm
+
+print_a: macro
+	rst	0x10
+	endm
+
+endstrp: macro
+	and	a
+	endm
+
+	jr	setup
+
+fizz:	db	"fizz", 0
+buzz:	db	"buzz", 0
+
+setup:
+	;; Use the main screen.
+	xor	a
+	ld	(tvflag), a
-- 
2.11.0