# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1392625037 -7200
# Node ID e56d8b0eee4b17ac62941b52e6e199791f7b1d50

spectrum fractal :)

diff -r 000000000000 -r e56d8b0eee4b Makefile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Makefile	Mon Feb 17 10:17:17 2014 +0200
@@ -0,0 +1,16 @@
+src = test.c
+obj = $(src:.c=.o)
+
+bin = test.tap
+
+CC = zcc
+CFLAGS = +zx -pragma-define=myzorg=28000
+LDFLAGS = -create-app
+
+$(bin): $(obj)
+	rm -f $(bin)
+	$(CC) $(CFLAGS) -o $@ $(LDFLAGS) $(obj)
+
+.PHONY: clean
+clean:
+	rm -f $(obj) $(bin)
diff -r 000000000000 -r e56d8b0eee4b RUN
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/RUN	Mon Feb 17 10:17:17 2014 +0200
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+fuse-sdl -g 3x --tape $*
diff -r 000000000000 -r e56d8b0eee4b test.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test.c	Mon Feb 17 10:17:17 2014 +0200
@@ -0,0 +1,69 @@
+#define FB_ADDR		((unsigned char*)0x4000)
+#define ATTR_ADDR	((unsigned char*)0x5800)
+#define LINESKIP	(256 / 8)
+
+unsigned char mbrot(int px, int py);
+
+int main()
+{
+	unsigned int i, j, k, start;
+
+	for(;;) {
+		start = 0;
+
+		for(i=0; i<192; i++) {
+			unsigned int banky = i & 0x3f;
+			unsigned int cell = banky / 8;
+			unsigned int cline = banky % 8;
+			unsigned int memline = cell + cline * 8;
+			unsigned char *ptr = FB_ADDR + (start + memline) * LINESKIP;
+
+			for(j=0; j<32; j++) {	/* 256 pixels, 8 pixels per byte */
+				unsigned char pixel = 0;
+				for(k=0; k<8; k++) {
+					unsigned char res = mbrot((j << 3) + k, i);
+					pixel = pixel | (res & 1);
+					if(k < 7) pixel <<= 1;
+				}
+				*ptr++ = pixel;
+			}
+
+			if((i & 0x3f) == 0x3f) {
+				start += 0x40;
+			}
+		}
+	}
+}
+
+#define int2fix8_8(i)		((i) << 8)
+#define fix_mul8_8(a, b)	((a >> 4) * (b >> 4))
+#define int2fix5_11(i)		((i) << 11)
+#define fix_mul5_11(a, b)	((a >> 5) * (b >> 6))
+
+unsigned char mbrot(int px, int py)
+{
+	unsigned char i;
+	int cx, cy, zx, zy, x, y, len;
+
+	cx = int2fix8_8(px - 192) >> 6;
+	cy = int2fix8_8(py - 96) >> 6;
+
+	cx <<= 3;
+	cy <<= 3;
+
+	zx = cx;
+	zy = cy;
+
+	for(i=0; i<32; i++) {
+		x = fix_mul5_11(zx, zx) - fix_mul5_11(zy, zy) + cx;
+		y = fix_mul5_11(zy, zx) + fix_mul5_11(zx, zy) + cy;
+		len = fix_mul5_11(x, x) + fix_mul5_11(y, y);
+
+		if(len > int2fix5_11(4)) return 0;
+
+		zx = x;
+		zy = y;
+	}
+
+	return 1;
+}