From e2da2bffe58a76c091d3496bd3ca2d2f18ea2eb6 Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Thu, 13 Nov 2025 05:39:38 -0500
Subject: initial commit

---
 f65/f65.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 f65/f65.c

(limited to 'f65/f65.c')

diff --git a/f65/f65.c b/f65/f65.c
new file mode 100644
index 0000000..952eac3
--- /dev/null
+++ b/f65/f65.c
@@ -0,0 +1,68 @@
+/* fake 6502. a perl script converts this:
+
+	ldy #10
+loop:
+	lda blah,y
+	sta (p1),y
+	dey
+	bpl loop
+
+to something like:
+	ldy_i(10)
+loop:
+	lda_absy(blah)
+	sta_zpy(p1)
+	dey();
+	bpl(loop);
+
+where e.g.
+
+	#define ldy_i(x) Y=x; ZF=!Y; NF=Y&0x80;
+
+	#define lda_absy(x) A=mem[x+y]; ZF=!A; NF=A&0x80;
+
+	#define sta_zpy(x) mem[(mem[x] | mem[x+1] << 8) + y] = A;
+
+	#define dey() Y--; ZF=!Y; NF=Y&0x80;
+
+	#define bpl(x) if(!NF) goto x
+
+...and the 'loop:' is a real C line label.
+
+we don't worry about the V flag since unalf doesn't use it.
+
+This isn't emulation exactly, and it isn't dynamic recompilation because
+it's static. "Static recompilation" maybe?
+
+*/
+
+#include "f65.h"
+
+u8 A, X, Y, S = 0xff, tmp; /* tmp is result for cmp/cpx/cpy */
+u8 mem[1 << 16]; /* 64K */
+u8 *stack = mem + 0x100; /* page 1 */
+
+u8 CF, ZF, NF; /* flags should really be a bitfield, *shrug* */
+
+unsigned int wtmp;
+
+void dump_state(void) {
+	fprintf(stderr,
+			"A = $%02x  X = $%02x  Y = $%02x  S = $%02x | "
+			"CF = %d  ZF=%d  NF=%d\n",
+			A, X, Y, S, (CF ? 1 : 0), (ZF ? 1 : 0), (NF ? 1 : 0));
+}
+
+void dump_mem(int start, int end) {
+	int count = 0;
+	while(start <= end) {
+		if(count % 16 == 0) {
+			if(count) fputc('\n', stderr);
+			fprintf(stderr, "%04x:", start);
+		}
+		fprintf(stderr, " %02x", mem[start]);
+		count++;
+		start++;
+	}
+	fputc('\n', stderr);
+}
-- 
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