From 337f29a79b1d109df7bed3ebdc28f79654cae491 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sun, 1 Jul 2018 23:06:08 -0400
Subject: [PATCH] gr-sim: add shift and rotate support

---
 gr-sim/6502_emulate.c | 99 ++++++++++++++++++++++++++++++++++++++++++-
 gr-sim/6502_emulate.h |  5 +++
 2 files changed, 103 insertions(+), 1 deletion(-)

diff --git a/gr-sim/6502_emulate.c b/gr-sim/6502_emulate.c
index 565b31d2..616019cf 100644
--- a/gr-sim/6502_emulate.c
+++ b/gr-sim/6502_emulate.c
@@ -121,12 +121,109 @@ void lsr(void) {
 
 	temp_a=a;
 	temp_a&=0xff;
-	temp_a=temp_a>>1;
 
+	c=temp_a&0x1;
+	temp_a=temp_a>>1;
 	a=(temp_a&0xff);
+	z=(a==0);
+	n=!!(a&0x80);
 //	printf("LSR A=%x\n",a);
 }
 
+void asl(void) {
+	int temp_a;
+
+	temp_a=a;
+	temp_a&=0xff;
+
+	c=!!(temp_a&0x80);
+
+	temp_a=temp_a<<1;
+	a=(temp_a&0xff);
+	z=(a==0);
+	n=!!(a&0x80);
+//	printf("ASL A=%x\n",a);
+}
+
+
+void ror(void) {
+	int temp_a;
+	int old_c;
+
+	old_c=c;
+	temp_a=a;
+	temp_a&=0xff;
+
+	c=temp_a&0x1;
+	temp_a=temp_a>>1;
+	a=(temp_a&0xff);
+	a|=old_c<<7;
+
+	z=(a==0);
+	n=!!(a&0x80);
+//	printf("ROR A=%x\n",a);
+}
+
+void rol(void) {
+	int temp_a;
+	int old_c;
+
+	old_c=c;
+	temp_a=a;
+	temp_a&=0xff;
+
+	c=!!(temp_a&0x80);
+
+	temp_a=temp_a<<1;
+	a=(temp_a&0xff);
+	a|=old_c;
+
+	z=(a==0);
+	n=!!(a&0x80);
+//	printf("ROL A=%x\n",a);
+}
+
+
+
+void ror_mem(int addr) {
+	int temp_a;
+	int old_c;
+
+	old_c=c;
+	temp_a=ram[addr];
+	temp_a&=0xff;
+
+	c=temp_a&0x1;
+	temp_a=temp_a>>1;
+	ram[addr]=(temp_a&0xff);
+	ram[addr]|=old_c<<7;
+
+	z=(ram[addr]==0);
+	n=!!(ram[addr]&0x80);
+//	printf("ROR %x=%x\n",addr,ram[addr]);
+}
+
+void rol_mem(int addr) {
+	int temp_a;
+	int old_c;
+
+	old_c=c;
+	temp_a=ram[addr];
+	temp_a&=0xff;
+
+	c=!!(temp_a&0x80);
+
+	temp_a=temp_a<<1;
+	ram[addr]=(temp_a&0xff);
+	ram[addr]|=old_c;
+
+	z=(ram[addr]==0);
+	n=!!(ram[addr]&0x80);
+//	printf("ROL %x=%x\n",addr,ram[addr]);
+}
+
+
+
 unsigned char high(int value) {
 	return (value>>8)&0xff;
 }
diff --git a/gr-sim/6502_emulate.h b/gr-sim/6502_emulate.h
index fc67e629..cdf00854 100644
--- a/gr-sim/6502_emulate.h
+++ b/gr-sim/6502_emulate.h
@@ -12,6 +12,11 @@ void cmp(int value);
 void pha(void);
 void pla(void);
 void lsr(void);
+void asl(void);
+void ror(void);
+void rol(void);
+void ror_mem(int addr);
+void rol_mem(int addr);
 
 unsigned char high(int value);
 unsigned char low(int value);