From 448c7022378ab87b12652d608429c77d107229c5 Mon Sep 17 00:00:00 2001
From: Stephen Crane <jscrane@gmail.com>
Date: Sun, 24 Feb 2019 12:41:33 +0000
Subject: [PATCH] replace BCD maps with functions

---
 r6502.cpp | 21 ++++++++++++---------
 r6502.h   |  1 -
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/r6502.cpp b/r6502.cpp
index b7b004f..3e1a999 100644
--- a/r6502.cpp
+++ b/r6502.cpp
@@ -148,12 +148,20 @@ void r6502::jsr() {
 	PC = vector(PC);
 }
 
+static inline uint8_t fromBCD(uint8_t i) {
+	return ((i >> 4) & 0x0f)*10 + (i & 0x0f);
+}
+
+static inline uint8_t toBCD(uint8_t i) {
+	return (((i % 100) / 10) << 4) | (i % 10);
+}
+
 void r6502::_adc(uint8_t d) {
 	if (P.bits.D) {
-		int r = _fromBCD[A] + _fromBCD[d] + C;
+		int r = fromBCD(A) + fromBCD(d) + C;
 		C = (r > 99);
 		if (C) r -= 100;
-		A = _toBCD[r];
+		A = toBCD(r);
 	} else {
 		unsigned short u = (unsigned short)A + (unsigned short)d + (unsigned short)C;
 		short s = (char)A + (char)d + (char)C;
@@ -166,10 +174,10 @@ void r6502::_adc(uint8_t d) {
 }
 
 void r6502::sbcd(uint8_t d) {
-	int r = _fromBCD[A] - _fromBCD[d] - !C;
+	int r = fromBCD(A) - fromBCD(d) - !C;
 	C = (r >= 0);
 	if (r < 0) r += 100;
-	A = _toBCD[r & 0xff];
+	A = toBCD(r & 0xff);
 	N = (A & 0x80);
 	Z = A;
 	// V not tested for: http://www.6502.org/tutorials/decimal_mode.html
@@ -193,11 +201,6 @@ void r6502::reset()
 
 r6502::r6502(Memory &m): CPU(m) {
 
-	for (int i=0; i < 256; i++) {
-		_fromBCD[i] = ((i >> 4) & 0x0f)*10 + (i & 0x0f);
-		_toBCD[i] = (((i % 100) / 10) << 4) | (i % 10);
-	}
-
 	OP *p = _ops;
 	*p++=&r6502::brk; *p++=&r6502::ora_ix; *p++=&r6502::ill; *p++=&r6502::ill;
 	*p++=&r6502::nop2; *p++=&r6502::ora_z; *p++=&r6502::asl_z; *p++=&r6502::ill;
diff --git a/r6502.h b/r6502.h
index 7bd9891..e034112 100644
--- a/r6502.h
+++ b/r6502.h
@@ -33,7 +33,6 @@ private:
 		} bits;
 		uint8_t flags;
 	} P;
-	uint8_t _toBCD[256], _fromBCD[256];	// BCD maps
 	bool _irq;				// interrupt pending?
 
 	void irq();