From 9b0dac5ac8662767446567b90abc65f8f8657f37 Mon Sep 17 00:00:00 2001
From: Ivan Izaguirre <ivanizag@gmail.com>
Date: Mon, 28 Jan 2019 23:10:23 +0100
Subject: [PATCH] Fixed ROL A, added ROR

---
 execute.go      | 36 ++++++++++++++++++++++++++----------
 execute_test.go | 27 +++++++++++++++++++++++++--
 registers.go    | 12 +++++++++---
 3 files changed, 60 insertions(+), 15 deletions(-)

diff --git a/execute.go b/execute.go
index 2074277..fe2e303 100644
--- a/execute.go
+++ b/execute.go
@@ -68,6 +68,7 @@ func resolveWithAddressMode(s *state, line []uint8, addressMode int) (value uint
 	switch addressMode {
 	case modeAccumulator:
 		value = s.registers.getA()
+		hasAddress = false
 	case modeImmediate:
 		value = line[1]
 		hasAddress = false
@@ -97,16 +98,24 @@ func resolveWithAddressMode(s *state, line []uint8, addressMode int) (value uint
 	return
 }
 
-func buildRotateLeft(addressMode int) opFunc {
+func buildRotate(addressMode int, isLeft bool) opFunc {
 	return func(s *state, line []uint8, opcode opcode) {
 		value, hasAddress, address := resolveWithAddressMode(s, line, addressMode)
 
-		carry := value >= (7<<1)
-		value <<= 1
-		value += s.registers.getFlagBit(flagC)
+		oldCarry := s.registers.getFlagBit(flagC)
+		var carry bool
+		if isLeft {
+			carry = (value & 0x80) != 0
+			value <<= 1
+			value += oldCarry
+		} else {
+			carry = (value & 0x01) != 0
+			value >>= 1
+			value += oldCarry << 7
+		}
 		s.registers.updateFlag(flagC, carry)
 		s.registers.updateFlagZN(value)
-		
+
 		if hasAddress {
 			s.memory[address] = value
 		} else {
@@ -124,11 +133,18 @@ func buildOpLoad(addressMode int, regDst int) opFunc {
 }
 
 var opcodes = [256]opcode{
-	0x26: opcode{"ROL", 2, 5, buildRotateLeft(modeZeroPage)},
-	0x2A: opcode{"ROL", 1, 2, buildRotateLeft(modeAccumulator)},
-	0x2E: opcode{"ROL", 3, 6, buildRotateLeft(modeAbsolute)},
-	0x36: opcode{"ROL", 2, 6, buildRotateLeft(modeZeroPageX)},
-	0x3E: opcode{"ROL", 3, 7, buildRotateLeft(modeAbsoluteX)},
+	0x26: opcode{"ROL", 2, 5, buildRotate(modeZeroPage, true)},
+	0x2A: opcode{"ROL", 1, 2, buildRotate(modeAccumulator, true)},
+	0x2E: opcode{"ROL", 3, 6, buildRotate(modeAbsolute, true)},
+	0x36: opcode{"ROL", 2, 6, buildRotate(modeZeroPageX, true)},
+	0x3E: opcode{"ROL", 3, 7, buildRotate(modeAbsoluteX, true)},
+
+	0x66: opcode{"ROR", 2, 5, buildRotate(modeZeroPage, false)},
+	0x6A: opcode{"ROR", 1, 2, buildRotate(modeAccumulator, false)},
+	0x6E: opcode{"ROR", 3, 6, buildRotate(modeAbsolute, false)},
+	0x76: opcode{"ROR", 2, 6, buildRotate(modeZeroPageX, false)},
+	0x7E: opcode{"ROR", 3, 7, buildRotate(modeAbsoluteX, false)},
+
 	0x88: opcode{"DEY", 1, 2, buildOpIncDecRegister(regY, false)},
 	0x8A: opcode{"TXA", 1, 2, buildOpTransfer(regX, regA)},
 	0x98: opcode{"TYA", 1, 2, buildOpTransfer(regY, regA)},
diff --git a/execute_test.go b/execute_test.go
index 70ce222..1be46e4 100644
--- a/execute_test.go
+++ b/execute_test.go
@@ -128,13 +128,13 @@ func TestTransfer(t *testing.T) {
 	}
 }
 
-func TestIncDec(t * testing.T) {
+func TestIncDec(t *testing.T) {
 	var s state
 
 	s.registers.setX(0x7E)
 	executeLine(&s, []uint8{0xE8})
 	if s.registers.getX() != 0x7F {
-		t.Errorf("Error in INX %v", s.registers.getX())
+		t.Errorf("Error in INX")
 	}
 
 	s.registers.setY(0xFC)
@@ -145,5 +145,28 @@ func TestIncDec(t * testing.T) {
 	if s.registers.getP() != flagN {
 		t.Error("Error in DEY flags")
 	}
+}
+
+func TestRotate(t *testing.T) {
+	var s state
+
+	s.registers.setA(0xF0)
+	executeLine(&s, []uint8{0x2A})
+	if s.registers.getA() != 0xE0 {
+		t.Errorf("Error in ROL")
+	}
+	if !s.registers.getFlag(flagC) {
+		t.Errorf("Error in ROL carry. %v", s.registers)
+	}
+
+	s.registers.setFlag(flagC)
+	s.registers.setA(0x0F)
+	executeLine(&s, []uint8{0x6A})
+	if s.registers.getA() != 0x87 {
+		t.Errorf("Error in ROR. %v", s.registers)
+	}
+	if !s.registers.getFlag(flagC) {
+		t.Errorf("Error in ROR carry")
+	}
 
 }
diff --git a/registers.go b/registers.go
index 0018daa..a589176 100644
--- a/registers.go
+++ b/registers.go
@@ -1,5 +1,7 @@
 package main
 
+import "fmt"
+
 const (
 	regA  = 0
 	regX  = 1
@@ -52,13 +54,12 @@ func (r *registers) setPC(v uint16) {
 func (r *registers) getFlagBit(i uint8) uint8 {
 	if r.getFlag(i) {
 		return 1
-	} else {
-		return 0
 	}
+	return 0
 }
 
 func (r *registers) getFlag(i uint8) bool {
-	return (r.data[regP] & i ) != 0
+	return (r.data[regP] & i) != 0
 }
 
 func (r *registers) setFlag(i uint8) {
@@ -81,3 +82,8 @@ func (r *registers) updateFlagZN(t uint8) {
 	r.updateFlag(flagZ, t == 0)
 	r.updateFlag(flagN, t >= (1<<7))
 }
+
+func (r registers) String() string {
+	return fmt.Sprintf("A: %#02x, X: %#02x, Y: %#02x, SP: %#02x, PC: %#04x, P: %#02x, (NV-BDIZC): %08b",
+		r.getA(), r.getX(), r.getY(), r.getSP(), r.getPC(), r.getP(), r.getP())
+}