From 7b1cb65eefcd2ce1a734d33356a7c0683fa96dde Mon Sep 17 00:00:00 2001
From: Ivan Izaguirre <ivanizag@gmail.com>
Date: Wed, 30 Jan 2019 20:10:39 +0100
Subject: [PATCH] Support for STA, STX, STY

---
 execute.go      | 28 ++++++++++++++++++++++++----
 execute_test.go | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/execute.go b/execute.go
index de56ede..fce6e89 100644
--- a/execute.go
+++ b/execute.go
@@ -152,6 +152,14 @@ func buildOpLoad(addressMode int, regDst int) opFunc {
 	}
 }
 
+func buildOpStore(addressMode int, regSrc int) opFunc {
+	return func(s *state, line []uint8, opcode opcode) {
+		_, setValue := resolveWithAddressMode(s, line, addressMode)
+		value := s.registers.getRegister(regSrc)
+		setValue(value)
+	}
+}
+
 func buildOpUpdateFlag(flag uint8, value bool) opFunc {
 	return func(s *state, line []uint8, opcode opcode) {
 		s.registers.updateFlag(flag, value)
@@ -199,10 +207,6 @@ PHP
 PLA
 PLP
 
-STA
-STX
-STY
-
 */
 
 var opcodes = [256]opcode{
@@ -270,6 +274,22 @@ var opcodes = [256]opcode{
 	0xAC: opcode{"LDY", 3, 4, buildOpLoad(modeAbsolute, regY)},
 	0xBC: opcode{"LDY", 3, 4, buildOpLoad(modeAbsoluteX, regY)}, // Extra cycles
 
+	0x85: opcode{"STA", 2, 3, buildOpStore(modeZeroPage, regA)},
+	0x95: opcode{"STA", 2, 4, buildOpStore(modeZeroPageX, regA)},
+	0x8D: opcode{"STA", 3, 4, buildOpStore(modeAbsolute, regA)},
+	0x9D: opcode{"STA", 3, 5, buildOpStore(modeAbsoluteX, regA)},
+	0x99: opcode{"STA", 3, 5, buildOpStore(modeAbsoluteY, regA)},
+	0x81: opcode{"STA", 2, 6, buildOpStore(modeIndexedIndirectX, regA)},
+	0x91: opcode{"STA", 2, 6, buildOpStore(modeIndirectIndexedY, regA)},
+
+	0x86: opcode{"STX", 2, 3, buildOpStore(modeZeroPage, regX)},
+	0x96: opcode{"STX", 2, 4, buildOpStore(modeZeroPageY, regX)},
+	0x8E: opcode{"STX", 3, 4, buildOpStore(modeAbsolute, regX)},
+
+	0x84: opcode{"STY", 2, 3, buildOpStore(modeZeroPage, regY)},
+	0x94: opcode{"STY", 2, 4, buildOpStore(modeZeroPageX, regY)},
+	0x8C: opcode{"STY", 3, 4, buildOpStore(modeAbsolute, regY)},
+
 	0x90: opcode{"BCC", 2, 2, buildOpBranch(flagC, false)}, // Extra cycles
 	0xB0: opcode{"BCS", 2, 2, buildOpBranch(flagC, true)},  // Extra cycles
 	0xD0: opcode{"BNE", 2, 2, buildOpBranch(flagZ, false)}, // Extra cycles
diff --git a/execute_test.go b/execute_test.go
index ac44d95..7134d67 100644
--- a/execute_test.go
+++ b/execute_test.go
@@ -86,6 +86,38 @@ func TestLoad(t *testing.T) {
 	}
 }
 
+func TestStore(t *testing.T) {
+	var s state
+	s.registers.setA(0x10)
+	s.registers.setX(0x40)
+	s.registers.setY(0x80)
+
+	executeLine(&s, []uint8{0x85, 0x50})
+	if s.memory[0x0050] != 0x10 {
+		t.Error("Error in STA zpg")
+	}
+
+	executeLine(&s, []uint8{0x86, 0x51})
+	if s.memory[0x0051] != 0x40 {
+		t.Error("Error in STX zpg")
+	}
+
+	executeLine(&s, []uint8{0x84, 0x52})
+	if s.memory[0x0052] != 0x80 {
+		t.Error("Error in STY zpg")
+	}
+
+	executeLine(&s, []uint8{0x8D, 0x20, 0xC0})
+	if s.memory[0xC020] != 0x10 {
+		t.Error("Error in STA abs")
+	}
+
+	executeLine(&s, []uint8{0x9D, 0x08, 0x10})
+	if s.memory[0x1048] != 0x10 {
+		t.Error("Error in STA abs, X")
+	}
+}
+
 func TestTransfer(t *testing.T) {
 	var s state