From a5534ac375c171d86e0170ad777a11b8a6b8859d Mon Sep 17 00:00:00 2001
From: Johannes Muenzel <jmuenzel@gmail.com>
Date: Sat, 25 Oct 2014 19:04:52 -0400
Subject: [PATCH] Implement transfer instructions.

---
 src/machine.rs | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/machine.rs b/src/machine.rs
index d63d494..7229413 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -31,7 +31,7 @@ use address::{Address, AddressDiff};
 use instruction;
 use instruction::{DecodedInstr};
 use memory::Memory;
-use registers::{ Registers, Status, StatusArgs };
+use registers::{ Registers, StackPointer, Status, StatusArgs };
 use registers::{ PS_NEGATIVE, PS_OVERFLOW, PS_ZERO, PS_CARRY };
 
 pub struct Machine {
@@ -146,6 +146,35 @@ impl Machine {
                 self.memory.set_byte(addr, self.registers.index_y as u8);
             },
 
+            (instruction::TAX, instruction::UseImplied) => {
+                let val = self.registers.accumulator;
+                self.load_x_register(val);
+            },
+            (instruction::TAY, instruction::UseImplied) => {
+                let val = self.registers.accumulator;
+                self.load_y_register(val);
+            },
+            (instruction::TSX, instruction::UseImplied) => {
+                let StackPointer(val) = self.registers.stack_pointer;
+                let val = val as i8;
+                self.load_x_register(val);
+            },
+            (instruction::TXA, instruction::UseImplied) => {
+                let val = self.registers.index_x;
+                self.load_accumulator(val);
+            },
+            (instruction::TXS, instruction::UseImplied) => {
+                // Note that this is the only 'transfer' instruction that does
+                // NOT set the zero and negative flags. (Because the target
+                // is the stack pointer)
+                let val = self.registers.index_x;
+                self.registers.stack_pointer = StackPointer(val as u8);
+            },
+            (instruction::TYA, instruction::UseImplied) => {
+                let val = self.registers.index_y;
+                self.load_accumulator(val);
+            },
+
             (instruction::NOP, _) => {
                 debug!("nop instr");
             },