From be6555052532fc201d9e1ea38bc3237693e21f65 Mon Sep 17 00:00:00 2001
From: Alex Weisberger <alex.m.weisberger@gmail.com>
Date: Wed, 1 Oct 2014 18:02:45 -0400
Subject: [PATCH] fetch, decode, execute loop

---
 src/bin/main.rs | 13 ++++++++-----
 src/machine.rs  | 24 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/src/bin/main.rs b/src/bin/main.rs
index 6154dee..c264f8f 100644
--- a/src/bin/main.rs
+++ b/src/bin/main.rs
@@ -31,10 +31,13 @@ use emu6502::machine;
 
 fn main() {
     let mut machine = machine::Machine::new();
-    
-    println!("A: {}", machine.registers.accumulator);
-    println!("add_with_carry(1)");
-    machine.add_with_carry(1);
-    println!("A: {}", machine.registers.accumulator);
+
+    for _ in range(0u, 2u) {
+        let raw_instruction = machine.fetch_instruction();
+        let instruction = machine.decode_instruction(raw_instruction);
+        machine.execute_instruction(instruction);
+    }
+
+    println!("Ran program, output of Accum is {}", machine.registers.accumulator);
 }
 
diff --git a/src/machine.rs b/src/machine.rs
index 5ae4086..1893ccb 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -25,6 +25,10 @@
 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 // POSSIBILITY OF SUCH DAMAGE.
 
+use address::Address;
+use address::AddressDiff;
+use instruction::Instruction;
+use instruction::ADC;
 use memory::Memory;
 use registers::{ Registers, Status, StatusArgs };
 use registers::{ ps_negative, ps_overflow, ps_zero, ps_carry };
@@ -45,6 +49,26 @@ impl Machine {
     pub fn reset(&mut self) {
     	*self = Machine::new();
     }
+
+    pub fn fetch_instruction(&mut self) -> u8  {
+        let instr = self.memory.get_byte(&self.registers.program_counter);
+        self.registers.program_counter.add(&AddressDiff(1));
+        instr                    
+    }
+
+    pub fn decode_instruction(&mut self, raw_instruction: u8) -> Instruction {
+        ADC
+    }    
+        
+    pub fn execute_instruction(&mut self, instruction: Instruction) {
+        match instruction {
+            ADC => { 
+                println!("executing add with carry");
+                self.add_with_carry(1);
+            }
+            _ => println!("attempting to execute unimplemented instruction")
+        };
+    }
     
     // TODO akeeton: Implement binary-coded decimal.
     pub fn add_with_carry(&mut self, value: i8) {