WIP: Split out opcode exec into function

This is not quite working yet!

src/main.rs

@@ -1,10 +1,45 @@
 use std::io::{self, Read};
 
+fn opcode(input: &Vec<u8>, counter: &usize) -> usize {
+    let size: usize;
+
+    let opcode = input[counter];
+
+    match opcode {
+        0x00 => { println!("NOP"); size = 1 },
+        0x21 => {
+            println!("LXI ${:x}{:x}", input[counter + 2], input[counter + 1]);
+            size = 3;
+        },
+        0x32 => {
+            println!("STA ${:x}{:x}", input[counter + 2], input[counter + 1]);
+            size = 3;
+        },
+        0x3e => {
+            println!("MVI A,#0x{:x}", input[counter + 1]);
+            size = 2;
+        },
+        0xc3 => {
+            println!("JMP ${:x}{:x}", input[counter + 2], input[counter + 1]);
+            size = 3;
+        },
+        0xc5 => { println!("PUSH B"); size = 1 },
+        0xd5 => { println!("PUSH D"); size = 1},
+        0xe5 => { println!("PUSH H"); size = 1},
+        0xf5 => { println!("PUSH PSW"); size = 1},
+        _  => { println!("{:x}", opcode); size = 1},
+    }
+
+    size
+}
+
 fn main() {
     let mut input: Vec<u8> = vec![];
 
     let mut counter: usize = 0;
 
+    let mut oplength: usize;
+
     io::stdin()
         .read_to_end(&mut input)
         .unwrap();
@@ -15,18 +50,7 @@ fn main() {
 
     while counter < input.len() {
         // get the instruction
-        let opcode = input[counter];
-        match opcode {
-            0x00 => println!("NOP"),
-            0xc3 => {
-                counter += 1;
-                let low  = input[counter];
-                counter += 1;
-                let high = input[counter];
-                println!("JMP ${:x}{:x}", high, low);
-            }
-            _  => println!("{:x}", opcode),
-        }
-        counter += 1;
+        oplength = opcode(&input, &counter);
+        counter += oplength;
     }
 }