It works!!!

src/main.rs

@@ -1,12 +1,15 @@
 extern crate getopts;
+extern crate byteorder;
 
 use std::env;
 use std::fs;
 use std::io::BufReader;
 use std::io::prelude::*;
 use std::i32;
+use std::io::Cursor;
 
 use getopts::Options;
+use byteorder::{ReadBytesExt, WriteBytesExt, LittleEndian};
 
 
 fn main() {
@@ -56,20 +59,31 @@ fn create(input: &String, output: &String) {
             }
         }
 
-        output_file.write_all(&[i as u8]).unwrap();
+        let mut out : Vec<u8> = vec![];
+
+        out.write_i32::<LittleEndian>(i).unwrap();
+
+        output_file.write_all(&out).unwrap();
     }
 }
 
 fn extract(input: &String, output: &String) {
     let mut output_file = fs::File::create(output).unwrap();
+    let mut input_file = fs::File::open(input).unwrap();
 
-    let input_file = fs::File::open(input).unwrap();
-    let input_buf = BufReader::new(input_file);
+    let mut buf = vec![0; 4];
 
-    for b in input_buf.bytes() {
-        let b = b.unwrap();
+    loop {
+        let size = input_file.read(&mut buf).unwrap();
 
-        output_file.write(&[get_byte(b as i32)]).unwrap();
+        if size <= 0 {
+            break;
+        }
+
+        let mut c = Cursor::new(&buf);
+        let index = c.read_i32::<LittleEndian>().unwrap();
+
+        output_file.write_all(&[get_byte(index)]).unwrap();
     }
 }