It works!!!

Cargo.lock

@@ -2,9 +2,15 @@
 name = "picomp"
 version = "0.1.0"
 dependencies = [
+ "byteorder 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "getopts 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "byteorder"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "getopts"
 version = "0.2.14"

Cargo.toml

@@ -5,3 +5,4 @@ authors = ["logaritmisk <anders.e.olsson@gmail.com>"]
 
 [dependencies]
 getopts = "0.2"
+byteorder = "0.5"

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();
     }
 }