It works!... not. Cant cast i32 to u8...

src/main.rs

@@ -1,16 +1,47 @@
+extern crate getopts;
+
 use std::env;
 use std::fs;
 use std::io::BufReader;
 use std::io::prelude::*;
 use std::i32;
 
+use getopts::Options;
+
 
 fn main() {
-    let output_filename = env::args().nth(1).unwrap();
-    let mut output_file = fs::File::create(output_filename).unwrap();
+    let args: Vec<String> = env::args().collect();
 
-    let input_filename = env::args().nth(2).unwrap();
-    let input_file = fs::File::open(input_filename).unwrap();
+    let mut opts = Options::new();
+
+    opts.optflag("c", "", "create file");
+    opts.optflag("x", "", "extract file");
+    opts.optopt("i", "", "input file", "NAME");
+    opts.optopt("o", "", "output file", "NAME");
+
+    let matches = match opts.parse(&args[1..]) {
+        Ok(m) => { m }
+        Err(f) => { panic!(f.to_string()) }
+    };
+
+    if matches.opt_present("c") {
+        let input = matches.opt_str("i").unwrap();
+        let output = matches.opt_str("o").unwrap();
+
+        create(&input, &output);
+    }
+    else if matches.opt_present("x") {
+        let input = matches.opt_str("i").unwrap();
+        let output = matches.opt_str("o").unwrap();
+
+        extract(&input, &output)
+    }
+}
+
+fn create(input: &String, output: &String) {
+    let mut output_file = fs::File::create(output).unwrap();
+
+    let input_file = fs::File::open(input).unwrap();
     let input_buf = BufReader::new(input_file);
 
     let mut i : i32 = 0;
@@ -25,7 +56,20 @@ fn main() {
             }
         }
 
-        output_file.write(&[i as u8]).unwrap();
+        output_file.write_all(&[i as u8]).unwrap();
+    }
+}
+
+fn extract(input: &String, output: &String) {
+    let mut output_file = fs::File::create(output).unwrap();
+
+    let input_file = fs::File::open(input).unwrap();
+    let input_buf = BufReader::new(input_file);
+
+    for b in input_buf.bytes() {
+        let b = b.unwrap();
+
+        output_file.write(&[get_byte(b as i32)]).unwrap();
     }
 }