Playing around with reading bytes

Author: adamkewley

.gitignore

@@ -1,3 +1,3 @@
-
 /target/
 **/*.rs.bk
+master.dat

.idea/fo2dat.iml

@@ -1,3 +1,59 @@
+use std::path::Path;
+use std::fs::File;
+use std::io;
+use std::error::Error;
+use std::io::ErrorKind;
+use std::io::BufReader;
+use std::io::Read;
+
 fn main() {
-    println!("Hello, world!");
+    let usage = "usage: fo2dat DAT_FILE";
+
+    let args: Vec<String> = std::env::args().collect();
+
+    match args.len() {
+        2 => {
+            if let Err(e) = run(&args[1]) {
+                print_and_die(e.description(), 1);
+            }
+        }
+        _ => {
+            print_and_die(usage, 1);
+        }
+    }
 }
+
+fn print_and_die(s: &str, exit_code: i32) {
+    println!("{}", s);
+    std::process::exit(1);
+}
+
+fn run(dat_file_path: &String) -> io::Result<()> {
+    let dat_file_path = Path::new(dat_file_path);
+    let dat_file = File::open(dat_file_path)?;
+
+    let reader = BufReader::new(dat_file);
+
+    let bytes = reader.bytes()
+        .filter(|result| result.is_ok())
+        .map(|result| result.unwrap());
+
+    print_hexdump(bytes);
+
+    Ok(())
+}
+
+fn print_hexdump<I>(iter: I)
+    where I: Iterator<Item = u8>
+{
+    iter.map(|byte| format!("{:02x}", byte))
+        .enumerate()
+        .take(50)
+        .for_each(|(i, hex)| {
+            if i % 5 == 0 {
+                println!("{}", hex);
+            } else {
+                print!("{}", hex);
+            }
+        });
+}