Read from file or stdin

src/main.rs

@@ -2,21 +2,12 @@ mod colormap;
 
 use std::env;
 use std::fs::File;
-use std::io::prelude::*;
+use std::io::{self, Read};
 
 use colormap::{map_char_to_color, map_u8_to_color};
 
 const GLOBAL_BUFFER_LENGTH: usize = 16;
 
-fn get_file(filename: String) -> File {
-    match File::open(filename) {
-        Ok(f) => f,
-        Err(e) => {
-            panic!("{:?}", e);
-        }
-    }
-}
-
 fn dump_to_hex(bytes: &mut [u8]) -> String {
     let out_vec: Vec<String> = bytes
         .chunks(2)
@@ -38,18 +29,19 @@ fn dump_to_chr(bytes: &mut [u8]) -> String {
 
 fn main() {
     let args: Vec<String> = env::args().collect();
-    if args.len() < 2 {
-        panic!("Not enough arguments!");
-    }
 
-    let filename = &args[1];
-    let mut open_file = get_file(filename.to_string());
+    let mut reader: Box<dyn io::Read> = if args.len() == 1 {
+        Box::new(io::stdin())
+    } else {
+        let filename = &args[1];
+        Box::new(File::open(filename).expect("Could not open file."))
+    };
 
     let mut buf = [0; GLOBAL_BUFFER_LENGTH];
     let mut offset: usize = 0;
 
     loop {
-        let bytes_read = open_file.read(&mut buf);
+        let bytes_read = reader.read(&mut buf);
         match bytes_read {
             Ok(num) => {
                 if num == 0 {