1 #[macro_use(quick_error)] extern crate quick_error;
2
3 use std::io::{self, stderr, Read, Write};
4 use std::fs::File;
5 use std::env;
6 use std::num::ParseIntError;
7 use std::path::{Path, PathBuf};
8
9 use quick_error::ResultExt;
10
11 quick_error! {
12 #[derive(Debug)]
13 pub enum Error {
14 NoFileName {
15 description("no file name specified")
16 }
17 Io(err: io::Error, path: PathBuf) {
18 display("could not read file {:?}: {}", path, err)
19 context(path: &'a Path, err: io::Error)
20 -> (err, path.to_path_buf())
21 }
22 Parse(err: ParseIntError, path: PathBuf) {
23 display("could not parse file {:?}: {}", path, err)
24 context(path: &'a Path, err: ParseIntError)
25 -> (err, path.to_path_buf())
26 }
27 }
28 }
29
parse_file() -> Result<u64, Error>30 fn parse_file() -> Result<u64, Error> {
31 let fname = try!(env::args().skip(1).next().ok_or(Error::NoFileName));
32 let fname = Path::new(&fname);
33 let mut file = try!(File::open(fname).context(fname));
34 let mut buf = String::new();
35 try!(file.read_to_string(&mut buf).context(fname));
36 Ok(try!(buf.parse().context(fname)))
37 }
38
main()39 fn main() {
40 match parse_file() {
41 Ok(val) => {
42 println!("Read: {}", val);
43 }
44 Err(e) => {
45 writeln!(&mut stderr(), "Error: {}", e).ok();
46 }
47 }
48 }
49