| use quick_error::{quick_error, ResultExt}; |
| use std::env; |
| use std::fs::File; |
| use std::io::{self, stderr, Read, Write}; |
| use std::num::ParseIntError; |
| use std::path::{Path, PathBuf}; |
| |
| quick_error! { |
| #[derive(Debug)] |
| pub enum Error { |
| NoFileName {} |
| Io(err: io::Error, path: PathBuf) { |
| display("could not read file {:?}: {}", path, err) |
| context(path: &'a Path, err: io::Error) |
| -> (err, path.to_path_buf()) |
| } |
| Parse(err: ParseIntError, path: PathBuf) { |
| display("could not parse file {:?}: {}", path, err) |
| context(path: &'a Path, err: ParseIntError) |
| -> (err, path.to_path_buf()) |
| } |
| } |
| } |
| |
| fn parse_file() -> Result<u64, Error> { |
| let fname = env::args().skip(1).next().ok_or(Error::NoFileName)?; |
| let fname = Path::new(&fname); |
| let mut file = File::open(fname).context(fname)?; |
| let mut buf = String::new(); |
| file.read_to_string(&mut buf).context(fname)?; |
| Ok(buf.parse().context(fname)?) |
| } |
| |
| fn main() { |
| match parse_file() { |
| Ok(val) => { |
| println!("Read: {}", val); |
| } |
| Err(e) => { |
| writeln!(&mut stderr(), "Error: {}", e).ok(); |
| } |
| } |
| } |