src/vendor/quick-error/examples/context.rs

   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
  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
  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 }