rustutils_cat/
lib.rs

1use clap::Parser;
2use rustutils_runnable::Runnable;
3use std::error::Error;
4use std::fs::File;
5use std::io::{Read, Write};
6use std::path::{Path, PathBuf};
7
8pub const BUFFER_SIZE: usize = 4 * 1024;
9
10/// Concatenate files to standard output.
11#[derive(Parser, Clone, Debug)]
12#[clap(author, version, about, long_about = None)]
13pub struct Cat {
14    /// List of files to concatenate.
15    files: Vec<PathBuf>,
16}
17
18impl Cat {
19    pub fn iter(&self) -> CatIterator {
20        CatIterator::new(self.files.iter().map(|p| p.as_path()))
21    }
22}
23
24#[derive(thiserror::Error, Debug)]
25pub enum CatIteratorError {
26    #[error("Opening file {0:?}: {1:}")]
27    OpeningFile(PathBuf, std::io::Error),
28    #[error("Reading from file {0:?}: {1:}")]
29    ReadingFile(PathBuf, std::io::Error),
30}
31
32pub struct CatIterator<'f> {
33    /// Current file to read from.
34    current: Option<(&'f Path, Box<dyn Read>)>,
35    /// List of files to read still.
36    files: Box<dyn Iterator<Item = &'f Path> + 'f>,
37}
38
39impl<'f> CatIterator<'f> {
40    pub fn new(files: impl Iterator<Item = &'f Path> + 'f) -> Self {
41        CatIterator {
42            current: None,
43            files: Box::new(files),
44        }
45    }
46}
47
48impl<'f> Iterator for CatIterator<'f> {
49    type Item = Result<Vec<u8>, CatIteratorError>;
50    fn next(&mut self) -> Option<Self::Item> {
51        if self.current.is_none() {
52            if let Some(next) = self.files.next() {
53                let reader: Box<dyn Read> = if next.as_os_str() == "-" {
54                    Box::new(std::io::stdin())
55                } else {
56                    match File::open(next) {
57                        Err(error) => {
58                            return Some(Err(CatIteratorError::OpeningFile(
59                                next.to_path_buf(),
60                                error,
61                            )))
62                        }
63                        Ok(file) => Box::new(file),
64                    }
65                };
66                self.current = Some((next, reader));
67            } else {
68                return None;
69            }
70        }
71        let (next, reader) = match &mut self.current {
72            Some((next, reader)) => (next, reader),
73            None => unreachable!(),
74        };
75        let mut buffer = vec![0; BUFFER_SIZE];
76        let length = match reader.read(&mut buffer[..]) {
77            Err(error) => {
78                return Some(Err(CatIteratorError::ReadingFile(
79                    next.to_path_buf(),
80                    error,
81                )))
82            }
83            Ok(length) => length,
84        };
85        buffer.truncate(length);
86        if length == 0 {
87            self.current = None;
88        }
89        Some(Ok(buffer))
90    }
91}
92
93impl Runnable for Cat {
94    fn run(&self) -> Result<(), Box<dyn Error>> {
95        let mut stdout = std::io::stdout();
96        for data in self.iter() {
97            stdout.write_all(&data?)?;
98        }
99        Ok(())
100    }
101}
rustutils_cat/lib.rs

rustutils_cat/
lib.rs
