rsv_lib/io/
slice.rs

1use crate::args::Slice;
2use crate::utils::cli_result::CliResult;
3use crate::utils::filename::new_file;
4use crate::utils::writer::Writer;
5use std::io::BufRead;
6use std::io::{stdin, BufReader, Stdin};
7
8impl Slice {
9    pub fn io_run(&self) -> CliResult {
10        // current file
11        let out_path = new_file("sliced.csv");
12
13        // open file
14        let mut wtr = Writer::file_or_stdout(self.export, &out_path)?;
15        let mut rdr = BufReader::new(stdin());
16
17        // header
18        if !self.no_header {
19            let mut buf = vec![];
20            rdr.read_until(b'\n', &mut buf)?;
21            wtr.write_bytes_unchecked(&buf);
22        }
23
24        // slice
25        match self.index {
26            Some(index) => write_by_index(&mut rdr, &mut wtr, index),
27            None => {
28                let e = self
29                    .end
30                    .or_else(|| self.length.map(|l| self.start + l))
31                    .unwrap_or(usize::MAX - 10);
32                write_by_range(&mut rdr, &mut wtr, self.start, e);
33            }
34        }
35
36        if self.export {
37            println!("Saved to file: {}", out_path.display())
38        }
39
40        Ok(())
41    }
42}
43
44fn write_by_index(rdr: &mut BufReader<Stdin>, wtr: &mut Writer, index: usize) {
45    let mut buf = vec![];
46    let mut n = 0;
47
48    while let Ok(bytes) = rdr.read_until(b'\n', &mut buf) {
49        if bytes == 0 {
50            break;
51        }
52        if n == index {
53            wtr.write_bytes_unchecked(&buf[..bytes]);
54            break;
55        }
56        buf.clear();
57        n += 1;
58    }
59}
60
61fn write_by_range(rdr: &mut BufReader<Stdin>, wtr: &mut Writer, start: usize, end: usize) {
62    let mut buf = vec![];
63    let mut n = 0;
64
65    while let Ok(bytes) = rdr.read_until(b'\n', &mut buf) {
66        if bytes == 0 || n >= end {
67            break;
68        }
69        if n >= start && n < end {
70            wtr.write_bytes_unchecked(&buf[..bytes]);
71        }
72        buf.clear();
73        n += 1;
74    }
75}
rsv_lib/io/slice.rs

rsv_lib/io/
slice.rs
