ex_cli/util/
file.rs

1use crate::error::MyResult;
2use std::io::Read;
3
4pub fn read_until(
5    file: &mut dyn Read,
6    buffer: &mut Vec<u8>,
7    size: usize,
8) -> MyResult<usize> {
9    if let Some(size) = size.checked_sub(buffer.len()) {
10        if size > 0 {
11            file.take(size as u64).read_to_end(buffer)?;
12        }
13    }
14    Ok(buffer.len())
15}
16
17#[cfg(test)]
18mod tests {
19    use crate::error::MyResult;
20    use crate::util::file::read_until;
21    use pretty_assertions::assert_eq;
22    use std::io::Cursor;
23
24    #[test]
25    fn test_zero_bytes_are_not_read() -> MyResult<()> {
26        let (count, buffer) = read_until_multi(vec![0])?;
27        assert_eq!(count, 0);
28        assert_eq!(&buffer, b"");
29        Ok(())
30    }
31
32    #[test]
33    fn test_counted_bytes_are_partly_read() -> MyResult<()> {
34        let (count, buffer) = read_until_multi(vec![4])?;
35        assert_eq!(count, 4);
36        assert_eq!(&buffer, b"ABCD");
37        Ok(())
38    }
39
40    #[test]
41    fn test_counted_bytes_are_fully_read() -> MyResult<()> {
42        let (count, buffer) = read_until_multi(vec![12])?;
43        assert_eq!(count, 10);
44        assert_eq!(&buffer, b"ABCDEFGHIJ");
45        Ok(())
46    }
47
48    #[test]
49    fn test_counted_bytes_are_partly_and_partly_read() -> MyResult<()> {
50        let (count, buffer) = read_until_multi(vec![8, 4])?;
51        assert_eq!(count, 8);
52        assert_eq!(&buffer, b"ABCDEFGH");
53        Ok(())
54    }
55
56    #[test]
57    fn test_counted_bytes_are_partly_and_fully_read() -> MyResult<()> {
58        let (count, buffer) = read_until_multi(vec![4, 12])?;
59        assert_eq!(count, 10);
60        assert_eq!(&buffer, b"ABCDEFGHIJ");
61        Ok(())
62    }
63
64    fn read_until_multi(sizes: Vec<usize>) -> MyResult<(usize, Vec<u8>)> {
65        let mut file = Cursor::new(b"ABCDEFGHIJ".to_vec());
66        let mut buffer = Vec::new();
67        let mut count = 0;
68        for size in sizes {
69            count = read_until(&mut file, &mut buffer, size)?;
70        }
71        Ok((count, buffer))
72    }
73}
ex_cli/util/file.rs

ex_cli/util/
file.rs
