Function unescape

src/testdrive/src/format/bytes.rs:17–31

Unescapes a testdrive byte string. The escape character is `\` and the only interesting escape sequence is `\xNN`, where each `N` is a valid hexadecimal digit. All other characters following a backslash are taken literally.

(s: &[u8])

/// `\xNN`, where each `N` is a valid hexadecimal digit. All other characters
/// following a backslash are taken literally.
pub fn unescape(s: &[u8]) -> Result<Vec<u8>, anyhow::Error> {
    let mut out = vec![];
    let mut s = s.iter().copied().fuse();
    while let Some(b) = s.next() {
        match b {
            b'\\' if s.next() == Some(b'x') => match (next_hex(&mut s), next_hex(&mut s)) {
                (Some(c1), Some(c0)) => out.push((c1 << 4) + c0),
                _ => bail!("invalid hexadecimal escape"),
            },
            b'\\' => continue,
            _ => out.push(b),
        }
    }
    Ok(out)
}

/// Retrieves the value of the next hexadecimal digit in `iter`, if the next
/// byte is a valid hexadecimal digit.