Function byte_lut

pub fn byte_lut<T: Copy>(
    lut: &[Option<T>; 256],
    error: ParseError,
) -> ByteLut<'_, T>

Parser that consumes a single byte and maps it using a lookup table.

Equivalent to parser::byte().map_res(|b| LOOKUP[b as usize].ok_or("expected ...")), which is usually faster than an equivalent match statement in the closure.

See also parser::byte_map! which wraps this function, allowing a match-like syntax to be used to define the lookup table.

Examples

const LOOKUP: [Option<bool>; 256] = {
    let mut x = [None; 256];
    x['#' as usize] = Some(true);
    x['.' as usize] = Some(false);
    x
};

let parser = parser::byte_lut(&LOOKUP, ParseError::Custom("expected '#' or '.'"));
assert_eq!(parser.parse(b"#..##"), Ok((true, &b"..##"[..])));
assert_eq!(parser.parse(b"..##"), Ok((false, &b".##"[..])));
assert_eq!(parser.parse(b"abc"), Err((ParseError::Custom("expected '#' or '.'"), &b"abc"[..])));