Function nom::multi::length_value

pub fn length_value<I, O, N, E, F, G>(
    f: F,
    g: G,
) -> impl FnMut(I) -> IResult<I, O, E>
where
    I: Clone + InputLength + InputTake,
    N: ToUsize,
    F: Parser<I, N, E>,
    G: Parser<I, O, E>,
    E: ParseError<I>,

Gets a number from the first parser, takes a subslice of the input of that size, then applies the second parser on that subslice. If the second parser returns Incomplete, length_value will return an error.

Arguments

• f The parser to apply.
• g The parser to apply on the subslice.

use nom::number::complete::be_u16;
use nom::multi::length_value;
use nom::bytes::complete::tag;

fn parser(s: &[u8]) -> IResult<&[u8], &[u8]> {
  length_value(be_u16, tag("abc"))(s)
}

assert_eq!(parser(b"\x00\x03abcefg"), Ok((&b"efg"[..], &b"abc"[..])));
assert_eq!(parser(b"\x00\x03123123"), Err(Err::Error(Error::new(&b"123"[..], ErrorKind::Tag))));
assert_eq!(parser(b"\x00\x03a"), Err(Err::Incomplete(Needed::new(2))));