use nom::{    branch::alt,    bytes::complete::{tag, take_till1},    combinator::all_consuming,    error::ParseError,    sequence::pair,    IResult,}; use crate::bstr::{BStr, ByteSlice}; pub(crate) fn newline<'a, E: ParseError<&'a [u8]>>(i: &'a [u8]) -> IResult<&'a [u8], &'a [u8], E> {    alt((tag(b"\r\n"), tag(b"\n")))(i)} fn subject_and_body<'a, E: ParseError<&'a [u8]>>(i: &'a [u8]) -> IResult<&'a [u8], (&'a BStr, Option<&'a BStr>), E> {    let mut c = i;    let mut consumed_bytes = 0;    while !c.is_empty() {        c = match take_till1::<_, _, E>(|c| c == b'\n' || c == b'\r')(c) {            Ok((i1, segment)) => {                consumed_bytes += segment.len();                match pair::<_, _, _, E, _, _>(newline, newline)(i1) {                    Ok((body, _)) => {                        return Ok((                            &[],                            (                                i[0usize..consumed_bytes].as_bstr(),                                (!body.is_empty()).then(|| body.as_bstr()),                            ),                        ));                    }                    Err(_) => match i1.get(1..) {                        Some(next) => {                            consumed_bytes += 1;                            next                        }                        None => break,                    },                }            }            Err(_) => match c.get(1..) {                Some(next) => {                    consumed_bytes += 1;                    next                }                None => break,            },        };    }    Ok((&[], (i.as_bstr(), None)))} /// Returns title and body, without separatorpub fn message(input: &[u8]) -> (&BStr, Option<&BStr>) {    all_consuming(subject_and_body::<()>)(input).expect("cannot fail").1}