use std::io; use bstr::{BString, ByteSlice};use quick_error::quick_error; quick_error! {    #[derive(Debug)]    enum Error {        NewlineInHeaderValue(value: BString) {            display("Newlines are not allowed in header values: {:?}", value)        }        EmptyValue {            display("Header values must not be empty")        }    }} impl From<Error> for io::Error {    fn from(other: Error) -> io::Error {        io::Error::new(io::ErrorKind::Other, other)    }} pub fn header_field_multi_line(name: &[u8], value: &[u8], mut out: impl io::Write) -> io::Result<()> {    let mut lines = value.as_bstr().lines();    trusted_header_field(name, lines.next().expect("non-empty value"), &mut out)?;    for line in lines {        out.write_all(SPACE)?;        out.write_all(line)?;        out.write_all(NL)?;    }    // If the last line ended on a newline, we have to re-add it by force    if let Some(b) = value.last() {        if *b == b'\n' {            out.write_all(SPACE)?;            out.write_all(NL)?;        }    }    Ok(())} pub fn trusted_header_field(name: &[u8], value: &[u8], mut out: impl io::Write) -> io::Result<()> {    out.write_all(name)?;    out.write_all(SPACE)?;    out.write_all(value)?;    out.write_all(NL)} pub fn trusted_header_signature(    name: &[u8],    value: &git_actor::SignatureRef<'_>,    mut out: impl io::Write,) -> io::Result<()> {    out.write_all(name)?;    out.write_all(SPACE)?;    value.write_to(&mut out)?;    out.write_all(NL)} pub fn trusted_header_id(name: &[u8], value: &git_hash::ObjectId, mut out: impl io::Write) -> io::Result<()> {    out.write_all(name)?;    out.write_all(&SPACE[..])?;    value.write_hex_to(&mut out)?;    out.write_all(&NL[..])} pub fn header_field(name: &[u8], value: &[u8], out: impl io::Write) -> io::Result<()> {    if value.is_empty() {        return Err(Error::EmptyValue.into());    }    if value.find(NL).is_some() {        return Err(Error::NewlineInHeaderValue(value.into()).into());    }    trusted_header_field(name, value, out)} pub(crate) const NL: &[u8; 1] = b"\n";pub(crate) const SPACE: &[u8; 1] = b" ";