//! Encoding utilitiesuse std::io::{self, Write}; use bstr::{BString, ByteSlice}; /// An error returned when object encoding fails.#[derive(Debug, thiserror::Error)]#[allow(missing_docs)]pub enum Error {    #[error("Newlines are not allowed in header values: {value:?}")]    NewlineInHeaderValue { value: BString },    #[error("Header values must not be empty")]    EmptyValue,} macro_rules! check {    ($e: expr) => {        $e.expect("Writing to a Vec should never fail.")    };}/// Generates a loose header bufferpub fn loose_header(kind: crate::Kind, size: usize) -> smallvec::SmallVec<[u8; 28]> {    let mut v = smallvec::SmallVec::new();    check!(v.write_all(kind.as_bytes()));    check!(v.write_all(SPACE));    check!(v.write_all(itoa::Buffer::new().format(size).as_bytes()));    check!(v.write_all(b"\0"));    v} impl From<Error> for io::Error {    fn from(other: Error) -> io::Error {        io::Error::new(io::ErrorKind::Other, other)    }} pub(crate) fn header_field_multi_line(name: &[u8], value: &[u8], mut out: impl io::Write) -> io::Result<()> {    let mut lines = value.as_bstr().split_str(b"\n");    trusted_header_field(name, lines.next().ok_or(Error::EmptyValue)?, &mut out)?;    for line in lines {        out.write_all(SPACE)?;        out.write_all(line)?;        out.write_all(NL)?;    }    Ok(())} pub(crate) 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(crate) 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(crate) 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(crate) 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: value.into() }.into());    }    trusted_header_field(name, value, out)} pub(crate) const NL: &[u8; 1] = b"\n";pub(crate) const SPACE: &[u8; 1] = b" ";