use crate::pack::data;use byteorder::{BigEndian, ByteOrder};use quick_error::quick_error; pub(crate) const N32_SIZE: usize = std::mem::size_of::<u32>(); quick_error! {    #[derive(Debug)]    pub enum Error {        Io(err: std::io::Error, path: std::path::PathBuf) {            display("Could not open pack file at '{}'", path.display())            source(err)        }        Corrupt(msg: String) {            display("{}", msg)        }        UnsupportedVersion(version: u32) {            display("Unsupported pack version: {}", version)        }    }} // Return (data::Kind, num_objects_in_pack)pub fn header(data: &[u8; 12]) -> Result<(data::Kind, u32), Error> {    let mut ofs = 0;    if &data[ofs..ofs + b"PACK".len()] != b"PACK" {        return Err(Error::Corrupt("Pack data type not recognized".into()));    }    ofs += N32_SIZE;    let kind = match BigEndian::read_u32(&data[ofs..ofs + N32_SIZE]) {        2 => data::Kind::V2,        3 => data::Kind::V3,        v => return Err(Error::UnsupportedVersion(v)),    };    ofs += N32_SIZE;    let num_objects = BigEndian::read_u32(&data[ofs..ofs + N32_SIZE]);     Ok((kind, num_objects))}