use crate::pack::data;use byteorder::{BigEndian, ByteOrder}; pub(crate) const N32_SIZE: usize = std::mem::size_of::<u32>(); #[derive(thiserror::Error, Debug)]pub enum Error {    #[error("Could not open pack file at '{path}'")]    Io {        source: std::io::Error,        path: std::path::PathBuf,    },    #[error("{0}")]    Corrupt(String),    #[error("Unsupported pack version: {0}")]    UnsupportedVersion(u32),} // 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))}