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use crate::data;
pub(crate) const N32_SIZE: usize = std::mem::size_of::<u32>();
/// Parses the first 12 bytes of a pack file, returning the pack version as well as the number of objects contained in the pack.
pub fn decode(data: &[u8; 12]) -> Result<(data::Version, u32), decode::Error> {
let mut ofs = 0;
if &data[ofs..ofs + b"PACK".len()] != b"PACK" {
return Err(decode::Error::Corrupt("Pack data type not recognized".into()));
}
ofs += N32_SIZE;
let kind = match crate::read_u32(&data[ofs..ofs + N32_SIZE]) {
2 => data::Version::V2,
3 => data::Version::V3,
v => return Err(decode::Error::UnsupportedVersion(v)),
};
ofs += N32_SIZE;
let num_objects = crate::read_u32(&data[ofs..ofs + N32_SIZE]);
Ok((kind, num_objects))
}
/// Write a pack data header at `version` with `num_objects` and return a buffer.
pub fn encode(version: data::Version, num_objects: u32) -> [u8; 12] {
use crate::data::Version::*;
let mut buf = [0u8; 12];
buf[..4].copy_from_slice(b"PACK");
buf[4..8].copy_from_slice(
&match version {
V2 => 2u32,
V3 => 3,
}
.to_be_bytes()[..],
);
buf[8..].copy_from_slice(&num_objects.to_be_bytes()[..]);
buf
}
///
pub mod decode {
/// Returned by [`decode()`][super::decode()].
#[derive(thiserror::Error, Debug)]
#[allow(missing_docs)]
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),
}
}
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