use std::io; use git_features::decode::{leb64, leb64_from_read}; use super::{BLOB, COMMIT, OFS_DELTA, REF_DELTA, TAG, TREE};use crate::data; /// Decodingimpl data::Entry {    /// Decode an entry from the given entry data `d`, providing the `pack_offset` to allow tracking the start of the entry data section.    ///    /// # Panics    ///    /// If we cannot understand the header, garbage data is likely to trigger this.    pub fn from_bytes(d: &[u8], pack_offset: data::Offset, hash_len: usize) -> data::Entry {        let (type_id, size, mut consumed) = parse_header_info(d);         use crate::data::entry::Header::*;        let object = match type_id {            OFS_DELTA => {                let (distance, leb_bytes) = leb64(&d[consumed..]);                let delta = OfsDelta {                    base_distance: distance,                };                consumed += leb_bytes;                delta            }            REF_DELTA => {                let delta = RefDelta {                    base_id: git_hash::ObjectId::from(&d[consumed..][..hash_len]),                };                consumed += hash_len;                delta            }            BLOB => Blob,            TREE => Tree,            COMMIT => Commit,            TAG => Tag,            _ => panic!("We currently don't support any V3 features or extensions"),        };        data::Entry {            header: object,            decompressed_size: size,            data_offset: pack_offset + consumed as u64,        }    }     /// Instantiate an `Entry` from the reader `r`, providing the `pack_offset` to allow tracking the start of the entry data section.    pub fn from_read(        mut r: impl io::Read,        pack_offset: data::Offset,        hash_len: usize,    ) -> Result<data::Entry, io::Error> {        let (type_id, size, mut consumed) = streaming_parse_header_info(&mut r)?;         use crate::data::entry::Header::*;        let object = match type_id {            OFS_DELTA => {                let (distance, leb_bytes) = leb64_from_read(&mut r)?;                let delta = OfsDelta {                    base_distance: distance,                };                consumed += leb_bytes;                delta            }            REF_DELTA => {                let mut buf = git_hash::Kind::buf();                let hash = &mut buf[..hash_len];                r.read_exact(hash)?;                #[allow(clippy::redundant_slicing)]                let delta = RefDelta {                    base_id: git_hash::ObjectId::from(&hash[..]),                };                consumed += hash_len;                delta            }            BLOB => Blob,            TREE => Tree,            COMMIT => Commit,            TAG => Tag,            _ => panic!("We currently don't support any V3 features or extensions"),        };        Ok(data::Entry {            header: object,            decompressed_size: size,            data_offset: pack_offset + consumed as u64,        })    }} #[inline]fn streaming_parse_header_info(mut read: impl io::Read) -> Result<(u8, u64, usize), io::Error> {    let mut byte = [0u8; 1];    read.read_exact(&mut byte)?;    let mut c = byte[0];    let mut i = 1;    let type_id = (c >> 4) & 0b0000_0111;    let mut size = c as u64 & 0b0000_1111;    let mut s = 4;    while c & 0b1000_0000 != 0 {        read.read_exact(&mut byte)?;        c = byte[0];        i += 1;        size += ((c & 0b0111_1111) as u64) << s;        s += 7    }    Ok((type_id, size, i))} /// Parses the header of a pack-entry, yielding object type id, decompressed object size, and consumed bytes#[inline]fn parse_header_info(data: &[u8]) -> (u8, u64, usize) {    let mut c = data[0];    let mut i = 1;    let type_id = (c >> 4) & 0b0000_0111;    let mut size = c as u64 & 0b0000_1111;    let mut s = 4;    while c & 0b1000_0000 != 0 {        c = data[i];        i += 1;        size += ((c & 0b0111_1111) as u64) << s;        s += 7    }    (type_id, size, i)}