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use std::io;
use gix_features::decode::{leb64, leb64_from_read};
use super::{BLOB, COMMIT, OFS_DELTA, REF_DELTA, TAG, TREE};
use crate::data;
/// Decoding
impl 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: gix_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 = gix_hash::Kind::buf();
let hash = &mut buf[..hash_len];
r.read_exact(hash)?;
#[allow(clippy::redundant_slicing)]
let delta = RefDelta {
base_id: gix_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)
}
|
