use std::io; use super::{BLOB, COMMIT, OFS_DELTA, REF_DELTA, SHA1_SIZE, 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: u64) -> 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) = leb64decode(&d[consumed..]); let delta = OfsDelta { base_distance: distance, }; consumed += leb_bytes; delta } REF_DELTA => { let delta = RefDelta { base_id: git_hash::ObjectId::from_20_bytes(&d[consumed..consumed + SHA1_SIZE]), }; consumed += SHA1_SIZE; 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: u64) -> 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) = streaming_leb64decode(&mut r)?; let delta = OfsDelta { base_distance: distance, }; consumed += leb_bytes; delta } REF_DELTA => { let mut buf = [0u8; SHA1_SIZE]; r.read_exact(&mut buf)?; let delta = RefDelta { base_id: git_hash::ObjectId::new_sha1(buf), }; consumed += SHA1_SIZE; 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_leb64decode(mut r: impl io::Read) -> Result<(u64, usize), io::Error> { let mut b = [0u8; 1]; let mut i = 0; r.read_exact(&mut b)?; i += 1; let mut value = b[0] as u64 & 0x7f; while b[0] & 0x80 != 0 { r.read_exact(&mut b)?; i += 1; value += 1; value = (value << 7) + (b[0] as u64 & 0x7f) } Ok((value, i))} #[inline]fn leb64decode(d: &[u8]) -> (u64, usize) { let mut i = 0; let mut c = d[i]; i += 1; let mut value = c as u64 & 0x7f; while c & 0x80 != 0 { c = d[i]; i += 1; value += 1; value = (value << 7) + (c as u64 & 0x7f) } (value, i)} #[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)}
use std::io;
use super::{BLOB, COMMIT, OFS_DELTA, REF_DELTA, SHA1_SIZE, 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: u64) -> 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) = leb64decode(&d[consumed..]);
let delta = OfsDelta {
base_distance: distance,
};
consumed += leb_bytes;
delta
}
REF_DELTA => {
let delta = RefDelta {
base_id: git_hash::ObjectId::from_20_bytes(&d[consumed..consumed + SHA1_SIZE]),
};
consumed += SHA1_SIZE;
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: u64) -> 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) = streaming_leb64decode(&mut r)?;
let delta = OfsDelta {
base_distance: distance,
};
consumed += leb_bytes;
delta
}
REF_DELTA => {
let mut buf = [0u8; SHA1_SIZE];
r.read_exact(&mut buf)?;
let delta = RefDelta {
base_id: git_hash::ObjectId::new_sha1(buf),
};
consumed += SHA1_SIZE;
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_leb64decode(mut r: impl io::Read) -> Result<(u64, usize), io::Error> {
let mut b = [0u8; 1];
let mut i = 0;
r.read_exact(&mut b)?;
i += 1;
let mut value = b[0] as u64 & 0x7f;
while b[0] & 0x80 != 0 {
r.read_exact(&mut b)?;
i += 1;
value += 1;
value = (value << 7) + (b[0] as u64 & 0x7f)
}
Ok((value, i))
}
#[inline]
fn leb64decode(d: &[u8]) -> (u64, usize) {
let mut i = 0;
let mut c = d[i];
i += 1;
let mut value = c as u64 & 0x7f;
while c & 0x80 != 0 {
c = d[i];
i += 1;
value += 1;
value = (value << 7) + (c as u64 & 0x7f)
}
(value, i)
}
#[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)
}