# pack.py -- For dealing with packed git objects.
# Copyright (C) 2007 James Westby <jw+debian@jameswestby.net>
# Copyright (C) 2008-2013 Jelmer Vernooij <jelmer@jelmer.uk>
#
# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
# General Public License as public by the Free Software Foundation; version 2.0
# or (at your option) any later version. You can redistribute it and/or
# modify it under the terms of either of these two licenses.
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# You should have received a copy of the licenses; if not, see
# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
# License, Version 2.0.
#
"""Classes for dealing with packed git objects.
A pack is a compact representation of a bunch of objects, stored
using deltas where possible.
They have two parts, the pack file, which stores the data, and an index
that tells you where the data is.
To find an object you look in all of the index files 'til you find a
match for the object name. You then use the pointer got from this as
a pointer in to the corresponding packfile.
"""
from collections import defaultdict
import binascii
from io import BytesIO, UnsupportedOperation
from collections import (
deque,
)
try:
from cdifflib import CSequenceMatcher as SequenceMatcher
except ModuleNotFoundError:
from difflib import SequenceMatcher
import struct
from itertools import chain
import os
import sys
from typing import Optional, Callable, Tuple, List, Deque, Union, Protocol, Iterable, Iterator, Dict
import warnings
from hashlib import sha1
from os import (
SEEK_CUR,
SEEK_END,
)
from struct import unpack_from
import zlib
try:
import mmap
except ImportError:
has_mmap = False
else:
has_mmap = True
# For some reason the above try, except fails to set has_mmap = False for plan9
if sys.platform == "Plan9":
has_mmap = False
from dulwich.errors import (
ApplyDeltaError,
ChecksumMismatch,
)
from dulwich.file import GitFile
from dulwich.lru_cache import (
LRUSizeCache,
)
from dulwich.objects import (
ShaFile,
hex_to_sha,
sha_to_hex,
object_header,
)
OFS_DELTA = 6
REF_DELTA = 7
DELTA_TYPES = (OFS_DELTA, REF_DELTA)
DEFAULT_PACK_DELTA_WINDOW_SIZE = 10
OldUnpackedObject = Union[Tuple[Union[bytes, int], List[bytes]], List[bytes]]
ResolveExtRefFn = Callable[[bytes], Tuple[int, OldUnpackedObject]]
ProgressFn = Callable[[int, str], None]
class ObjectContainer(Protocol):
def add_object(self, obj: ShaFile) -> None:
"""Add a single object to this object store."""
def add_objects(
self, objects: Iterable[Tuple[ShaFile, Optional[str]]],
progress: Optional[Callable[[str], None]] = None) -> None:
"""Add a set of objects to this object store.
Args:
objects: Iterable over a list of (object, path) tuples
"""
def __contains__(self, sha1: bytes) -> bool:
"""Check if a hex sha is present."""
def __getitem__(self, sha1: bytes) -> ShaFile:
"""Retrieve an object."""
class PackedObjectContainer(ObjectContainer):
def get_raw_unresolved(self, sha1: bytes) -> Tuple[int, Optional[bytes], List[bytes]]:
"""Get a raw unresolved object."""
raise NotImplementedError(self.get_raw_unresolved)
def take_msb_bytes(read: Callable[[int], bytes], crc32: Optional[int] = None) -> Tuple[List[int], Optional[int]]:
"""Read bytes marked with most significant bit.
Args:
read: Read function
"""
ret: List[int] = []
while len(ret) == 0 or ret[-1] & 0x80:
b = read(1)
if crc32 is not None:
crc32 = binascii.crc32(b, crc32)
ret.append(ord(b[:1]))
return ret, crc32
class PackFileDisappeared(Exception):
def __init__(self, obj):
self.obj = obj
class UnpackedObject:
"""Class encapsulating an object unpacked from a pack file.
These objects should only be created from within unpack_object. Most
members start out as empty and are filled in at various points by
read_zlib_chunks, unpack_object, DeltaChainIterator, etc.
End users of this object should take care that the function they're getting
this object from is guaranteed to set the members they need.
"""
__slots__ = [
"offset", # Offset in its pack.
"_sha", # Cached binary SHA.
"obj_type_num", # Type of this object.
"obj_chunks", # Decompressed and delta-resolved chunks.
"pack_type_num", # Type of this object in the pack (may be a delta).
"delta_base", # Delta base offset or SHA.
"comp_chunks", # Compressed object chunks.
"decomp_chunks", # Decompressed object chunks.
"decomp_len", # Decompressed length of this object.
"crc32", # CRC32.
]
obj_type_num: Optional[int]
obj_chunks: Optional[List[bytes]]
# TODO(dborowitz): read_zlib_chunks and unpack_object could very well be
# methods of this object.
def __init__(self, pack_type_num, delta_base, decomp_len, crc32):
self.offset = None
self._sha = None
self.pack_type_num = pack_type_num
self.delta_base = delta_base
self.comp_chunks = None
self.decomp_chunks: List[bytes] = []
self.decomp_len = decomp_len
self.crc32 = crc32
if pack_type_num in DELTA_TYPES:
self.obj_type_num = None
self.obj_chunks = None
else:
self.obj_type_num = pack_type_num
self.obj_chunks = self.decomp_chunks
self.delta_base = delta_base
def sha(self):
"""Return the binary SHA of this object."""
if self._sha is None:
self._sha = obj_sha(self.obj_type_num, self.obj_chunks)
return self._sha
def sha_file(self):
"""Return a ShaFile from this object."""
assert self.obj_type_num is not None and self.obj_chunks is not None
return ShaFile.from_raw_chunks(self.obj_type_num, self.obj_chunks)
# Only provided for backwards compatibility with code that expects either
# chunks or a delta tuple.
def _obj(self) -> OldUnpackedObject:
"""Return the decompressed chunks, or (delta base, delta chunks)."""
if self.pack_type_num in DELTA_TYPES:
assert isinstance(self.delta_base, (bytes, int))
return (self.delta_base, self.decomp_chunks)
else:
return self.decomp_chunks
def __eq__(self, other):
if not isinstance(other, UnpackedObject):
return False
for slot in self.__slots__:
if getattr(self, slot) != getattr(other, slot):
return False
return True
def __ne__(self, other):
return not (self == other)
def __repr__(self):
data = ["{}={!r}".format(s, getattr(self, s)) for s in self.__slots__]
return "{}({})".format(self.__class__.__name__, ", ".join(data))
_ZLIB_BUFSIZE = 4096
def read_zlib_chunks(
read_some: Callable[[int], bytes],
unpacked: UnpackedObject, include_comp: bool = False,
buffer_size: int = _ZLIB_BUFSIZE
) -> bytes:
"""Read zlib data from a buffer.
This function requires that the buffer have additional data following the
compressed data, which is guaranteed to be the case for git pack files.
Args:
read_some: Read function that returns at least one byte, but may
return less than the requested size.
unpacked: An UnpackedObject to write result data to. If its crc32
attr is not None, the CRC32 of the compressed bytes will be computed
using this starting CRC32.
After this function, will have the following attrs set:
* comp_chunks (if include_comp is True)
* decomp_chunks
* decomp_len
* crc32
include_comp: If True, include compressed data in the result.
buffer_size: Size of the read buffer.
Returns: Leftover unused data from the decompression.
Raises:
zlib.error: if a decompression error occurred.
"""
if unpacked.decomp_len <= -1:
raise ValueError("non-negative zlib data stream size expected")
decomp_obj = zlib.decompressobj()
comp_chunks = []
decomp_chunks = unpacked.decomp_chunks
decomp_len = 0
crc32 = unpacked.crc32
while True:
add = read_some(buffer_size)
if not add:
raise zlib.error("EOF before end of zlib stream")
comp_chunks.append(add)
decomp = decomp_obj.decompress(add)
decomp_len += len(decomp)
decomp_chunks.append(decomp)
unused = decomp_obj.unused_data
if unused:
left = len(unused)
if crc32 is not None:
crc32 = binascii.crc32(add[:-left], crc32)
if include_comp:
comp_chunks[-1] = add[:-left]
break
elif crc32 is not None:
crc32 = binascii.crc32(add, crc32)
if crc32 is not None:
crc32 &= 0xFFFFFFFF
if decomp_len != unpacked.decomp_len:
raise zlib.error("decompressed data does not match expected size")
unpacked.crc32 = crc32
if include_comp:
unpacked.comp_chunks = comp_chunks
return unused
def iter_sha1(iter):
"""Return the hexdigest of the SHA1 over a set of names.
Args:
iter: Iterator over string objects
Returns: 40-byte hex sha1 digest
"""
sha = sha1()
for name in iter:
sha.update(name)
return sha.hexdigest().encode("ascii")
def load_pack_index(path):
"""Load an index file by path.
Args:
path: Path to the index file
Returns: A PackIndex loaded from the given path
"""
with GitFile(path, "rb") as f:
return load_pack_index_file(path, f)
def _load_file_contents(f, size=None):
try:
fd = f.fileno()
except (UnsupportedOperation, AttributeError):
fd = None
# Attempt to use mmap if possible
if fd is not None:
if size is None:
size = os.fstat(fd).st_size
if has_mmap:
try:
contents = mmap.mmap(fd, size, access=mmap.ACCESS_READ)
except OSError:
# Perhaps a socket?
pass
else:
return contents, size
contents = f.read()
size = len(contents)
return contents, size
def load_pack_index_file(path, f):
"""Load an index file from a file-like object.
Args:
path: Path for the index file
f: File-like object
Returns: A PackIndex loaded from the given file
"""
contents, size = _load_file_contents(f)
if contents[:4] == b"\377tOc":
version = struct.unpack(b">L", contents[4:8])[0]
if version == 2:
return PackIndex2(path, file=f, contents=contents, size=size)
else:
raise KeyError("Unknown pack index format %d" % version)
else:
return PackIndex1(path, file=f, contents=contents, size=size)
def bisect_find_sha(start, end, sha, unpack_name):
"""Find a SHA in a data blob with sorted SHAs.
Args:
start: Start index of range to search
end: End index of range to search
sha: Sha to find
unpack_name: Callback to retrieve SHA by index
Returns: Index of the SHA, or None if it wasn't found
"""
assert start <= end
while start <= end:
i = (start + end) // 2
file_sha = unpack_name(i)
if file_sha < sha:
start = i + 1
elif file_sha > sha:
end = i - 1
else:
return i
return None
PackIndexEntry = Tuple[bytes, int, Optional[int]]
class PackIndex:
"""An index in to a packfile.
Given a sha id of an object a pack index can tell you the location in the
packfile of that object if it has it.
"""
def __eq__(self, other):
if not isinstance(other, PackIndex):
return False
for (name1, _, _), (name2, _, _) in zip(
self.iterentries(), other.iterentries()
):
if name1 != name2:
return False
return True
def __ne__(self, other):
return not self.__eq__(other)
def __len__(self) -> int:
"""Return the number of entries in this pack index."""
raise NotImplementedError(self.__len__)
def __iter__(self) -> Iterator[bytes]:
"""Iterate over the SHAs in this pack."""
return map(sha_to_hex, self._itersha())
def iterentries(self) -> Iterator[PackIndexEntry]:
"""Iterate over the entries in this pack index.
Returns: iterator over tuples with object name, offset in packfile and
crc32 checksum.
"""
raise NotImplementedError(self.iterentries)
def get_pack_checksum(self) -> bytes:
"""Return the SHA1 checksum stored for the corresponding packfile.
Returns: 20-byte binary digest
"""
raise NotImplementedError(self.get_pack_checksum)
def object_index(self, sha: bytes) -> int:
"""Return the index in to the corresponding packfile for the object.
Given the name of an object it will return the offset that object
lives at within the corresponding pack file. If the pack file doesn't
have the object then None will be returned.
"""
raise NotImplementedError(self.object_index)
def object_sha1(self, index: int) -> bytes:
"""Return the SHA1 corresponding to the index in the pack file."""
# PERFORMANCE/TODO(jelmer): Avoid scanning entire index
for (name, offset, crc32) in self.iterentries():
if offset == index:
return name
else:
raise KeyError(index)
def _object_index(self, sha: bytes) -> int:
"""See object_index.
Args:
sha: A *binary* SHA string. (20 characters long)_
"""
raise NotImplementedError(self._object_index)
def objects_sha1(self) -> bytes:
"""Return the hex SHA1 over all the shas of all objects in this pack.
Note: This is used for the filename of the pack.
"""
return iter_sha1(self._itersha())
def _itersha(self) -> Iterator[bytes]:
"""Yield all the SHA1's of the objects in the index, sorted."""
raise NotImplementedError(self._itersha)
def close(self):
pass
def check(self) -> None:
pass
class MemoryPackIndex(PackIndex):
"""Pack index that is stored entirely in memory."""
def __init__(self, entries, pack_checksum=None):
"""Create a new MemoryPackIndex.
Args:
entries: Sequence of name, idx, crc32 (sorted)
pack_checksum: Optional pack checksum
"""
self._by_sha = {}
self._by_index = {}
for name, idx, crc32 in entries:
self._by_sha[name] = idx
self._by_index[idx] = name
self._entries = entries
self._pack_checksum = pack_checksum
def get_pack_checksum(self):
return self._pack_checksum
def __len__(self):
return len(self._entries)
def object_index(self, sha):
if len(sha) == 40:
sha = hex_to_sha(sha)
return self._by_sha[sha][0]
def object_sha1(self, index):
return self._by_index[index]
def _itersha(self):
return iter(self._by_sha)
def iterentries(self):
return iter(self._entries)
class FilePackIndex(PackIndex):
"""Pack index that is based on a file.
To do the loop it opens the file, and indexes first 256 4 byte groups
with the first byte of the sha id. The value in the four byte group indexed
is the end of the group that shares the same starting byte. Subtract one
from the starting byte and index again to find the start of the group.
The values are sorted by sha id within the group, so do the math to find
the start and end offset and then bisect in to find if the value is
present.
"""
_fan_out_table: List[int]
def __init__(self, filename, file=None, contents=None, size=None):
"""Create a pack index object.
Provide it with the name of the index file to consider, and it will map
it whenever required.
"""
self._filename = filename
# Take the size now, so it can be checked each time we map the file to
# ensure that it hasn't changed.
if file is None:
self._file = GitFile(filename, "rb")
else:
self._file = file
if contents is None:
self._contents, self._size = _load_file_contents(self._file, size)
else:
self._contents, self._size = (contents, size)
@property
def path(self) -> str:
return self._filename
def __eq__(self, other):
# Quick optimization:
if (
isinstance(other, FilePackIndex)
and self._fan_out_table != other._fan_out_table
):
return False
return super().__eq__(other)
def close(self) -> None:
self._file.close()
if getattr(self._contents, "close", None) is not None:
self._contents.close()
def __len__(self) -> int:
"""Return the number of entries in this pack index."""
return self._fan_out_table[-1]
def _unpack_entry(self, i: int) -> PackIndexEntry:
"""Unpack the i-th entry in the index file.
Returns: Tuple with object name (SHA), offset in pack file and CRC32
checksum (if known).
"""
raise NotImplementedError(self._unpack_entry)
def _unpack_name(self, i):
"""Unpack the i-th name from the index file."""
raise NotImplementedError(self._unpack_name)
def _unpack_offset(self, i):
"""Unpack the i-th object offset from the index file."""
raise NotImplementedError(self._unpack_offset)
def _unpack_crc32_checksum(self, i):
"""Unpack the crc32 checksum for the ith object from the index file."""
raise NotImplementedError(self._unpack_crc32_checksum)
def _itersha(self) -> Iterator[bytes]:
for i in range(len(self)):
yield self._unpack_name(i)
def iterentries(self) -> Iterator[PackIndexEntry]:
"""Iterate over the entries in this pack index.
Returns: iterator over tuples with object name, offset in packfile and
crc32 checksum.
"""
for i in range(len(self)):
yield self._unpack_entry(i)
def _read_fan_out_table(self, start_offset: int):
ret = []
for i in range(0x100):
fanout_entry = self._contents[
start_offset + i * 4 : start_offset + (i + 1) * 4
]
ret.append(struct.unpack(">L", fanout_entry)[0])
return ret
def check(self) -> None:
"""Check that the stored checksum matches the actual checksum."""
actual = self.calculate_checksum()
stored = self.get_stored_checksum()
if actual != stored:
raise ChecksumMismatch(stored, actual)
def calculate_checksum(self) -> bytes:
"""Calculate the SHA1 checksum over this pack index.
Returns: This is a 20-byte binary digest
"""
return sha1(self._contents[:-20]).digest()
def get_pack_checksum(self) -> bytes:
"""Return the SHA1 checksum stored for the corresponding packfile.
Returns: 20-byte binary digest
"""
return bytes(self._contents[-40:-20])
def get_stored_checksum(self) -> bytes:
"""Return the SHA1 checksum stored for this index.
Returns: 20-byte binary digest
"""
return bytes(self._contents[-20:])
def object_index(self, sha: bytes) -> int:
"""Return the index in to the corresponding packfile for the object.
Given the name of an object it will return the offset that object
lives at within the corresponding pack file. If the pack file doesn't
have the object then None will be returned.
"""
if len(sha) == 40:
sha = hex_to_sha(sha)
try:
return self._object_index(sha)
except ValueError as exc:
closed = getattr(self._contents, "closed", None)
if closed in (None, True):
raise PackFileDisappeared(self) from exc
raise
def _object_index(self, sha: bytes) -> int:
"""See object_index.
Args:
sha: A *binary* SHA string. (20 characters long)_
"""
assert len(sha) == 20
idx = ord(sha[:1])
if idx == 0:
start = 0
else:
start = self._fan_out_table[idx - 1]
end = self._fan_out_table[idx]
i = bisect_find_sha(start, end, sha, self._unpack_name)
if i is None:
raise KeyError(sha)
return self._unpack_offset(i)
class PackIndex1(FilePackIndex):
"""Version 1 Pack Index file."""
def __init__(self, filename: str, file=None, contents=None, size=None):
super().__init__(filename, file, contents, size)
self.version = 1
self._fan_out_table = self._read_fan_out_table(0)
def _unpack_entry(self, i):
(offset, name) = unpack_from(">L20s", self._contents, (0x100 * 4) + (i * 24))
return (name, offset, None)
def _unpack_name(self, i):
offset = (0x100 * 4) + (i * 24) + 4
return self._contents[offset : offset + 20]
def _unpack_offset(self, i):
offset = (0x100 * 4) + (i * 24)
return unpack_from(">L", self._contents, offset)[0]
def _unpack_crc32_checksum(self, i):
# Not stored in v1 index files
return None
class PackIndex2(FilePackIndex):
"""Version 2 Pack Index file."""
def __init__(self, filename: str, file=None, contents=None, size=None):
super().__init__(filename, file, contents, size)
if self._contents[:4] != b"\377tOc":
raise AssertionError("Not a v2 pack index file")
(self.version,) = unpack_from(b">L", self._contents, 4)
if self.version != 2:
raise AssertionError("Version was %d" % self.version)
self._fan_out_table = self._read_fan_out_table(8)
self._name_table_offset = 8 + 0x100 * 4
self._crc32_table_offset = self._name_table_offset + 20 * len(self)
self._pack_offset_table_offset = self._crc32_table_offset + 4 * len(self)
self._pack_offset_largetable_offset = self._pack_offset_table_offset + 4 * len(
self
)
def _unpack_entry(self, i):
return (
self._unpack_name(i),
self._unpack_offset(i),
self._unpack_crc32_checksum(i),
)
def _unpack_name(self, i):
offset = self._name_table_offset + i * 20
return self._contents[offset : offset + 20]
def _unpack_offset(self, i):
offset = self._pack_offset_table_offset + i * 4
offset = unpack_from(">L", self._contents, offset)[0]
if offset & (2 ** 31):
offset = self._pack_offset_largetable_offset + (offset & (2 ** 31 - 1)) * 8
offset = unpack_from(">Q", self._contents, offset)[0]
return offset
def _unpack_crc32_checksum(self, i):
return unpack_from(">L", self._contents, self._crc32_table_offset + i * 4)[0]
def read_pack_header(read) -> Tuple[Optional[int], Optional[int]]:
"""Read the header of a pack file.
Args:
read: Read function
Returns: Tuple of (pack version, number of objects). If no data is
available to read, returns (None, None).
"""
header = read(12)
if not header:
return None, None
if header[:4] != b"PACK":
raise AssertionError("Invalid pack header %r" % header)
(version,) = unpack_from(b">L", header, 4)
if version not in (2, 3):
raise AssertionError("Version was %d" % version)
(num_objects,) = unpack_from(b">L", header, 8)
return (version, num_objects)
def chunks_length(chunks: Union[bytes, Iterable[bytes]]) -> int:
if isinstance(chunks, bytes):
return len(chunks)
else:
return sum(map(len, chunks))
def unpack_object(
read_all: Callable[[int], bytes],
read_some: Optional[Callable[[int], bytes]] = None,
compute_crc32=False,
include_comp=False,
zlib_bufsize=_ZLIB_BUFSIZE,
) -> Tuple[UnpackedObject, bytes]:
"""Unpack a Git object.
Args:
read_all: Read function that blocks until the number of requested
bytes are read.
read_some: Read function that returns at least one byte, but may not
return the number of bytes requested.
compute_crc32: If True, compute the CRC32 of the compressed data. If
False, the returned CRC32 will be None.
include_comp: If True, include compressed data in the result.
zlib_bufsize: An optional buffer size for zlib operations.
Returns: A tuple of (unpacked, unused), where unused is the unused data
leftover from decompression, and unpacked in an UnpackedObject with
the following attrs set:
* obj_chunks (for non-delta types)
* pack_type_num
* delta_base (for delta types)
* comp_chunks (if include_comp is True)
* decomp_chunks
* decomp_len
* crc32 (if compute_crc32 is True)
"""
if read_some is None:
read_some = read_all
if compute_crc32:
crc32 = 0
else:
crc32 = None
raw, crc32 = take_msb_bytes(read_all, crc32=crc32)
type_num = (raw[0] >> 4) & 0x07
size = raw[0] & 0x0F
for i, byte in enumerate(raw[1:]):
size += (byte & 0x7F) << ((i * 7) + 4)
delta_base: Union[int, bytes, None]
raw_base = len(raw)
if type_num == OFS_DELTA:
raw, crc32 = take_msb_bytes(read_all, crc32=crc32)
raw_base += len(raw)
if raw[-1] & 0x80:
raise AssertionError
delta_base_offset = raw[0] & 0x7F
for byte in raw[1:]:
delta_base_offset += 1
delta_base_offset <<= 7
delta_base_offset += byte & 0x7F
delta_base = delta_base_offset
elif type_num == REF_DELTA:
delta_base_obj = read_all(20)
if crc32 is not None:
crc32 = binascii.crc32(delta_base_obj, crc32)
delta_base = delta_base_obj
raw_base += 20
else:
delta_base = None
unpacked = UnpackedObject(type_num, delta_base, size, crc32)
unused = read_zlib_chunks(
read_some,
unpacked,
buffer_size=zlib_bufsize,
include_comp=include_comp,
)
return unpacked, unused
def _compute_object_size(value):
"""Compute the size of a unresolved object for use with LRUSizeCache."""
(num, obj) = value
if num in DELTA_TYPES:
return chunks_length(obj[1])
return chunks_length(obj)
class PackStreamReader:
"""Class to read a pack stream.
The pack is read from a ReceivableProtocol using read() or recv() as
appropriate.
"""
def __init__(self, read_all, read_some=None, zlib_bufsize=_ZLIB_BUFSIZE) -> None:
self.read_all = read_all
if read_some is None:
self.read_some = read_all
else:
self.read_some = read_some
self.sha = sha1()
self._offset = 0
self._rbuf = BytesIO()
# trailer is a deque to avoid memory allocation on small reads
self._trailer: Deque[bytes] = deque()
self._zlib_bufsize = zlib_bufsize
def _read(self, read, size):
"""Read up to size bytes using the given callback.
As a side effect, update the verifier's hash (excluding the last 20
bytes read).
Args:
read: The read callback to read from.
size: The maximum number of bytes to read; the particular
behavior is callback-specific.
"""
data = read(size)
# maintain a trailer of the last 20 bytes we've read
n = len(data)
self._offset += n
tn = len(self._trailer)
if n >= 20:
to_pop = tn
to_add = 20
else:
to_pop = max(n + tn - 20, 0)
to_add = n
self.sha.update(
bytes(bytearray([self._trailer.popleft() for _ in range(to_pop)]))
)
self._trailer.extend(data[-to_add:])
# hash everything but the trailer
self.sha.update(data[:-to_add])
return data
def _buf_len(self):
buf = self._rbuf
start = buf.tell()
buf.seek(0, SEEK_END)
end = buf.tell()
buf.seek(start)
return end - start
@property
def offset(self):
return self._offset - self._buf_len()
def read(self, size):
"""Read, blocking until size bytes are read."""
buf_len = self._buf_len()
if buf_len >= size:
return self._rbuf.read(size)
buf_data = self._rbuf.read()
self._rbuf = BytesIO()
return buf_data + self._read(self.read_all, size - buf_len)
def recv(self, size):
"""Read up to size bytes, blocking until one byte is read."""
buf_len = self._buf_len()
if buf_len:
data = self._rbuf.read(size)
if size >= buf_len:
self._rbuf = BytesIO()
return data
return self._read(self.read_some, size)
def __len__(self):
return self._num_objects
def read_objects(self, compute_crc32=False):
"""Read the objects in this pack file.
Args:
compute_crc32: If True, compute the CRC32 of the compressed
data. If False, the returned CRC32 will be None.
Returns: Iterator over UnpackedObjects with the following members set:
offset
obj_type_num
obj_chunks (for non-delta types)
delta_base (for delta types)
decomp_chunks
decomp_len
crc32 (if compute_crc32 is True)
Raises:
ChecksumMismatch: if the checksum of the pack contents does not
match the checksum in the pack trailer.
zlib.error: if an error occurred during zlib decompression.
IOError: if an error occurred writing to the output file.
"""
pack_version, self._num_objects = read_pack_header(self.read)
if pack_version is None:
return
for i in range(self._num_objects):
offset = self.offset
unpacked, unused = unpack_object(
self.read,
read_some=self.recv,
compute_crc32=compute_crc32,
zlib_bufsize=self._zlib_bufsize,
)
unpacked.offset = offset
# prepend any unused data to current read buffer
buf = BytesIO()
buf.write(unused)
buf.write(self._rbuf.read())
buf.seek(0)
self._rbuf = buf
yield unpacked
if self._buf_len() < 20:
# If the read buffer is full, then the last read() got the whole
# trailer off the wire. If not, it means there is still some of the
# trailer to read. We need to read() all 20 bytes; N come from the
# read buffer and (20 - N) come from the wire.
self.read(20)
pack_sha = bytearray(self._trailer)
if pack_sha != self.sha.digest():
raise ChecksumMismatch(sha_to_hex(pack_sha), self.sha.hexdigest())
class PackStreamCopier(PackStreamReader):
"""Class to verify a pack stream as it is being read.
The pack is read from a ReceivableProtocol using read() or recv() as
appropriate and written out to the given file-like object.
"""
def __init__(self, read_all, read_some, outfile, delta_iter=None):
"""Initialize the copier.
Args:
read_all: Read function that blocks until the number of
requested bytes are read.
read_some: Read function that returns at least one byte, but may
not return the number of bytes requested.
outfile: File-like object to write output through.
delta_iter: Optional DeltaChainIterator to record deltas as we
read them.
"""
super().__init__(read_all, read_some=read_some)
self.outfile = outfile
self._delta_iter = delta_iter
def _read(self, read, size):
"""Read data from the read callback and write it to the file."""
data = super()._read(read, size)
self.outfile.write(data)
return data
def verify(self):
"""Verify a pack stream and write it to the output file.
See PackStreamReader.iterobjects for a list of exceptions this may
throw.
"""
if self._delta_iter:
for unpacked in self.read_objects():
self._delta_iter.record(unpacked)
else:
for _ in self.read_objects():
pass
def obj_sha(type, chunks):
"""Compute the SHA for a numeric type and object chunks."""
sha = sha1()
sha.update(object_header(type, chunks_length(chunks)))
if isinstance(chunks, bytes):
sha.update(chunks)
else:
for chunk in chunks:
sha.update(chunk)
return sha.digest()
def compute_file_sha(f, start_ofs=0, end_ofs=0, buffer_size=1 << 16):
"""Hash a portion of a file into a new SHA.
Args:
f: A file-like object to read from that supports seek().
start_ofs: The offset in the file to start reading at.
end_ofs: The offset in the file to end reading at, relative to the
end of the file.
buffer_size: A buffer size for reading.
Returns: A new SHA object updated with data read from the file.
"""
sha = sha1()
f.seek(0, SEEK_END)
length = f.tell()
if (end_ofs < 0 and length + end_ofs < start_ofs) or end_ofs > length:
raise AssertionError(
"Attempt to read beyond file length. "
"start_ofs: %d, end_ofs: %d, file length: %d" % (start_ofs, end_ofs, length)
)
todo = length + end_ofs - start_ofs
f.seek(start_ofs)
while todo:
data = f.read(min(todo, buffer_size))
sha.update(data)
todo -= len(data)
return sha
class PackData:
"""The data contained in a packfile.
Pack files can be accessed both sequentially for exploding a pack, and
directly with the help of an index to retrieve a specific object.
The objects within are either complete or a delta against another.
The header is variable length. If the MSB of each byte is set then it
indicates that the subsequent byte is still part of the header.
For the first byte the next MS bits are the type, which tells you the type
of object, and whether it is a delta. The LS byte is the lowest bits of the
size. For each subsequent byte the LS 7 bits are the next MS bits of the
size, i.e. the last byte of the header contains the MS bits of the size.
For the complete objects the data is stored as zlib deflated data.
The size in the header is the uncompressed object size, so to uncompress
you need to just keep feeding data to zlib until you get an object back,
or it errors on bad data. This is done here by just giving the complete
buffer from the start of the deflated object on. This is bad, but until I
get mmap sorted out it will have to do.
Currently there are no integrity checks done. Also no attempt is made to
try and detect the delta case, or a request for an object at the wrong
position. It will all just throw a zlib or KeyError.
"""
def __init__(self, filename, file=None, size=None):
"""Create a PackData object representing the pack in the given filename.
The file must exist and stay readable until the object is disposed of.
It must also stay the same size. It will be mapped whenever needed.
Currently there is a restriction on the size of the pack as the python
mmap implementation is flawed.
"""
self._filename = filename
self._size = size
self._header_size = 12
if file is None:
self._file = GitFile(self._filename, "rb")
else:
self._file = file
(version, self._num_objects) = read_pack_header(self._file.read)
self._offset_cache = LRUSizeCache(
1024 * 1024 * 20, compute_size=_compute_object_size
)
@property
def filename(self):
return os.path.basename(self._filename)
@property
def path(self):
return self._filename
@classmethod
def from_file(cls, file, size=None):
return cls(str(file), file=file, size=size)
@classmethod
def from_path(cls, path):
return cls(filename=path)
def close(self):
self._file.close()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self.close()
def __eq__(self, other):
if isinstance(other, PackData):
return self.get_stored_checksum() == other.get_stored_checksum()
if isinstance(other, list):
if len(self) != len(other):
return False
for o1, o2 in zip(self.iterobjects(), other):
if o1 != o2:
return False
return True
return False
def _get_size(self):
if self._size is not None:
return self._size
self._size = os.path.getsize(self._filename)
if self._size < self._header_size:
errmsg = "%s is too small for a packfile (%d < %d)" % (
self._filename,
self._size,
self._header_size,
)
raise AssertionError(errmsg)
return self._size
def __len__(self):
"""Returns the number of objects in this pack."""
return self._num_objects
def calculate_checksum(self):
"""Calculate the checksum for this pack.
Returns: 20-byte binary SHA1 digest
"""
return compute_file_sha(self._file, end_ofs=-20).digest()
def iterobjects(self, progress: Optional[ProgressFn] = None, compute_crc32: bool = True):
self._file.seek(self._header_size)
for i in range(1, self._num_objects + 1):
offset = self._file.tell()
unpacked, unused = unpack_object(
self._file.read, compute_crc32=compute_crc32
)
if progress is not None:
progress(i, self._num_objects)
yield (
offset,
unpacked.pack_type_num,
unpacked._obj(),
unpacked.crc32,
)
# Back up over unused data.
self._file.seek(-len(unused), SEEK_CUR)
def _iter_unpacked(self):
# TODO(dborowitz): Merge this with iterobjects, if we can change its
# return type.
self._file.seek(self._header_size)
if self._num_objects is None:
return
for _ in range(self._num_objects):
offset = self._file.tell()
unpacked, unused = unpack_object(self._file.read, compute_crc32=False)
unpacked.offset = offset
yield unpacked
# Back up over unused data.
self._file.seek(-len(unused), SEEK_CUR)
def iterentries(self, progress: Optional[ProgressFn] = None, resolve_ext_ref: Optional[ResolveExtRefFn] = None):
"""Yield entries summarizing the contents of this pack.
Args:
progress: Progress function, called with current and total
object count.
Returns: iterator of tuples with (sha, offset, crc32)
"""
num_objects = self._num_objects
indexer = PackIndexer.for_pack_data(self, resolve_ext_ref=resolve_ext_ref)
for i, result in enumerate(indexer):
if progress is not None:
progress(i, num_objects)
yield result
def sorted_entries(self, progress: Optional[ProgressFn] = None, resolve_ext_ref: Optional[ResolveExtRefFn] = None):
"""Return entries in this pack, sorted by SHA.
Args:
progress: Progress function, called with current and total
object count
Returns: Iterator of tuples with (sha, offset, crc32)
"""
return sorted(self.iterentries(
progress=progress, resolve_ext_ref=resolve_ext_ref))
def create_index_v1(self, filename, progress=None, resolve_ext_ref=None):
"""Create a version 1 file for this data file.
Args:
filename: Index filename.
progress: Progress report function
Returns: Checksum of index file
"""
entries = self.sorted_entries(
progress=progress, resolve_ext_ref=resolve_ext_ref)
with GitFile(filename, "wb") as f:
return write_pack_index_v1(f, entries, self.calculate_checksum())
def create_index_v2(self, filename, progress=None, resolve_ext_ref=None):
"""Create a version 2 index file for this data file.
Args:
filename: Index filename.
progress: Progress report function
Returns: Checksum of index file
"""
entries = self.sorted_entries(
progress=progress, resolve_ext_ref=resolve_ext_ref)
with GitFile(filename, "wb") as f:
return write_pack_index_v2(f, entries, self.calculate_checksum())
def create_index(self, filename, progress=None, version=2, resolve_ext_ref=None):
"""Create an index file for this data file.
Args:
filename: Index filename.
progress: Progress report function
Returns: Checksum of index file
"""
if version == 1:
return self.create_index_v1(
filename, progress, resolve_ext_ref=resolve_ext_ref)
elif version == 2:
return self.create_index_v2(
filename, progress, resolve_ext_ref=resolve_ext_ref)
else:
raise ValueError("unknown index format %d" % version)
def get_stored_checksum(self):
"""Return the expected checksum stored in this pack."""
self._file.seek(-20, SEEK_END)
return self._file.read(20)
def check(self):
"""Check the consistency of this pack."""
actual = self.calculate_checksum()
stored = self.get_stored_checksum()
if actual != stored:
raise ChecksumMismatch(stored, actual)
def get_unpacked_object_at(self, offset: int, *, include_comp: bool = False) -> UnpackedObject:
"""Given offset in the packfile return a UnpackedObject.
"""
assert offset >= self._header_size
self._file.seek(offset)
unpacked, _ = unpack_object(self._file.read, include_comp=include_comp)
return unpacked
def get_compressed_data_at(self, offset):
"""Given offset in the packfile return compressed data that is there.
Using the associated index the location of an object can be looked up,
and then the packfile can be asked directly for that object using this
function.
"""
unpacked = self.get_unpacked_object_at(offset, include_comp=True)
return (
unpacked.pack_type_num,
unpacked.delta_base,
unpacked.comp_chunks,
)
def get_decompressed_data_at(self, offset: int) -> Tuple[int, Optional[bytes], List[bytes]]:
"""Given an offset in the packfile, decompress the data that is there.
Using the associated index the location of an object can be looked up,
and then the packfile can be asked directly for that object using this
function.
"""
unpacked = self.get_unpacked_object_at(offset, include_comp=False)
return (
unpacked.pack_type_num,
unpacked.delta_base,
unpacked.decomp_chunks,
)
def get_object_at(self, offset: int) -> Tuple[int, OldUnpackedObject]:
"""Given an offset in to the packfile return the object that is there.
Using the associated index the location of an object can be looked up,
and then the packfile can be asked directly for that object using this
function.
"""
try:
return self._offset_cache[offset]
except KeyError:
pass
unpacked = self.get_unpacked_object_at(offset, include_comp=False)
return (unpacked.pack_type_num, unpacked._obj())
class DeltaChainIterator:
"""Abstract iterator over pack data based on delta chains.
Each object in the pack is guaranteed to be inflated exactly once,
regardless of how many objects reference it as a delta base. As a result,
memory usage is proportional to the length of the longest delta chain.
Subclasses can override _result to define the result type of the iterator.
By default, results are UnpackedObjects with the following members set:
* offset
* obj_type_num
* obj_chunks
* pack_type_num
* delta_base (for delta types)
* comp_chunks (if _include_comp is True)
* decomp_chunks
* decomp_len
* crc32 (if _compute_crc32 is True)
"""
_compute_crc32 = False
_include_comp = False
def __init__(self, file_obj, *, resolve_ext_ref=None) -> None:
self._file = file_obj
self._resolve_ext_ref = resolve_ext_ref
self._pending_ofs: Dict[int, List[int]] = defaultdict(list)
self._pending_ref: Dict[bytes, List[int]] = defaultdict(list)
self._full_ofs: List[Tuple[int, int]] = []
self._ext_refs: List[bytes] = []
@classmethod
def for_pack_data(cls, pack_data: PackData, resolve_ext_ref=None):
walker = cls(None, resolve_ext_ref=resolve_ext_ref)
walker.set_pack_data(pack_data)
for unpacked in pack_data._iter_unpacked():
walker.record(unpacked)
return walker
def record(self, unpacked: UnpackedObject) -> None:
type_num = unpacked.pack_type_num
offset = unpacked.offset
if type_num == OFS_DELTA:
base_offset = offset - unpacked.delta_base
self._pending_ofs[base_offset].append(offset)
elif type_num == REF_DELTA:
self._pending_ref[unpacked.delta_base].append(offset)
else:
self._full_ofs.append((offset, type_num))
def set_pack_data(self, pack_data: PackData) -> None:
self._file = pack_data._file
def _walk_all_chains(self):
for offset, type_num in self._full_ofs:
yield from self._follow_chain(offset, type_num, None)
yield from self._walk_ref_chains()
assert not self._pending_ofs
def _ensure_no_pending(self) -> None:
if self._pending_ref:
raise KeyError([sha_to_hex(s) for s in self._pending_ref])
def _walk_ref_chains(self):
if not self._resolve_ext_ref:
self._ensure_no_pending()
return
for base_sha, pending in sorted(self._pending_ref.items()):
if base_sha not in self._pending_ref:
continue
try:
type_num, chunks = self._resolve_ext_ref(base_sha)
except KeyError:
# Not an external ref, but may depend on one. Either it will
# get popped via a _follow_chain call, or we will raise an
# error below.
continue
self._ext_refs.append(base_sha)
self._pending_ref.pop(base_sha)
for new_offset in pending:
yield from self._follow_chain(new_offset, type_num, chunks)
self._ensure_no_pending()
def _result(self, unpacked):
return unpacked
def _resolve_object(self, offset: int, obj_type_num: int, base_chunks: List[bytes]) -> UnpackedObject:
self._file.seek(offset)
unpacked, _ = unpack_object(
self._file.read,
include_comp=self._include_comp,
compute_crc32=self._compute_crc32,
)
unpacked.offset = offset
if base_chunks is None:
assert unpacked.pack_type_num == obj_type_num
else:
assert unpacked.pack_type_num in DELTA_TYPES
unpacked.obj_type_num = obj_type_num
unpacked.obj_chunks = apply_delta(base_chunks, unpacked.decomp_chunks)
return unpacked
def _follow_chain(self, offset: int, obj_type_num: int, base_chunks: List[bytes]):
# Unlike PackData.get_object_at, there is no need to cache offsets as
# this approach by design inflates each object exactly once.
todo = [(offset, obj_type_num, base_chunks)]
while todo:
(offset, obj_type_num, base_chunks) = todo.pop()
unpacked = self._resolve_object(offset, obj_type_num, base_chunks)
yield self._result(unpacked)
unblocked = chain(
self._pending_ofs.pop(unpacked.offset, []),
self._pending_ref.pop(unpacked.sha(), []),
)
todo.extend(
(new_offset, unpacked.obj_type_num, unpacked.obj_chunks) # type: ignore
for new_offset in unblocked
)
def __iter__(self):
return self._walk_all_chains()
def ext_refs(self):
return self._ext_refs
class PackIndexer(DeltaChainIterator):
"""Delta chain iterator that yields index entries."""
_compute_crc32 = True
def _result(self, unpacked):
return unpacked.sha(), unpacked.offset, unpacked.crc32
class PackInflater(DeltaChainIterator):
"""Delta chain iterator that yields ShaFile objects."""
def _result(self, unpacked):
return unpacked.sha_file()
class SHA1Reader:
"""Wrapper for file-like object that remembers the SHA1 of its data."""
def __init__(self, f):
self.f = f
self.sha1 = sha1(b"")
def read(self, num=None):
data = self.f.read(num)
self.sha1.update(data)
return data
def check_sha(self):
stored = self.f.read(20)
if stored != self.sha1.digest():
raise ChecksumMismatch(self.sha1.hexdigest(), sha_to_hex(stored))
def close(self):
return self.f.close()
def tell(self):
return self.f.tell()
class SHA1Writer:
"""Wrapper for file-like object that remembers the SHA1 of its data."""
def __init__(self, f):
self.f = f
self.length = 0
self.sha1 = sha1(b"")
def write(self, data):
self.sha1.update(data)
self.f.write(data)
self.length += len(data)
def write_sha(self):
sha = self.sha1.digest()
assert len(sha) == 20
self.f.write(sha)
self.length += len(sha)
return sha
def close(self):
sha = self.write_sha()
self.f.close()
return sha
def offset(self):
return self.length
def tell(self):
return self.f.tell()
def pack_object_header(type_num, delta_base, size):
"""Create a pack object header for the given object info.
Args:
type_num: Numeric type of the object.
delta_base: Delta base offset or ref, or None for whole objects.
size: Uncompressed object size.
Returns: A header for a packed object.
"""
header = []
c = (type_num << 4) | (size & 15)
size >>= 4
while size:
header.append(c | 0x80)
c = size & 0x7F
size >>= 7
header.append(c)
if type_num == OFS_DELTA:
ret = [delta_base & 0x7F]
delta_base >>= 7
while delta_base:
delta_base -= 1
ret.insert(0, 0x80 | (delta_base & 0x7F))
delta_base >>= 7
header.extend(ret)
elif type_num == REF_DELTA:
assert len(delta_base) == 20
header += delta_base
return bytearray(header)
def pack_object_chunks(type, object, compression_level=-1):
"""Generate chunks for a pack object.
Args:
type: Numeric type of the object
object: Object to write
compression_level: the zlib compression level
Returns: Chunks
"""
if type in DELTA_TYPES:
delta_base, object = object
else:
delta_base = None
if isinstance(object, bytes):
object = [object]
yield bytes(pack_object_header(type, delta_base, sum(map(len, object))))
compressor = zlib.compressobj(level=compression_level)
for data in object:
yield compressor.compress(data)
yield compressor.flush()
def write_pack_object(write, type, object, sha=None, compression_level=-1):
"""Write pack object to a file.
Args:
write: Write function to use
type: Numeric type of the object
object: Object to write
compression_level: the zlib compression level
Returns: Tuple with offset at which the object was written, and crc32
"""
if hasattr(write, 'write'):
warnings.warn(
'write_pack_object() now takes a write rather than file argument',
DeprecationWarning, stacklevel=2)
write = write.write
crc32 = 0
for chunk in pack_object_chunks(
type, object, compression_level=compression_level):
write(chunk)
if sha is not None:
sha.update(chunk)
crc32 = binascii.crc32(chunk, crc32)
return crc32 & 0xFFFFFFFF
def write_pack(
filename,
objects,
*,
deltify: Optional[bool] = None,
delta_window_size: Optional[int] = None,
compression_level: int = -1,
reuse_pack: Optional[PackedObjectContainer] = None):
"""Write a new pack data file.
Args:
filename: Path to the new pack file (without .pack extension)
objects: (object, path) tuple iterable to write. Should provide __len__
delta_window_size: Delta window size
deltify: Whether to deltify pack objects
compression_level: the zlib compression level
Returns: Tuple with checksum of pack file and index file
"""
with GitFile(filename + ".pack", "wb") as f:
entries, data_sum = write_pack_objects(
f.write,
objects,
delta_window_size=delta_window_size,
deltify=deltify,
compression_level=compression_level,
reuse_pack=reuse_pack,
)
entries = sorted([(k, v[0], v[1]) for (k, v) in entries.items()])
with GitFile(filename + ".idx", "wb") as f:
return data_sum, write_pack_index_v2(f, entries, data_sum)
def pack_header_chunks(num_objects):
"""Yield chunks for a pack header."""
yield b"PACK" # Pack header
yield struct.pack(b">L", 2) # Pack version
yield struct.pack(b">L", num_objects) # Number of objects in pack
def write_pack_header(write, num_objects):
"""Write a pack header for the given number of objects."""
if hasattr(write, 'write'):
write = write.write
warnings.warn(
'write_pack_header() now takes a write rather than file argument',
DeprecationWarning, stacklevel=2)
for chunk in pack_header_chunks(num_objects):
write(chunk)
def deltify_pack_objects(
objects: Iterable[Tuple[ShaFile, str]],
window_size: Optional[int] = None,
reuse_pack: Optional[PackedObjectContainer] = None):
"""Generate deltas for pack objects.
Args:
objects: An iterable of (object, path) tuples to deltify.
window_size: Window size; None for default
reuse_pack: Pack object we can search for objects to reuse
Returns: Iterator over type_num, object id, delta_base, content
delta_base is None for full text entries
"""
# TODO(jelmer): Use threads
if window_size is None:
window_size = DEFAULT_PACK_DELTA_WINDOW_SIZE
reused_deltas = set()
if reuse_pack:
# Build a set of SHA1 IDs which will be part of this pack file.
# We can only reuse a delta if its base will be present in the
# generated pack file.
objects_to_pack = set()
for obj, path in objects:
objects_to_pack.add(sha_to_hex(obj.sha().digest()))
for o, _ in objects:
sha_digest = o.sha().digest()
# get_raw_unresolved() translates OFS_DELTA into REF_DELTA for us
try:
(obj_type, delta_base, chunks) = reuse_pack.get_raw_unresolved(sha_digest)
except KeyError:
continue
if obj_type == REF_DELTA and delta_base in objects_to_pack:
yield obj_type, sha_digest, hex_to_sha(delta_base), chunks
reused_deltas.add(sha_digest)
# Build a list of objects ordered by the magic Linus heuristic
# This helps us find good objects to diff against us
magic = []
for obj, path in objects:
if obj.sha().digest() in reused_deltas:
continue
magic.append((obj.type_num, path, -obj.raw_length(), obj))
magic.sort()
possible_bases: Deque[Tuple[bytes, int, List[bytes]]] = deque()
for type_num, path, neg_length, o in magic:
raw = o.as_raw_chunks()
winner = raw
winner_len = sum(map(len, winner))
winner_base = None
for base_id, base_type_num, base in possible_bases:
if base_type_num != type_num:
continue
delta_len = 0
delta = []
for chunk in create_delta(base, raw):
delta_len += len(chunk)
if delta_len >= winner_len:
break
delta.append(chunk)
else:
winner_base = base_id
winner = delta
winner_len = sum(map(len, winner))
yield type_num, o.sha().digest(), winner_base, winner
possible_bases.appendleft((o.sha().digest(), type_num, raw))
while len(possible_bases) > window_size:
possible_bases.pop()
def pack_objects_to_data(
objects,
delta_window_size: Optional[int] = None,
deltify: Optional[bool] = None,
reuse_pack: Optional[PackedObjectContainer] = None):
"""Create pack data from objects
Args:
objects: Pack objects
Returns: Tuples with (type_num, hexdigest, delta base, object chunks)
"""
count = len(objects)
if deltify is None:
# PERFORMANCE/TODO(jelmer): This should be enabled but is *much* too
# slow at the moment.
deltify = False
if deltify:
pack_contents = deltify_pack_objects(
objects, window_size=delta_window_size, reuse_pack=reuse_pack)
return (count, pack_contents)
else:
return (
count,
(
(o.type_num, o.sha().digest(), None, o.as_raw_chunks())
for (o, path) in objects
),
)
def write_pack_objects(
write, objects,
delta_window_size: Optional[int] = None,
deltify: Optional[bool] = None,
reuse_pack: Optional[PackedObjectContainer] = None,
compression_level: int = -1
):
"""Write a new pack data file.
Args:
write: write function to use
objects: Iterable of (object, path) tuples to write. Should provide
__len__
delta_window_size: Sliding window size for searching for deltas;
Set to None for default window size.
deltify: Whether to deltify objects
reuse_pack: Pack object we can search for objects to reuse
compression_level: the zlib compression level to use
Returns: Dict mapping id -> (offset, crc32 checksum), pack checksum
"""
if hasattr(write, 'write'):
warnings.warn(
'write_pack_objects() now takes a write rather than file argument',
DeprecationWarning, stacklevel=2)
write = write.write
pack_contents_count, pack_contents = pack_objects_to_data(
objects, delta_window_size=delta_window_size,
deltify=deltify,
reuse_pack=reuse_pack)
return write_pack_data(
write,
pack_contents_count,
pack_contents,
compression_level=compression_level,
)
class PackChunkGenerator:
def __init__(self, num_records=None, records=None, progress=None, compression_level=-1):
self.cs = sha1(b"")
self.entries = {}
self._it = self._pack_data_chunks(
num_records=num_records, records=records, progress=progress, compression_level=compression_level)
def sha1digest(self):
return self.cs.digest()
def __iter__(self):
return self._it
def _pack_data_chunks(self, num_records=None, records=None, progress=None, compression_level=-1):
"""Iterate pack data file chunks..
Args:
num_records: Number of records (defaults to len(records) if None)
records: Iterator over type_num, object_id, delta_base, raw
progress: Function to report progress to
compression_level: the zlib compression level
Returns: Dict mapping id -> (offset, crc32 checksum), pack checksum
"""
# Write the pack
if num_records is None:
num_records = len(records)
offset = 0
for chunk in pack_header_chunks(num_records):
yield chunk
self.cs.update(chunk)
offset += len(chunk)
actual_num_records = 0
for i, (type_num, object_id, delta_base, raw) in enumerate(records):
if progress is not None:
progress(("writing pack data: %d/%d\r" % (i, num_records)).encode("ascii"))
if delta_base is not None:
try:
base_offset, base_crc32 = self.entries[delta_base]
except KeyError:
type_num = REF_DELTA
raw = (delta_base, raw)
else:
type_num = OFS_DELTA
raw = (offset - base_offset, raw)
crc32 = 0
object_size = 0
for chunk in pack_object_chunks(type_num, raw, compression_level=compression_level):
yield chunk
crc32 = binascii.crc32(chunk, crc32)
self.cs.update(chunk)
object_size += len(chunk)
actual_num_records += 1
self.entries[object_id] = (offset, crc32)
offset += object_size
if actual_num_records != num_records:
raise AssertionError(
'actual records written differs: %d != %d' % (
actual_num_records, num_records))
yield self.cs.digest()
def write_pack_data(write, num_records=None, records=None, progress=None, compression_level=-1):
"""Write a new pack data file.
Args:
write: Write function to use
num_records: Number of records (defaults to len(records) if None)
records: Iterator over type_num, object_id, delta_base, raw
progress: Function to report progress to
compression_level: the zlib compression level
Returns: Dict mapping id -> (offset, crc32 checksum), pack checksum
"""
if hasattr(write, 'write'):
warnings.warn(
'write_pack_data() now takes a write rather than file argument',
DeprecationWarning, stacklevel=2)
write = write.write
chunk_generator = PackChunkGenerator(
num_records=num_records, records=records, progress=progress,
compression_level=compression_level)
for chunk in chunk_generator:
write(chunk)
return chunk_generator.entries, chunk_generator.sha1digest()
def write_pack_index_v1(f, entries, pack_checksum):
"""Write a new pack index file.
Args:
f: A file-like object to write to
entries: List of tuples with object name (sha), offset_in_pack,
and crc32_checksum.
pack_checksum: Checksum of the pack file.
Returns: The SHA of the written index file
"""
f = SHA1Writer(f)
fan_out_table = defaultdict(lambda: 0)
for (name, offset, entry_checksum) in entries:
fan_out_table[ord(name[:1])] += 1
# Fan-out table
for i in range(0x100):
f.write(struct.pack(">L", fan_out_table[i]))
fan_out_table[i + 1] += fan_out_table[i]
for (name, offset, entry_checksum) in entries:
if not (offset <= 0xFFFFFFFF):
raise TypeError("pack format 1 only supports offsets < 2Gb")
f.write(struct.pack(">L20s", offset, name))
assert len(pack_checksum) == 20
f.write(pack_checksum)
return f.write_sha()
def _delta_encode_size(size) -> bytes:
ret = bytearray()
c = size & 0x7F
size >>= 7
while size:
ret.append(c | 0x80)
c = size & 0x7F
size >>= 7
ret.append(c)
return bytes(ret)
# The length of delta compression copy operations in version 2 packs is limited
# to 64K. To copy more, we use several copy operations. Version 3 packs allow
# 24-bit lengths in copy operations, but we always make version 2 packs.
_MAX_COPY_LEN = 0xFFFF
def _encode_copy_operation(start, length):
scratch = bytearray([0x80])
for i in range(4):
if start & 0xFF << i * 8:
scratch.append((start >> i * 8) & 0xFF)
scratch[0] |= 1 << i
for i in range(2):
if length & 0xFF << i * 8:
scratch.append((length >> i * 8) & 0xFF)
scratch[0] |= 1 << (4 + i)
return bytes(scratch)
def create_delta(base_buf, target_buf):
"""Use python difflib to work out how to transform base_buf to target_buf.
Args:
base_buf: Base buffer
target_buf: Target buffer
"""
if isinstance(base_buf, list):
base_buf = b''.join(base_buf)
if isinstance(target_buf, list):
target_buf = b''.join(target_buf)
assert isinstance(base_buf, bytes)
assert isinstance(target_buf, bytes)
# write delta header
yield _delta_encode_size(len(base_buf))
yield _delta_encode_size(len(target_buf))
# write out delta opcodes
seq = SequenceMatcher(isjunk=None, a=base_buf, b=target_buf)
for opcode, i1, i2, j1, j2 in seq.get_opcodes():
# Git patch opcodes don't care about deletes!
# if opcode == 'replace' or opcode == 'delete':
# pass
if opcode == "equal":
# If they are equal, unpacker will use data from base_buf
# Write out an opcode that says what range to use
copy_start = i1
copy_len = i2 - i1
while copy_len > 0:
to_copy = min(copy_len, _MAX_COPY_LEN)
yield _encode_copy_operation(copy_start, to_copy)
copy_start += to_copy
copy_len -= to_copy
if opcode == "replace" or opcode == "insert":
# If we are replacing a range or adding one, then we just
# output it to the stream (prefixed by its size)
s = j2 - j1
o = j1
while s > 127:
yield bytes([127])
yield memoryview(target_buf)[o:o + 127]
s -= 127
o += 127
yield bytes([s])
yield memoryview(target_buf)[o:o + s]
def apply_delta(src_buf, delta):
"""Based on the similar function in git's patch-delta.c.
Args:
src_buf: Source buffer
delta: Delta instructions
"""
if not isinstance(src_buf, bytes):
src_buf = b"".join(src_buf)
if not isinstance(delta, bytes):
delta = b"".join(delta)
out = []
index = 0
delta_length = len(delta)
def get_delta_header_size(delta, index):
size = 0
i = 0
while delta:
cmd = ord(delta[index : index + 1])
index += 1
size |= (cmd & ~0x80) << i
i += 7
if not cmd & 0x80:
break
return size, index
src_size, index = get_delta_header_size(delta, index)
dest_size, index = get_delta_header_size(delta, index)
assert src_size == len(src_buf), "%d vs %d" % (src_size, len(src_buf))
while index < delta_length:
cmd = ord(delta[index : index + 1])
index += 1
if cmd & 0x80:
cp_off = 0
for i in range(4):
if cmd & (1 << i):
x = ord(delta[index : index + 1])
index += 1
cp_off |= x << (i * 8)
cp_size = 0
# Version 3 packs can contain copy sizes larger than 64K.
for i in range(3):
if cmd & (1 << (4 + i)):
x = ord(delta[index : index + 1])
index += 1
cp_size |= x << (i * 8)
if cp_size == 0:
cp_size = 0x10000
if (
cp_off + cp_size < cp_size
or cp_off + cp_size > src_size
or cp_size > dest_size
):
break
out.append(src_buf[cp_off : cp_off + cp_size])
elif cmd != 0:
out.append(delta[index : index + cmd])
index += cmd
else:
raise ApplyDeltaError("Invalid opcode 0")
if index != delta_length:
raise ApplyDeltaError("delta not empty: %r" % delta[index:])
if dest_size != chunks_length(out):
raise ApplyDeltaError("dest size incorrect")
return out
def write_pack_index_v2(
f, entries: Iterable[PackIndexEntry], pack_checksum: bytes) -> bytes:
"""Write a new pack index file.
Args:
f: File-like object to write to
entries: List of tuples with object name (sha), offset_in_pack, and
crc32_checksum.
pack_checksum: Checksum of the pack file.
Returns: The SHA of the index file written
"""
f = SHA1Writer(f)
f.write(b"\377tOc") # Magic!
f.write(struct.pack(">L", 2))
fan_out_table: Dict[int, int] = defaultdict(lambda: 0)
for (name, offset, entry_checksum) in entries:
fan_out_table[ord(name[:1])] += 1
# Fan-out table
largetable: List[int] = []
for i in range(0x100):
f.write(struct.pack(b">L", fan_out_table[i]))
fan_out_table[i + 1] += fan_out_table[i]
for (name, offset, entry_checksum) in entries:
f.write(name)
for (name, offset, entry_checksum) in entries:
f.write(struct.pack(b">L", entry_checksum))
for (name, offset, entry_checksum) in entries:
if offset < 2 ** 31:
f.write(struct.pack(b">L", offset))
else:
f.write(struct.pack(b">L", 2 ** 31 + len(largetable)))
largetable.append(offset)
for offset in largetable:
f.write(struct.pack(b">Q", offset))
assert len(pack_checksum) == 20
f.write(pack_checksum)
return f.write_sha()
write_pack_index = write_pack_index_v2
class _PackTupleIterable:
"""Helper for Pack.pack_tuples."""
def __init__(self, iterobjects, length):
self._iterobjects = iterobjects
self._length = length
def __len__(self):
return self._length
def __iter__(self):
return ((o, None) for o in self._iterobjects())
class Pack:
"""A Git pack object."""
_data_load: Optional[Callable[[], PackData]]
_idx_load: Optional[Callable[[], PackIndex]]
_data: Optional[PackData]
_idx: Optional[PackIndex]
def __init__(self, basename, resolve_ext_ref: Optional[ResolveExtRefFn] = None):
self._basename = basename
self._data = None
self._idx = None
self._idx_path = self._basename + ".idx"
self._data_path = self._basename + ".pack"
self._data_load = lambda: PackData(self._data_path)
self._idx_load = lambda: load_pack_index(self._idx_path)
self.resolve_ext_ref = resolve_ext_ref
@classmethod
def from_lazy_objects(cls, data_fn, idx_fn):
"""Create a new pack object from callables to load pack data and
index objects."""
ret = cls("")
ret._data_load = data_fn
ret._idx_load = idx_fn
return ret
@classmethod
def from_objects(cls, data, idx):
"""Create a new pack object from pack data and index objects."""
ret = cls("")
ret._data = data
ret._data_load = None
ret._idx = idx
ret._idx_load = None
ret.check_length_and_checksum()
return ret
def name(self):
"""The SHA over the SHAs of the objects in this pack."""
return self.index.objects_sha1()
@property
def data(self) -> PackData:
"""The pack data object being used."""
if self._data is None:
assert self._data_load
self._data = self._data_load()
self.check_length_and_checksum()
return self._data
@property
def index(self) -> PackIndex:
"""The index being used.
Note: This may be an in-memory index
"""
if self._idx is None:
assert self._idx_load
self._idx = self._idx_load()
return self._idx
def close(self):
if self._data is not None:
self._data.close()
if self._idx is not None:
self._idx.close()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self.close()
def __eq__(self, other):
return isinstance(self, type(other)) and self.index == other.index
def __len__(self):
"""Number of entries in this pack."""
return len(self.index)
def __repr__(self):
return "{}({!r})".format(self.__class__.__name__, self._basename)
def __iter__(self):
"""Iterate over all the sha1s of the objects in this pack."""
return iter(self.index)
def check_length_and_checksum(self) -> None:
"""Sanity check the length and checksum of the pack index and data."""
assert len(self.index) == len(self.data)
idx_stored_checksum = self.index.get_pack_checksum()
data_stored_checksum = self.data.get_stored_checksum()
if idx_stored_checksum != data_stored_checksum:
raise ChecksumMismatch(
sha_to_hex(idx_stored_checksum),
sha_to_hex(data_stored_checksum),
)
def check(self) -> None:
"""Check the integrity of this pack.
Raises:
ChecksumMismatch: if a checksum for the index or data is wrong
"""
self.index.check()
self.data.check()
for obj in self.iterobjects():
obj.check()
# TODO: object connectivity checks
def get_stored_checksum(self) -> bytes:
return self.data.get_stored_checksum()
def __contains__(self, sha1: bytes) -> bool:
"""Check whether this pack contains a particular SHA1."""
try:
self.index.object_index(sha1)
return True
except KeyError:
return False
def get_raw_unresolved(self, sha1: bytes) -> Tuple[int, Optional[bytes], List[bytes]]:
"""Get raw unresolved data for a SHA.
Args:
sha1: SHA to return data for
Returns: Tuple with pack object type, delta base (if applicable),
list of data chunks
"""
offset = self.index.object_index(sha1)
(obj_type, delta_base, chunks) = self.data.get_compressed_data_at(offset)
if obj_type == OFS_DELTA:
delta_base = sha_to_hex(self.index.object_sha1(offset - delta_base))
obj_type = REF_DELTA
return (obj_type, delta_base, chunks)
def get_raw(self, sha1: bytes) -> Tuple[int, bytes]:
offset = self.index.object_index(sha1)
obj_type, obj = self.data.get_object_at(offset)
type_num, chunks = self.resolve_object(offset, obj_type, obj)
return type_num, b"".join(chunks)
def __getitem__(self, sha1: bytes) -> bytes:
"""Retrieve the specified SHA1."""
type, uncomp = self.get_raw(sha1)
return ShaFile.from_raw_string(type, uncomp, sha=sha1)
def iterobjects(self):
"""Iterate over the objects in this pack."""
return iter(
PackInflater.for_pack_data(self.data, resolve_ext_ref=self.resolve_ext_ref)
)
def pack_tuples(self):
"""Provide an iterable for use with write_pack_objects.
Returns: Object that can iterate over (object, path) tuples
and provides __len__
"""
return _PackTupleIterable(self.iterobjects, len(self))
def keep(self, msg: Optional[bytes] = None) -> str:
"""Add a .keep file for the pack, preventing git from garbage collecting it.
Args:
msg: A message written inside the .keep file; can be used later
to determine whether or not a .keep file is obsolete.
Returns: The path of the .keep file, as a string.
"""
keepfile_name = "%s.keep" % self._basename
with GitFile(keepfile_name, "wb") as keepfile:
if msg:
keepfile.write(msg)
keepfile.write(b"\n")
return keepfile_name
def get_ref(self, sha: bytes) -> Tuple[Optional[int], int, OldUnpackedObject]:
"""Get the object for a ref SHA, only looking in this pack."""
# TODO: cache these results
try:
offset = self.index.object_index(sha)
except KeyError:
offset = None
if offset:
type, obj = self.data.get_object_at(offset)
elif self.resolve_ext_ref:
type, obj = self.resolve_ext_ref(sha)
else:
raise KeyError(sha)
return offset, type, obj
def resolve_object(self, offset: int, type: int, obj, get_ref=None) -> Tuple[int, Iterable[bytes]]:
"""Resolve an object, possibly resolving deltas when necessary.
Returns: Tuple with object type and contents.
"""
# Walk down the delta chain, building a stack of deltas to reach
# the requested object.
base_offset = offset
base_type = type
base_obj = obj
delta_stack = []
while base_type in DELTA_TYPES:
prev_offset = base_offset
if get_ref is None:
get_ref = self.get_ref
if base_type == OFS_DELTA:
(delta_offset, delta) = base_obj
# TODO: clean up asserts and replace with nicer error messages
base_offset = base_offset - delta_offset
base_type, base_obj = self.data.get_object_at(base_offset)
assert isinstance(base_type, int)
elif base_type == REF_DELTA:
(basename, delta) = base_obj
assert isinstance(basename, bytes) and len(basename) == 20
base_offset, base_type, base_obj = get_ref(basename)
assert isinstance(base_type, int)
delta_stack.append((prev_offset, base_type, delta))
# Now grab the base object (mustn't be a delta) and apply the
# deltas all the way up the stack.
chunks = base_obj
for prev_offset, delta_type, delta in reversed(delta_stack):
chunks = apply_delta(chunks, delta)
# TODO(dborowitz): This can result in poor performance if
# large base objects are separated from deltas in the pack.
# We should reorganize so that we apply deltas to all
# objects in a chain one after the other to optimize cache
# performance.
if prev_offset is not None:
self.data._offset_cache[prev_offset] = base_type, chunks
return base_type, chunks
def entries(self, progress: Optional[ProgressFn] = None) -> Iterator[PackIndexEntry]:
"""Yield entries summarizing the contents of this pack.
Args:
progress: Progress function, called with current and total
object count.
Returns: iterator of tuples with (sha, offset, crc32)
"""
return self.data.iterentries(
progress=progress, resolve_ext_ref=self.resolve_ext_ref)
def sorted_entries(self, progress: Optional[ProgressFn] = None) -> Iterator[PackIndexEntry]:
"""Return entries in this pack, sorted by SHA.
Args:
progress: Progress function, called with current and total
object count
Returns: Iterator of tuples with (sha, offset, crc32)
"""
return self.data.sorted_entries(
progress=progress, resolve_ext_ref=self.resolve_ext_ref)
try:
from dulwich._pack import ( # type: ignore # noqa: F811
apply_delta,
bisect_find_sha,
)
except ImportError:
pass