def from_file(cls, filename):
"""Get the contents of a SHA file on disk"""
size = os.path.getsize(filename)
f = GitFile(filename, 'rb')
try:
map = mmap.mmap(f.fileno(), size, access=mmap.ACCESS_READ)
shafile = cls._parse_file(map)
return shafile
finally:
f.close()
class PackIndex(object):
"""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.
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.
"""
def __init__(self, filename, file=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
fileno = getattr(self._file, 'fileno', None)
if fileno is not None:
fd = self._file.fileno()
if size is None:
self._size = os.fstat(fd).st_size
else:
self._size = size
self._contents = mmap.mmap(fd, self._size,
access=mmap.ACCESS_READ)
else:
self._file.seek(0)
self._contents = self._file.read()
self._size = len(self._contents)
def __eq__(self, other):
if not isinstance(other, PackIndex):
return False
if self._fan_out_table != other._fan_out_table:
return False
for (name1, _, _), (name2, _, _) in izip(self.iterentries(), other.iterentries()):
if name1 != name2:
return False
return True
def __ne__(self, other):
return not self.__eq__(other)
def close(self):
self._file.close()
def __len__(self):
"""Return the number of entries in this pack index."""
return self._fan_out_table[-1]
def _unpack_entry(self, i):
"""Unpack the i-th entry in the index file.
:return: 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 i-th object from the index file."""
raise NotImplementedError(self._unpack_crc32_checksum)
def __iter__(self):
"""Iterate over the SHAs in this pack."""
return imap(sha_to_hex, self._itersha())
def _itersha(self):
for i in range(len(self)):
yield self._unpack_name(i)
def objects_sha1(self):
"""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 iterentries(self):
"""Iterate over the entries in this pack index.
Will yield 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):
ret = []
for i in range(0x100):
ret.append(struct.unpack(">L", self._contents[start_offset+i*4:start_offset+(i+1)*4])[0])
return ret
def check(self):
"""Check that the stored checksum matches the actual checksum."""
# TODO: Check pack contents, too
return self.calculate_checksum() == self.get_stored_checksum()
def calculate_checksum(self):
"""Calculate the SHA1 checksum over this pack index.
:return: This is a 20-byte binary digest
"""
return make_sha(self._contents[:-20]).digest()
def get_pack_checksum(self):
"""Return the SHA1 checksum stored for the corresponding packfile.
:return: 20-byte binary digest
"""
return str(self._contents[-40:-20])
def get_stored_checksum(self):
"""Return the SHA1 checksum stored for this index.
:return: 20-byte binary digest
"""
return str(self._contents[-20:])
def object_index(self, sha):
"""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)
return self._object_index(sha)
def _object_index(self, sha):
"""See object_index.
:param sha: A *binary* SHA string. (20 characters long)_
"""
assert len(sha) == 20
idx = ord(sha[0])
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)
