"""Contains PackIndexFile and PackFile implementations""" from gitdb.exc import ( BadObject, UnsupportedOperation ) from util import ( zlib, LazyMixin, unpack_from, file_contents_ro_filepath, ) from fun import ( pack_object_header_info, is_equal_canonical_sha, type_id_to_type_map, write_object, stream_copy, chunk_size, delta_types, OFS_DELTA, REF_DELTA, msb_size ) try: from _fun import PackIndexFile_sha_to_index except ImportError: pass # END try c module from base import ( # Amazing ! OInfo, OStream, OPackInfo, OPackStream, ODeltaPackInfo, ODeltaPackStream, ) from stream import ( DecompressMemMapReader, DeltaApplyReader, Sha1Writer, NullStream, ) from struct import ( pack, unpack, ) from itertools import izip import array import os __all__ = ('PackIndexFile', 'PackFile', 'PackEntity') #{ Utilities def pack_object_at(data, offset, as_stream): """ :return: Tuple(abs_data_offset, PackInfo|PackStream) an object of the correct type according to the type_id of the object. If as_stream is True, the object will contain a stream, allowing the data to be read decompressed. :param data: random accessable data containing all required information :parma offset: offset in to the data at which the object information is located :param as_stream: if True, a stream object will be returned that can read the data, otherwise you receive an info object only""" data = buffer(data, offset) type_id, uncomp_size, data_rela_offset = pack_object_header_info(data) total_rela_offset = None # set later, actual offset until data stream begins delta_info = None # OFFSET DELTA if type_id == OFS_DELTA: i = data_rela_offset c = ord(data[i]) i += 1 delta_offset = c & 0x7f while c & 0x80: c = ord(data[i]) i += 1 delta_offset += 1 delta_offset = (delta_offset << 7) + (c & 0x7f) # END character loop delta_info = delta_offset total_rela_offset = i # REF DELTA elif type_id == REF_DELTA: total_rela_offset = data_rela_offset+20 ref_sha = data[data_rela_offset:total_rela_offset] delta_info = ref_sha # BASE OBJECT else: # assume its a base object total_rela_offset = data_rela_offset # END handle type id abs_data_offset = offset + total_rela_offset if as_stream: stream = DecompressMemMapReader(buffer(data, total_rela_offset), False, uncomp_size) if delta_info is None: return abs_data_offset, OPackStream(offset, type_id, uncomp_size, stream) else: return abs_data_offset, ODeltaPackStream(offset, type_id, uncomp_size, delta_info, stream) else: if delta_info is None: return abs_data_offset, OPackInfo(offset, type_id, uncomp_size) else: return abs_data_offset, ODeltaPackInfo(offset, type_id, uncomp_size, delta_info) # END handle info # END handle stream #} END utilities class PackIndexFile(LazyMixin): """A pack index provides offsets into the corresponding pack, allowing to find locations for offsets faster.""" # Dont use slots as we dynamically bind functions for each version, need a dict for this # The slots you see here are just to keep track of our instance variables # __slots__ = ('_indexpath', '_fanout_table', '_data', '_version', # '_sha_list_offset', '_crc_list_offset', '_pack_offset', '_pack_64_offset') # used in v2 indices _sha_list_offset = 8 + 1024 def __init__(self, indexpath): super(PackIndexFile, self).__init__() self._indexpath = indexpath def _set_cache_(self, attr): if attr == "_packfile_checksum": self._packfile_checksum = self._data[-40:-20] elif attr == "_packfile_checksum": self._packfile_checksum = self._data[-20:] elif attr == "_data": # Note: We don't lock the file when reading as we cannot be sure # that we can actually write to the location - it could be a read-only # alternate for instance self._data = file_contents_ro_filepath(self._indexpath) else: # now its time to initialize everything - if we are here, someone wants # to access the fanout table or related properties # CHECK VERSION self._version = (self._data[:4] == '\377tOc' and 2) or 1 if self._version == 2: version_id = unpack_from(">L", self._data, 4)[0] assert version_id == self._version, "Unsupported index version: %i" % version_id # END assert version # SETUP FUNCTIONS # setup our functions according to the actual version for fname in ('entry', 'offset', 'sha', 'crc'): setattr(self, fname, getattr(self, "_%s_v%i" % (fname, self._version))) # END for each function to initialize # INITIALIZE DATA # byte offset is 8 if version is 2, 0 otherwise self._initialize() # END handle attributes #{ Access V1 def _entry_v1(self, i): """:return: tuple(offset, binsha, 0)""" return unpack_from(">L20s", self._data, 1024 + i*24) + (0, ) def _offset_v1(self, i): """see ``_offset_v2``""" return unpack_from(">L", self._data, 1024 + i*24)[0] def _sha_v1(self, i): """see ``_sha_v2``""" base = 1024 + (i*24)+4 return self._data[base:base+20] def _crc_v1(self, i): """unsupported""" return 0 #} END access V1 #{ Access V2 def _entry_v2(self, i): """:return: tuple(offset, binsha, crc)""" return (self._offset_v2(i), self._sha_v2(i), self._crc_v2(i)) def _offset_v2(self, i): """:return: 32 or 64 byte offset into pack files. 64 byte offsets will only be returned if the pack is larger than 4 GiB, or 2^32""" offset = unpack_from(">L", self._data, self._pack_offset + i * 4)[0] # if the high-bit is set, this indicates that we have to lookup the offset # in the 64 bit region of the file. The current offset ( lower 31 bits ) # are the index into it if offset & 0x80000000: offset = unpack_from(">Q", self._data, self._pack_64_offset + (offset & ~0x80000000) * 8)[0] # END handle 64 bit offset return offset def _sha_v2(self, i): """:return: sha at the given index of this file index instance""" base = self._sha_list_offset + i * 20 return self._data[base:base+20] def _crc_v2(self, i): """:return: 4 bytes crc for the object at index i""" return unpack_from(">L", self._data, self._crc_list_offset + i * 4)[0] #} END access V2 #{ Initialization def _initialize(self): """initialize base data""" self._fanout_table = self._read_fanout((self._version == 2) * 8) if self._version == 2: self._crc_list_offset = self._sha_list_offset + self.size() * 20 self._pack_offset = self._crc_list_offset + self.size() * 4 self._pack_64_offset = self._pack_offset + self.size() * 4 # END setup base def _read_fanout(self, byte_offset): """Generate a fanout table from our data""" d = self._data out = list() append = out.append for i in range(256): append(unpack_from('>L', d, byte_offset + i*4)[0]) # END for each entry return out #} END initialization #{ Properties def version(self): return self._version def size(self): """:return: amount of objects referred to by this index""" return self._fanout_table[255] def path(self): """:return: path to the packindexfile""" return self._indexpath def packfile_checksum(self): """:return: 20 byte sha representing the sha1 hash of the pack file""" return self._data[-40:-20] def indexfile_checksum(self): """:return: 20 byte sha representing the sha1 hash of this index file""" return self._data[-20:] def offsets(self): """:return: sequence of all offsets in the order in which they were written :note: return value can be random accessed, but may be immmutable""" if self._version == 2: # read stream to array, convert to tuple a = array.array('I') # 4 byte unsigned int, long are 8 byte on 64 bit it appears a.fromstring(buffer(self._data, self._pack_offset, self._pack_64_offset - self._pack_offset)) # networkbyteorder to something array likes more a.byteswap() return a else: return tuple(self.offset(index) for index in xrange(self.size())) # END handle version def sha_to_index(self, sha): """ :return: index usable with the ``offset`` or ``entry`` method, or None if the sha was not found in this pack index :param sha: 20 byte sha to lookup""" first_byte = ord(sha[0]) get_sha = self.sha lo = 0 # lower index, the left bound of the bisection if first_byte != 0: lo = self._fanout_table[first_byte-1] hi = self._fanout_table[first_byte] # the upper, right bound of the bisection # bisect until we have the sha while lo < hi: mid = (lo + hi) / 2 c = cmp(sha, get_sha(mid)) if c < 0: hi = mid elif not c: return mid else: lo = mid + 1 # END handle midpoint # END bisect return None def partial_sha_to_index(self, partial_bin_sha, canonical_length): """ :return: index as in `sha_to_index` or None if the sha was not found in this index file :param partial_bin_sha: an at least two bytes of a partial binary sha :param canonical_length: lenght of the original hexadecimal representation of the given partial binary sha :raise AmbiguousObjectName:""" if len(partial_bin_sha) < 2: raise ValueError("Require at least 2 bytes of partial sha") first_byte = ord(partial_bin_sha[0]) get_sha = self.sha lo = 0 # lower index, the left bound of the bisection if first_byte != 0: lo = self._fanout_table[first_byte-1] hi = self._fanout_table[first_byte] # the upper, right bound of the bisection # fill the partial to full 20 bytes filled_sha = partial_bin_sha + '\0'*(20 - len(partial_bin_sha)) # find lowest while lo < hi: mid = (lo + hi) / 2 c = cmp(filled_sha, get_sha(mid)) if c < 0: hi = mid elif not c: # perfect match lo = mid break else: lo = mid + 1 # END handle midpoint # END bisect if lo < self.size(): cur_sha = get_sha(lo) if is_equal_canonical_sha(canonical_length, partial_bin_sha, cur_sha): next_sha = None if lo+1 < self.size(): next_sha = get_sha(lo+1) if next_sha and next_sha == cur_sha: raise AmbiguousObjectName(partial_bin_sha) return lo # END if we have a match # END if we found something return None if 'PackIndexFile_sha_to_index' in globals(): # NOTE: Its just about 25% faster, the major bottleneck might be the attr # accesses def sha_to_index(self, sha): return PackIndexFile_sha_to_index(self, sha) # END redefine heavy-hitter with c version #} END properties class PackFile(LazyMixin): """A pack is a file written according to the Version 2 for git packs As we currently use memory maps, it could be assumed that the maximum size of packs therefor is 32 bit on 32 bit systems. On 64 bit systems, this should be fine though. :note: at some point, this might be implemented using streams as well, or streams are an alternate path in the case memory maps cannot be created for some reason - one clearly doesn't want to read 10GB at once in that case""" __slots__ = ('_packpath', '_data', '_size', '_version') # offset into our data at which the first object starts first_object_offset = 3*4 # header bytes footer_size = 20 # final sha def __init__(self, packpath): self._packpath = packpath def _set_cache_(self, attr): if attr == '_data': self._data = file_contents_ro_filepath(self._packpath) # read the header information type_id, self._version, self._size = unpack_from(">4sLL", self._data, 0) # TODO: figure out whether we should better keep the lock, or maybe # add a .keep file instead ? else: # must be '_size' or '_version' # read header info - we do that just with a file stream type_id, self._version, self._size = unpack(">4sLL", open(self._packpath).read(12)) # END handle header def _iter_objects(self, start_offset, as_stream=True): """Handle the actual iteration of objects within this pack""" data = self._data content_size = len(data) - self.footer_size cur_offset = start_offset or self.first_object_offset null = NullStream() while cur_offset < content_size: data_offset, ostream = pack_object_at(data, cur_offset, True) # scrub the stream to the end - this decompresses the object, but yields # the amount of compressed bytes we need to get to the next offset stream_copy(ostream.read, null.write, ostream.size, chunk_size) cur_offset += (data_offset - ostream.pack_offset) + ostream.stream.compressed_bytes_read() # if a stream is requested, reset it beforehand # Otherwise return the Stream object directly, its derived from the # info object if as_stream: ostream.stream.seek(0) yield ostream # END until we have read everything #{ Pack Information def size(self): """:return: The amount of objects stored in this pack""" return self._size def version(self): """:return: the version of this pack""" return self._version def data(self): """ :return: read-only data of this pack. It provides random access and usually is a memory map""" return self._data def checksum(self): """:return: 20 byte sha1 hash on all object sha's contained in this file""" return self._data[-20:] def path(self): """:return: path to the packfile""" return self._packpath #} END pack information #{ Pack Specific def collect_streams(self, offset): """ :return: list of pack streams which are required to build the object at the given offset. The first entry of the list is the object at offset, the last one is either a full object, or a REF_Delta stream. The latter type needs its reference object to be locked up in an ODB to form a valid delta chain. If the object at offset is no delta, the size of the list is 1. :param offset: specifies the first byte of the object within this pack""" out = list() while True: ostream = pack_object_at(self._data, offset, True)[1] out.append(ostream) if ostream.type_id == OFS_DELTA: offset = ostream.pack_offset - ostream.delta_info else: # the only thing we can lookup are OFFSET deltas. Everything # else is either an object, or a ref delta, in the latter # case someone else has to find it break # END handle type # END while chaining streams return out #} END pack specific #{ Read-Database like Interface def info(self, offset): """Retrieve information about the object at the given file-absolute offset :param offset: byte offset :return: OPackInfo instance, the actual type differs depending on the type_id attribute""" return pack_object_at(self._data, offset or self.first_object_offset, False)[1] def stream(self, offset): """Retrieve an object at the given file-relative offset as stream along with its information :param offset: byte offset :return: OPackStream instance, the actual type differs depending on the type_id attribute""" return pack_object_at(self._data, offset or self.first_object_offset, True)[1] def stream_iter(self, start_offset=0): """ :return: iterator yielding OPackStream compatible instances, allowing to access the data in the pack directly. :param start_offset: offset to the first object to iterate. If 0, iteration starts at the very first object in the pack. :note: Iterating a pack directly is costly as the datastream has to be decompressed to determine the bounds between the objects""" return self._iter_objects(start_offset, as_stream=True) #} END Read-Database like Interface class PackEntity(LazyMixin): """Combines the PackIndexFile and the PackFile into one, allowing the actual objects to be resolved and iterated""" __slots__ = ( '_index', # our index file '_pack', # our pack file '_offset_map' # on demand dict mapping one offset to the next consecutive one ) IndexFileCls = PackIndexFile PackFileCls = PackFile def __init__(self, pack_or_index_path): """Initialize ourselves with the path to the respective pack or index file""" basename, ext = os.path.splitext(pack_or_index_path) self._index = self.IndexFileCls("%s.idx" % basename) # PackIndexFile instance self._pack = self.PackFileCls("%s.pack" % basename) # corresponding PackFile instance def _set_cache_(self, attr): # currently this can only be _offset_map offsets_sorted = sorted(self._index.offsets()) last_offset = len(self._pack.data()) - self._pack.footer_size assert offsets_sorted, "Cannot handle empty indices" offset_map = None if len(offsets_sorted) == 1: offset_map = { offsets_sorted[0] : last_offset } else: iter_offsets = iter(offsets_sorted) iter_offsets_plus_one = iter(offsets_sorted) iter_offsets_plus_one.next() consecutive = izip(iter_offsets, iter_offsets_plus_one) offset_map = dict(consecutive) # the last offset is not yet set offset_map[offsets_sorted[-1]] = last_offset # END handle offset amount self._offset_map = offset_map def _sha_to_index(self, sha): """:return: index for the given sha, or raise""" index = self._index.sha_to_index(sha) if index is None: raise BadObject(sha) return index def _iter_objects(self, as_stream): """Iterate over all objects in our index and yield their OInfo or OStream instences""" indexfile = self._index _object = self._object for index in xrange(indexfile.size()): sha = indexfile.sha(index) yield _object(sha, as_stream, index) # END for each index def _object(self, sha, as_stream, index=-1): """:return: OInfo or OStream object providing information about the given sha :param index: if not -1, its assumed to be the sha's index in the IndexFile""" # its a little bit redundant here, but it needs to be efficient if index < 0: index = self._sha_to_index(sha) if sha is None: sha = self._index.sha(index) # END assure sha is present ( in output ) offset = self._index.offset(index) type_id, uncomp_size, data_rela_offset = pack_object_header_info(buffer(self._pack._data, offset)) if as_stream: if type_id not in delta_types: packstream = self._pack.stream(offset) return OStream(sha, packstream.type, packstream.size, packstream.stream) # END handle non-deltas # produce a delta stream containing all info # To prevent it from applying the deltas when querying the size, # we extract it from the delta stream ourselves streams = self.collect_streams_at_offset(offset) buf = streams[0].read(512) offset, src_size = msb_size(buf) offset, target_size = msb_size(buf, offset) streams[0].stream.seek(0) # assure it can be read by the delta reader dstream = DeltaApplyReader.new(streams) return OStream(sha, dstream.type, target_size, dstream) else: if type_id not in delta_types: return OInfo(sha, type_id_to_type_map[type_id], uncomp_size) # END handle non-deltas # deltas are a little tougher - unpack the first bytes to obtain # the actual target size, as opposed to the size of the delta data streams = self.collect_streams_at_offset(offset) buf = streams[0].read(512) offset, src_size = msb_size(buf) offset, target_size = msb_size(buf, offset) # collect the streams to obtain the actual object type if streams[-1].type_id in delta_types: raise BadObject(sha, "Could not resolve delta object") return OInfo(sha, streams[-1].type, target_size) # END handle stream #{ Read-Database like Interface def info(self, sha): """Retrieve information about the object identified by the given sha :param sha: 20 byte sha1 :raise BadObject: :return: OInfo instance, with 20 byte sha""" return self._object(sha, False) def stream(self, sha): """Retrieve an object stream along with its information as identified by the given sha :param sha: 20 byte sha1 :raise BadObject: :return: OStream instance, with 20 byte sha""" return self._object(sha, True) def info_at_index(self, index): """As ``info``, but uses a PackIndexFile compatible index to refer to the object""" return self._object(None, False, index) def stream_at_index(self, index): """As ``stream``, but uses a PackIndexFile compatible index to refer to the object""" return self._object(None, True, index) #} END Read-Database like Interface #{ Interface def pack(self): """:return: the underlying pack file instance""" return self._pack def index(self): """:return: the underlying pack index file instance""" return self._index def is_valid_stream(self, sha, use_crc=False): """ Verify that the stream at the given sha is valid. :param use_crc: if True, the index' crc for the sha is used to determine :param sha: 20 byte sha1 of the object whose stream to verify whether the compressed stream of the object is valid. If it is a delta, this only verifies that the delta's data is valid, not the data of the actual undeltified object, as it depends on more than just this stream. If False, the object will be decompressed and the sha generated. It must match the given sha :return: True if the stream is valid :raise UnsupportedOperation: If the index is version 1 only :raise BadObject: sha was not found""" if use_crc: if self._index.version() < 2: raise UnsupportedOperation("Version 1 indices do not contain crc's, verify by sha instead") # END handle index version index = self._sha_to_index(sha) offset = self._index.offset(index) next_offset = self._offset_map[offset] crc_value = self._index.crc(index) # create the current crc value, on the compressed object data # Read it in chunks, without copying the data crc_update = zlib.crc32 pack_data = self._pack.data() cur_pos = offset this_crc_value = 0 while cur_pos < next_offset: rbound = min(cur_pos + chunk_size, next_offset) size = rbound - cur_pos this_crc_value = crc_update(buffer(pack_data, cur_pos, size), this_crc_value) cur_pos += size # END window size loop # crc returns signed 32 bit numbers, the AND op forces it into unsigned # mode ... wow, sneaky, from dulwich. return (this_crc_value & 0xffffffff) == crc_value else: shawriter = Sha1Writer() stream = self._object(sha, as_stream=True) # write a loose object, which is the basis for the sha write_object(stream.type, stream.size, stream.read, shawriter.write) assert shawriter.sha(as_hex=False) == sha return shawriter.sha(as_hex=False) == sha # END handle crc/sha verification return True def info_iter(self): """ :return: Iterator over all objects in this pack. The iterator yields OInfo instances""" return self._iter_objects(as_stream=False) def stream_iter(self): """ :return: iterator over all objects in this pack. The iterator yields OStream instances""" return self._iter_objects(as_stream=True) def collect_streams_at_offset(self, offset): """ As the version in the PackFile, but can resolve REF deltas within this pack For more info, see ``collect_streams`` :param offset: offset into the pack file at which the object can be found""" streams = self._pack.collect_streams(offset) # try to resolve the last one if needed. It is assumed to be either # a REF delta, or a base object, as OFFSET deltas are resolved by the pack if streams[-1].type_id == REF_DELTA: stream = streams[-1] while stream.type_id in delta_types: if stream.type_id == REF_DELTA: sindex = self._index.sha_to_index(stream.delta_info) if sindex is None: break stream = self._pack.stream(self._index.offset(sindex)) streams.append(stream) else: # must be another OFS DELTA - this could happen if a REF # delta we resolve previously points to an OFS delta. Who # would do that ;) ? We can handle it though stream = self._pack.stream(stream.delta_info) streams.append(stream) # END handle ref delta # END resolve ref streams # END resolve streams return streams def collect_streams(self, sha): """ As ``PackFile.collect_streams``, but takes a sha instead of an offset. Additionally, ref_delta streams will be resolved within this pack. If this is not possible, the stream will be left alone, hence it is adivsed to check for unresolved ref-deltas and resolve them before attempting to construct a delta stream. :param sha: 20 byte sha1 specifying the object whose related streams you want to collect :return: list of streams, first being the actual object delta, the last being a possibly unresolved base object. :raise BadObject:""" return self.collect_streams_at_offset(self._index.offset(self._sha_to_index(sha))) #} END interface