def __init__(self, scon, filename):
""" Initialize a SwiftPackReader
:param scon: a `SwiftConnector` instance
:param filename: the pack filename
"""
self.scon = scon
self._filename = filename
self._header_size = 12
headers = self.scon.get_object_stat(self._filename)
self.pack_length = int(headers['content-length'])
pack_reader = SwiftPackReader(self.scon, self._filename,
self.pack_length)
(version, self._num_objects) = read_pack_header(pack_reader.read)
self._offset_cache = LRUSizeCache(1024*1024*self.scon.cache_length,
compute_size=_compute_object_size)
self.pack = None
