'Initialize a SwiftPackReader
:param scon: a `SwiftConnector` instance
:param filename: the pack filename
:param pack_length: The size of the pack object'

def __init__(self, scon, filename, pack_length):

    self.scon = scon
    self.filename = filename
    self.pack_length = pack_length
    self.offset = 0
    self.base_offset = 0
    self.buff = ''
    self.buff_length = self.scon.chunk_length
