chunk.py 文件源码

def download(self, sm, target_file, overwrite = False):
        remote_chunk = "chunks/%s" % self.get_filename()
        tmp_file = target_file + ".download"

        # if file exists, try
        if os.path.exists(target_file):
            # overwrite check
            if not overwrite:
                raise ChirriException("Chunk file '%s' already exists." % target_file)

            # yep! chunk is already on disk.. decide what to do...
            eh = chirribackup.crypto.hash_file(target_file)
            if eh.hash != h:
                # hashes doesn't match... it is surely an old partial chunk of
                # a previous restore operation (cancelled), delete it from disk
                logger.warning("Old tmp download '%s' found but corrupt. Reloading again.")
                os.unlink(target_file)
            else:
                # hashes match, so it is the file that we need -- continue as
                # usual without downloading anything
                logger.info("Found previous temp download '%s' with matching hash. Recycling it.")
                return

        # ok... download raw chunk
        sm.download_file(remote_chunk, tmp_file)

        # decompress it
        if self.compression is None:
            os.rename(tmp_file, target_file)
        else:
            try:
                decompressor = chirribackup.compression.Decompressor(self.compression, target_file)
                sh = chirribackup.crypto.ChirriHasher()
                with open(tmp_file, 'rb') as ifile:
                    buf = ifile.read(READ_BLOCKSIZE)
                    while len(buf) > 0:
                        sh.update(decompressor.decompress(buf))
                        buf = ifile.read(READ_BLOCKSIZE)
                    sh.update(decompressor.close())

                if sh.hash != self.hash:
                    raise ChirriException("Bad data recovered (%s, %s)" \
                                            % (target_file, self.first_seen_as))

            except exceptions.IOError, ex:
                os.unlink(target_file)
                raise ChirriException("Cannot hash & copy file '%s': %s" % (source_file, ex))
            finally:
                os.unlink(tmp_file)