def align_after(self, offset):
        """
        Search for a sync point after offset and align just after that.
        """
        f = self.reader
        if offset <= 0:  # FIXME what is a negative offset??
            f.seek(0)
            self._block_count = 0
            self._read_header()  # FIXME we can't extimate how big it is...
            return
        sm = self.sync_marker
        sml = len(sm)
        pos = offset
        while pos < self.file_length - sml:
            f.seek(pos)
            data = f.read(self.FORWARD_WINDOW_SIZE)
            sync_offset = data.find(sm)
            if sync_offset > -1:
                f.seek(pos + sync_offset)
                self._block_count = 0
                return
            pos += len(data)
Search for a sync point after offset and align just after that.