def _seek_writable_pos(self, map_handle):
        pos = 0
        while True:
            if pos + 4 <= self.store_file_size:
                size, = struct.unpack('I', map_handle[pos:pos+4])
                if size == 0:
                    return pos
                pos += (4 + size)
            else:
                return -1
        
        return -1
dataset/ETHPy150Open chineking/cola/cola/core/mq/store.py/Store._seek_writable_pos/original