bf_write(is->bf, first_block, first_offset, sizeof(int)-gap,
&count);
memcpy (is->merge_buf, ((char*)&count)+(sizeof(int)-gap), gap);
bf_write(is->bf, first_block, first_offset, sizeof(int)-gap,
&count);
memcpy (is->merge_buf, ((char*)&count)+(sizeof(int)-gap), gap);