zlib_adler32
strm->adler = zlib_adler32(strm->adler, strm->next_in, len);
#define UPDATE(check, buf, len) zlib_adler32(check, buf, len)
strm->adler = state->check = zlib_adler32(0L, NULL, 0);
strm->adler = state->check = zlib_adler32(0L, NULL, 0);