static int get_packetheader(NUTContext *nut, ByteIOContext *bc, int calculate_checksum) { int64_t start, size; start= url_ftell(bc) - 8; init_checksum(bc, calculate_checksum ? update_adler32 : NULL, 0); size= get_v(bc); nut->packet_start[2] = start; nut->written_packet_size= size; return size; }