886                              const char fourcc[4], int chunk_num) {  in GetChunk()  argument
893     if (count == chunk_num) break;  in GetChunk()
898 static int SetChunk(const char fourcc[4], int chunk_num,  in SetChunk()  argument
903   if (dmux == NULL || fourcc == NULL || chunk_num < 0) return 0;  in SetChunk()
906   if (chunk_num == 0) chunk_num = count;  in SetChunk()
908   if (chunk_num <= count) {  in SetChunk()
910     const Chunk* const chunk = GetChunk(dmux, fourcc, chunk_num);  in SetChunk()
914     iter->chunk_num   = chunk_num;  in SetChunk()
921                       const char fourcc[4], int chunk_num,  in WebPDemuxGetChunk()  argument
927   return SetChunk(fourcc, chunk_num, iter);  in WebPDemuxGetChunk()
934     return SetChunk(fourcc, iter->chunk_num + 1, iter);  in WebPDemuxNextChunk()
940   if (iter != NULL && iter->chunk_num > 1) {  in WebPDemuxPrevChunk()
943     return SetChunk(fourcc, iter->chunk_num - 1, iter);  in WebPDemuxPrevChunk()