If the chunk was descended into using mmioDescend, then mmioAscend seeks to the location following the end of the chunk (past the extra pad byte, if any). If the chunk was created and descended into using mmioCreateChunk or if the MMIO_DIRTY flag in the ulFlags field (of the MMCKINFO structure passed in the pckinfo parameter) is set, then the current file position is assumed to mark the end of the data portion of the chunk. If the chunk size is not the same as the value that was stored in the ckSize field of MMCKINFO before mmioCreateChunk or mmioDescend was called, then mmioAscend seeks back and corrects the chunk size in the chunk header before ascending from the chunk. Also, if the chunk size is odd, then mmioAscend writes a NULL pad byte at the end of the chunk.