To read a fragmented cluster, the client must know how many sectors, including the fragment header, that the cluster consumes. Because the MDFAT entry gives only the size of the first fragment, the client must either read the fragment header and compute the total sector count, or issue a raw read IOCTL in which the rci_data field of the RawClusterInfo structure is NULL. Raw reads where the rci_pdata field is NULL return no raw data, but they do fill in the other fields in the RawClusterInfo structure. When a fragmented cluster is actually read, the fragmented header is stripped from the data that is returned; that is, the first byte in the data buffer contains the first byte of the cluster's raw data.
RawClusterInfo