This data structure contains fields for the DDCMD_READ and DDCMD_WRITE messages.
typedef struct _ddcmd_readwrite_parm { ULONG ulFunction; /* Function requested by stream handler. */ HSTREAM hStream; /* Stream handle. */ PVOID pBuffer; /* Buffer pointer. */ ULONG ulBufferSize; /* Buffer size. */ PVOID pProcessLin; /* Process linear record pointer. */ BOOL fEOS; /* Whether or not this is the EOS buffer. */ ULONG ulParm1; /* Reserved for future use. */ ULONG ulParm2; /* Reserved for future use. */ ULONG ulLength; /* Length of the structure. */ } DDCMDREADWRITE;