Four-byte buffer in which the system returns the number of bytes that were available in the named pipe.
typedef struct _AVAILDATA {
USHORT cbpipe; /* The number of bytes that were buffered in the pipe, including the message-header bytes and bytes that have been exa
mined. */
USHORT cbmessage; /* Number of bytes in the current message. */
} AVAILDATA;
typedef AVAILDATA * PAVAILDATA ;