Buffer Header Format

This topic lists the common fields that always occur at the start of a buffer header. These are followed by further fields specific to the particular message; see FMI Message Formats for details of individual message formats.

PTRBFHDR  nxtqptr;
PTRBFELT  hdreptr;
CHAR      numelts;
CHAR      msgtype;
CHAR      srcl;
CHAR      srcp;
INTEGER   srci;
CHAR      destl;
CHAR      destp;
INTEGER   desti;
};

Members

nxtqptr
When the buffer is in a queue, this field points to the header of the next buffer in the queue (NULL if it is the last buffer in the queue). When the buffer is not in a queue, this field points to itself; the SNA Server buffer management routines use this to check for buffer corruption.
hdreptr
Pointer to the first buffer element in the associated chain of buffer elements; NULL if the message consists only of a buffer header.
numelts
Number of buffer elements chained from the header; zero if the message consists only of a buffer header.
msgtype
Message type. See individual message descriptions in FMI Message Formats.
srcl
Source locality. See LPI Addresses.
srcp
Source partner. See LPI Addresses.
srci
Source index. See LPI Addresses.
destl
Destination locality. See LPI Addresses.
destp
Destination partner. See LPI Addresses.
desti
Destination index. See LPI Addresses.

Note Fields that occupy two bytes, such as opresid in Open(PLU) Request, are normally represented with the arithmetically most significant byte in the lowest byte address, irrespective of the normal orientation used by the processor on which the software executes. That is, the 2-byte value 0x1234 has the byte 0x12 in the lowest byte address. However, the following fields are exceptions: