msgb(9S)

NAME

     msgb, mblk - STREAMS message block structure

SYNOPSIS

     #include <sys/stream.h>

INTERFACE LEVEL

     Architecture independent level 1 (DDI/DKI)

DESCRIPTION

     A STREAMS message is made up of one or more message  blocks,
     referenced  by a pointer to a msgb structure. The b_next and
     b_prev pointers are used to  link  messages  together  on  a
     QUEUE.  The   b_cont  pointer  links message blocks together
     when a message consists of more than one block.

     Each  msgb structure also includes a pointer to a  datab(9S)
     structure,  the  data  block (which contains pointers to the
     actual data of the message), and the type of the message.

STRUCTURE MEMBERS

     struct msgb     *b_next;           /* next message on queue */
     struct msgb     *b_prev;           /* previous message on queue */
     struct msgb     *b_cont;           /* next message block */
     unsigned char   *b_rptr;           /* 1st unread data byte of buffer */
     unsigned char   *b_wptr;           /* 1st unwritten data byte of buffer */
     struct datab    *b_datap;          /* pointer to data block */
     unsigned char   b_band;            /* message priority  */
     unsigned short  b_flag;            /* used by stream head  */

     Valid flags are as follows:

          MSGMARK
                Last byte of message is marked.

          MSGDELIM
                Message is delimited.

     The msgb structure is defined as type mblk_t.

SEE ALSO

     datab(9S)

     Writing Device Drivers

     STREAMS Programming Guide