freebsd man page for msgb

msgb(9S)						    Data Structures for Drivers 						  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

SunOS 5.10							    11 Apr 1991 							  msgb(9S)