NAME

msgb - 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 is composed 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