'\" te
.\" Copyright (c) 2000, Sun Microsystems, Inc. All Rights Reserved.
.\" Copyright 1989 AT&T
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
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.TH MSGB 9S "Apr 11, 1991"
.SH NAME
msgb, mblk \- STREAMS message block structure
.SH SYNOPSIS
.LP
.nf
#include <sys/stream.h>
.fi

.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 1 (DDI/DKI)
.SH DESCRIPTION
.sp
.LP
A STREAMS message is made up of one or more message blocks, referenced by a
pointer to a \fBmsgb\fR structure. The \fBb_next\fR and  \fBb_prev\fR pointers
are used to link messages together on a \fBQUEUE\fR. The  \fBb_cont\fR pointer
links message blocks together when a message consists of more than one block.
.sp
.LP
Each  \fBmsgb\fR structure also includes a pointer to a  \fBdatab\fR(9S)
structure, the data block (which contains pointers to the actual data of the
message), and the type of the message.
.SH STRUCTURE MEMBERS
.sp
.in +2
.nf
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  */
.fi
.in -2

.sp
.LP
Valid flags are as follows:
.sp
.ne 2
.na
\fB\fBMSGMARK\fR \fR
.ad
.RS 13n
Last byte of message is marked.
.RE

.sp
.ne 2
.na
\fB\fBMSGDELIM\fR \fR
.ad
.RS 13n
Message is delimited.
.RE

.sp
.LP
The \fBmsgb\fR structure is defined as type \fBmblk_t\fR.
.SH SEE ALSO
.sp
.LP
.BR datab (9S)
.sp
.LP
\fIWriting Device Drivers\fR
.sp
.LP
\fISTREAMS Programming Guide\fR