flushq.9

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.so lis.macros
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.\"
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.TH FLUSHQ 9 "2004/01/12 23:33:00" "LiS-2_16_18-8" "Linux STREAMS DDI/DKI"
.SH NAME
.B flushq
\- flushes messages from a \fISTREAMS\fR message queue
.SH SYNOPSIS
.PP
.B #include <sys/stream.h>
.HP 8
.BI "flushq(queue_t *" q ", int " flag );
.SH DESCRIPTION
.PP
.BR flushq ()
is used to flush messages from a
.IR STREAMS (4)
message queue.  It is typically
called in a
.B M_FLUSH
handling routine to flush the requested messages from a queue.
.PP
The arguments to
.B flushq
are interpreted as follows:
.TP 8
.I q
The queue to flush.
.TP 8
.I flag
How to flush the queue.
.I flag
can be one of the following:
.RS
.TP 12
.B FLUSHDATA
Flush only data messages; do not flush the control messages from the queue.
.TP 12
.B FLUSHALL
Flush all the messages from queue: both data messages and control messages.
.RE
.SH EXAMPLES
.PP
.BR flushq ()
is normally used within the
.B M_FLUSH
handling procedures for a
.IR STREAMS (4)
module or driver as follows:
.sp
.in +4
.nf
\fC\s-2\
int x_w_flush(queue_t *q, mblk_t *mp)
{
    if (*mp->b_rptr & FLUSHW) {
        if (*mp->b_rptr & FLUSHBAND)
            flushband(WR(q), mp->b_rptr[1], FLUSHALL);
        else
            flushq(WR(q), FLUSHALL);
        if (q->q_next) {
            putnext(q, mp);
            return (0);
        }
        *mp->b_rptr &= ~FLUSHW;
    }
    if (*mp->b_rptr & FLUSHR) {
        if (*mp->b_rptr & FLUSHBAND)
            flushband(RD(q), mp->b_rptr[1], FLUSHALL);
        else
            flushq(RD(q), FLUSHALL);
        if (!q->q_next) {
            qreply(q, mp);
            return (0);
        }
        *mp->b_rptr &= ~FLUSHR;
    }
    freemsg(mp);
    return (0);
}
int x_r_flush(queue_t *q, mblk_t *mp)
{
    if (*mp->b_rptr & FLUSHR) {
        if (*mp->b_rptr & FLUSHBAND)
            flushband(RD(q), mp->b_rptr[1], FLUSHALL);
        else
            flushq(RD(q), FLUSHALL);
        if (q->q_next) {
            putnext(q, mp);
            return (0);
        }
        *mp->b_rptr &= ~FLUSHR;
    }
    if (*mp->b_rptr & FLUSHW) {
        if (*mp->b_rptr & FLUSHBAND)
            flushband(WR(q), mp->b_rptr[1], FLUSHALL);
        else
            flushq(WR(q), FLUSHALL);
        if (!q->q_next) {
            qreply(q, mp);
            return (0);
        }
        *mp->b_rptr &= ~FLUSHW;
    }
    freemsg(mp);
    return (0);
}
\s+2\fR
.fi
.PP
In addition,
.BR flushq ()
is often used when closing or
.BR I_UNLINK ing
a stream as follows:
.sp
.in +4
.nf
\fC\s-2\
void x_free_priv(queue_t *q)
{
    priv_t *p = (priv_t *) q->q_ptr;
    flushq(RD(q), FLUSHALL);
    flushq(WR(q), FLUSHALL);
    /* free some more stuff */
    free(p);
    RD(q)->q_ptr = WR(q)->q_ptr = NULL;
    return;
}
\s+2\fR
.fi
.SH "RETURN VALUES"
.PP
.BR flushq ()
returns
.BR void .
.SH ERRORS
.PP
If the
.I q
passed to
.BR flushq ()
is
.BR NULL ,
or the
.I q
does not point to a valid queue structure, then
.BR flushq ()
will silently fail.
.SH CAVEATS
.PP
.B LiS
.[
LiS
.]
implements the call to
.BR flushq (9)
.BI flushq( q ", " band )
as a call to
.BI flushband( q ", " 0 ", " flag ).
.SH "SEE ALSO"
.PP
.BR flushband (9).
.SH VERSIONS
.PP
This manpage was written for
.B LiS\c
.
.[
LiS
.]
.PP
.BR flushq ()
first appeared in SVR 3.
.[
svr3
.]
.\"
.\"
.XX
.[
magic
.]
.[
svr42
.]
.[
svr4
.]
.\"
.\"
.[
$LIST$
.]
.TA