insq(9F)

NAME | SYNOPSIS | PARAMETERS | INTERFACE LEVEL | DESCRIPTION | RETURN VALUES | CONTEXT | EXAMPLES | SUMMARY OF TRUSTED SOLARIS CHANGES | SEE ALSO | WARNINGS | NOTES

NAME

insq– Insert a message into a queue

SYNOPSIS

#include <sys/stream.h>

int insq(queue_t *q, mblk_t *emp, mblk_t *nmp);

PARAMETERS

q

Pointer to the queue containing message emp.

emp

Enqueued message before which the new message is to be inserted. mblk_t is an instance of the msgb(9S) structure.

nmp

Message to be inserted.

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

DESCRIPTION

insq() inserts a message into a queue. The message to be inserted, nmp, is placed in q immediately before the message emp. If emp is NULL, the new message is placed at the end of the queue. The queue class of the new message is ignored. All flow control parameters are updated. The service procedure is enabled unless QNOENB is set.

RETURN VALUES

insq() returns:

1

On success.

0

On failure.

CONTEXT

insq() can be called from user or interrupt context.

EXAMPLES

This routine illustrates the steps a transport provider may take to place expedited data ahead of normal data on a queue (assume all M_DATA messages are converted into M_PROTO T_DATA_REQ messages). Normal T_DATA_REQ messages are just placed on the end of the queue (line 16). However, expedited T_EXDATA_REQ messages are inserted before any normal messages already on the queue (line 25). If there are no normal messages on the queue, bp will be NULL and we fall out of the for loop (line 21). insq() acts like putq(9F) in this case.

      1  #include <sys/tihdr.h>
      2  #include <sys/stream.h>
      3
      4  static int
      5  xxxwput(queue_t *q, mblk_t *mp)
      6  {
      7   union T_primitives *tp;
      8   mblk_t *bp;
      9   union T_primitives *ntp;
     10
     11   switch (mp->b_datap->db_type) {
     12   case M_PROTO:
     13        tp = (union T_primitives *)mp->b_rptr;
     14        switch (tp->type) {
     15        case T_DATA_REQ:
     16                putq(q, mp);
     17                break;
     18
     19        case T_EXDATA_REQ:
     20                freezestr(q);
     21                for (bp = q->q_first; bp; bp = bp->b_next) {
     22                   if (bp->b_datap->db_type == M_PROTO) {
     23                     ntp = (union T_primitives *)bp->b_rptr;
     24                     if (ntp->type != T_EXDATA_REQ)
     25                         break;
     26                  }
     27                }
     28                (void)insq(q, bp, mp);
     29                unfreezestr(q);
     30                break;
               . . .
     31              }
     32   }
     33  }

SUMMARY OF TRUSTED SOLARIS CHANGES

This routine will try to assign attribute structures to the mblks of a message that does not have one. The first attribute stucture found will be used. If a stream module illegally combined messages, mblks can have different attribute structures; in that case, the message will be dropped by this routine unless overridden by the TSOL_STR_LINKB flag.

SEE ALSO

Trusted Solaris 8 HW 12/02 Reference Manual

Intro(9F), putq(9F)

SunOS 5.8 Reference Manual

freezestr(9F), rmvq(9F), unfreezestr(9F), msgb(9S)

Writing Device Drivers

STREAMS Programming Guide

WARNINGS

If emp is non-NULL, it must point to a message on q or a system panic could result.

NOTES

The stream must be frozen using freezestr(9F) before calling insq().

These interfaces are uncommitted. Although not expected to do so, they may change between minor Trusted Solaris releases.

SunOS 5.8  Last Revised 22 Oct 1996

NAME | SYNOPSIS | PARAMETERS | INTERFACE LEVEL | DESCRIPTION | RETURN VALUES | CONTEXT | EXAMPLES | SUMMARY OF TRUSTED SOLARIS CHANGES | SEE ALSO | WARNINGS | NOTES