Kernel Functions for Drivers                             insq(9F)



NAME
     insq - insert a message into a queue

SYNOPSIS
     #include 



     int insq(queuet *q, mblkt *emp, mblkt *nmp);


INTERFACE LEVEL
     Architecture independent level 1 (DI/DKI).

PARAMETERS
     q      Pointer to the queue containing message emp.


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


     nmp    Message to be inserted.


DESCRIPTION
     The insq() function inserts a message into a queue. The mes-
     sage  to be inserted, nmp, is placed in q immediately before
     the message emp. If emp is NUL, 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
     The insq() function returns 1 on success, and 0 on failure.

CONTEXT
     The insq() function can be called from user,  interrupt,  or
     kernel 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  MDATA  messages  are  converted  into  MPROTO
     TDATAREQ  messages).  Normal  TDATAREQ messages are just
     placed on the end of the queue (line 16). However, expedited
     TEXDATAREQ  messages  are  inserted before any normal mes-
     sages already on the queue (line 25). If there are no normal
     messages  on  the  queue, bp will be NUL and we fall out of
     the for loop (line 21). insq  acts  like  putq(9F)  in  this
     case.



SunOS 5.11          Last change: 16 Jan 2006                    1






Kernel Functions for Drivers                             insq(9F)



       1  #include
        2  #include
        3
        4  static int
        5  xxxwput(queuet *q, mblkt *mp)
        6  {
        7   union Tprimitives *tp;
        8   mblkt *bp;
        9   union Tprimitives *ntp;
       10
       11   switch (mp->bdatap->dbtype) {
       12   case MPROTO:
       13        tp = (union Tprimitives *)mp->brptr;
       14        switch (tp->type) {
       15        case TDATAREQ:
       16                putq(q, mp);
       17                break;
       18
       19        case TEXDATAREQ:
       20              /* Insert code here to protect queue and message block */
       21               for (bp = q->qfirst; bp; bp = bp->bnext) {
       22                  if (bp->bdatap->dbtype == MPROTO) {
       23                    ntp = (union Tprimitives *)bp->brptr;
       24                    if (ntp->type != TEXDATAREQ)
       25                        break;
       26                 }
       27               }
       28               (void)insq(q, bp, mp);
       29               /* End of region that must be protected */
       30               break;
                 . . .
       31              }
       32    }
       33   }



     When using insq(), you must ensure that the  queue  and  the
     message  block is not modified by another thread at the same
     time. You can achieve this either by using STREAMS functions
     or by implementing your own locking.

SEE ALSO
     putq(9F), rmvq(9F), msgb(9S)


     Writing Device Drivers


     STREAMS Programming Guide





SunOS 5.11          Last change: 16 Jan 2006                    2






Kernel Functions for Drivers                             insq(9F)



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




















































SunOS 5.11          Last change: 16 Jan 2006                    3