.IX \f4pcmsg\fP(D3DK)
.IX STREAMS messages

NAME

pcmsg − test whether a message is a priority control message

SYNOPSIS

#include <sys/types.h>
#include <sys/stream.h>
#include <sys/ddi.h>
int pcmsg(uchar_t type);

ARGUMENTS

typeThe type of message to be tested. 

DESCRIPTION

The pcmsg function tests the type of message to determine if it is a priority control message (also known as a high priority message.)  The db_type field of the datab(D4DK) structure contains the message type.  This field may be accessed through the message block using mp->b_datap->db_type.  .IX STREAMS messages

RETURN VALUE

pcmsg returns 1 if the message is a priority control message and 0 if the message is any other type. 

LEVEL

Base or Interrupt. 

NOTES

Does not sleep.  Driver defined basic locks, read/write locks, and sleep locks may be held across calls to this function.

SEE ALSO

allocb(D3DK), datab(D4DK), msgb(D4DK), messages(D5DK)

EXAMPLE

.IX \f4canputnext\fP(D3DK), example
.IX \f4pcmsg\fP(D3DK), example
.IX \f4putbq\fP(D3DK), example
.IX \f4putnext\fP(D3DK), example

The service routine processes messages on the queue.  If the message is a high priority message, or if it is a normal message and the stream is not flow-controlled, the message is processed and passed along in the stream.  Otherwise, the message is placed back on the head of the queue and the service routine returns. 

 1xxxsrv(q)
 2queue_t ∗q;
 3{
 4mblk_t ∗mp;
  5while ((mp = getq(q)) != NULL) {
 6if (pcmsg(mp->b_datap->db_type) || canputnext(q)) {
 7/∗ process message ∗/
 8putnext(q, mp);
 9} else {
10putbq(q, mp);
11return;
12}
13}
14}

DDI/DKI  —  STREAMS