solaris Man Page: putctl(9f)

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putctl(9F) manual page Table of Contents

Name

putctl - send a control message to a queue

Synopsis

#include <sys/stream.h>

int putctl(queue_t *q, int type);

Interface Level

Architecture independent level 1 (DDI/DKI).

Arguments

q: Queue to which the message is to be sent.
type: Message type (must be control, not data type).

putctl() tests the type argument to make sure a data type has not been specified, and then attempts to allocate a message block. putctl fails if type is M_DATA , M_PROTO , or M_PCPROTO , or if a message block cannot be allocated. If successful, putctl() calls the put(9E) routine of the queue pointed to by q with the newly allocated and initialized messages.

Return Values

On success, 1 is returned. If type is a data type, or if a message block cannot be allocated, 0 is returned.

Context

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

Example

The send_ctl routine is used to pass control messages downstream. M_BREAK messages are handled with putctl() (line 11). putctl1(9F) (line 16) is used for M_DELAY messages, so that parm can be used to specify the length of the delay. In either case, if a message block cannot be allocated a variable recording the number of allocation failures is incremented (lines 12, 17). If an invalid message type is detected, cmn_err(9F) panics the system (line 21).

 1  void
 2  send_ctl(wrq, type, parm)
 3      queue_t *wrq;
 4      unchar type;
 5      unchar parm;
 6  {
 7    extern int num_alloc_fail;
 8
 9    switch (type) {
10    case M_BREAK:
11        if (!putctl(wrq->q_next, M_BREAK))
12            num_alloc_fail++;
13        break;
14
15    case M_DELAY:
16        if (!putctl1(wrq->q_next, M_DELAY, parm))
17            num_alloc_fail++;
18        break;
19
20    default:
21        cmn_err(CE_PANIC, "send_ctl: bad message type passed");
22        break;
23    }
24  }