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This example depicts the canonical flushing code for STREAMS modules. The module has a write service procedure and potentially has messages on the queue. If it receives an M_FLUSH message, and if the FLUSHR bit is on in the first byte of the message (line 10), then the read queue is flushed (line 11). If the FLUSHW bit is on (line 12), then the write queue is flushed (line 13). Then the message is passed along to the next entity in the stream (line 14). See the example for qreply(9F) for the canonical flushing code for drivers.
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1 /*
2 * Module write-side put procedure.
3 */
4 xxxwput(q, mp)
5 queue_t *q;
6 mblk_t *mp;
7 {
8 switch(mp->b_datap->db_type) {
9 case M_FLUSH:
10 if (*mp->b_rptr & FLUSHR)
11 flushq(RD(q), FLUSHALL);
12 if (*mp->b_rptr & FLUSHW)
13 flushq(q, FLUSHALL);
14 putnext(q, mp);
15 break;
. . .
16 }
17 }
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