doc/examples/wfcqueue/cds_wfcq_dequeue.c

   1 /*
   2  * Copyright (C) 2013  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   3  *
   4  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   5  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   6  *
   7  * Permission is hereby granted to use or copy this program for any
   8  * purpose,  provided the above notices are retained on all copies.
   9  * Permission to modify the code and to distribute modified code is
  10  * granted, provided the above notices are retained, and a notice that
  11  * the code was modified is included with the above copyright notice.
  12  *
  13  * This example shows how to dequeue nodes from a wfcqueue.
  14  */
  15
  16 #include <stdio.h>
  17 #include <stdlib.h>
  18
  19 #include <urcu/wfcqueue.h>      /* Wait-free concurrent queue */
  20 #include <urcu/compiler.h>      /* For CAA_ARRAY_SIZE */
  21
  22 /*
  23  * Nodes populated into the queue.
  24  */
  25 struct mynode {
  26         int value;                      /* Node content */
  27         struct cds_wfcq_node node;      /* Chaining in queue */
  28 };
  29
  30 int main(int argc, char **argv)
  31 {
  32         int values[] = { -5, 42, 36, 24, };
  33         struct cds_wfcq_head myqueue_head;      /* Queue head */
  34         struct cds_wfcq_tail myqueue_tail;      /* Queue tail */
  35         unsigned int i;
  36         int ret = 0;
  37
  38         cds_wfcq_init(&myqueue_head, &myqueue_tail);
  39
  40         /*
  41          * Enqueue nodes.
  42          */
  43         for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
  44                 struct mynode *node;
  45
  46                 node = malloc(sizeof(*node));
  47                 if (!node) {
  48                         ret = -1;
  49                         goto end;
  50                 }
  51
  52                 cds_wfcq_node_init(&node->node);
  53                 node->value = values[i];
  54                 cds_wfcq_enqueue(&myqueue_head, &myqueue_tail,
  55                                 &node->node);
  56         }
  57
  58         /*
  59          * Dequeue each node from the queue. Those will be dequeued from
  60          * the oldest (first enqueued) to the newest (last enqueued).
  61          */
  62         printf("dequeued content:");
  63         for (;;) {
  64                 struct cds_wfcq_node *qnode;
  65                 struct mynode *node;
  66
  67                 qnode = cds_wfcq_dequeue_blocking(&myqueue_head, &myqueue_tail);
  68                 if (!qnode) {
  69                         break;  /* Queue is empty. */
  70                 }
  71                 /* Getting the container structure from the node */
  72                 node = caa_container_of(qnode, struct mynode, node);
  73                 printf(" %d", node->value);
  74                 free(node);
  75         }
  76         printf("\n");
  77 end:
  78         cds_wfcq_destroy(&myqueue_head, &myqueue_tail);
  79         return ret;
  80 }