doc/examples: add cds_wfcq_dequeue

[urcu.git] / doc / examples / wfcqueue / cds_wfcq_dequeue.c

diff --git a/doc/examples/wfcqueue/cds_wfcq_dequeue.c b/doc/examples/wfcqueue/cds_wfcq_dequeue.c
new file mode 100644 (file)
index 0000000..6488d53
--- /dev/null
+++ b/doc/examples/wfcqueue/cds_wfcq_dequeue.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2013  Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+ * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+ *
+ * Permission is hereby granted to use or copy this program for any
+ * purpose,  provided the above notices are retained on all copies.
+ * Permission to modify the code and to distribute modified code is
+ * granted, provided the above notices are retained, and a notice that
+ * the code was modified is included with the above copyright notice.
+ *
+ * This example shows how to dequeue nodes from a wfcqueue.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <urcu/wfcqueue.h>     /* Wait-free concurrent queue */
+#include <urcu/compiler.h>     /* For CAA_ARRAY_SIZE */
+
+/*
+ * Nodes populated into the queue.
+ */
+struct mynode {
+       int value;                      /* Node content */
+       struct cds_wfcq_node node;      /* Chaining in queue */
+};
+
+int main(int argc, char **argv)
+{
+       int values[] = { -5, 42, 36, 24, };
+       struct cds_wfcq_head myqueue_head;      /* Queue head */
+       struct cds_wfcq_tail myqueue_tail;      /* Queue tail */
+       unsigned int i;
+       int ret = 0;
+
+       cds_wfcq_init(&myqueue_head, &myqueue_tail);
+
+       /*
+        * Adding nodes to the linked-list. Safe against concurrent
+        * RCU traversals, require mutual exclusion with list updates.
+        */
+       for (i = 0; i < CAA_ARRAY_SIZE(values); i++) {
+               struct mynode *node;
+
+               node = malloc(sizeof(*node));
+               if (!node) {
+                       ret = -1;
+                       goto end;
+               }
+
+               cds_wfcq_node_init(&node->node);
+               node->value = values[i];
+               cds_wfcq_enqueue(&myqueue_head, &myqueue_tail,
+                               &node->node);
+       }
+
+       /*
+        * Dequeue each node from the queue. Those will be dequeued from
+        * the oldest (first enqueued) to the newest (last enqueued).
+        */
+       printf("dequeued content:");
+       for (;;) {
+               struct cds_wfcq_node *qnode;
+               struct mynode *node;
+
+               qnode = cds_wfcq_dequeue_blocking(&myqueue_head, &myqueue_tail);
+               if (!qnode) {
+                       break;  /* Queue is empty. */
+               }
+               /* Getting the container structure from the node */
+               node = caa_container_of(qnode, struct mynode, node);
+               printf(" %d", node->value);
+               free(node);
+       }
+       printf("\n");
+end:
+       return ret;
+}