Hi,
As we see, DPDK ring has mainly the enqueue/dequeue APIs for SINGLE/MULTI
producer/consumer. I have a requirement in work to take a peek on the top
object in the ring. I don't want to consume it, just check the reference of the
object. How could this be supported? Or any alternative solution for my
requirement? Thanks.
I wrote my own simple peek interface but it's not MC-safe. I think it's
better if DPDK can support it officially.
/**
+ * Just take a peek on the top object from a ring but not consume it.
+ * Note: This interface is MC and multi-thread not safe.
+ * It can only be used for ring with RING_F_SC_DEQ attribute.
+ *
+ * @param r
+ * A pointer to the ring structure.
+ * @param obj_p
+ * A pointer to a void * pointer (object) that will be filled.
+ * @return
+ * - 0: Success, object is peeked.
+ * - -ENOENT: Not entries in the ring.
+ * - - EPERM: Operation not permitted/supported
+ */
+static inline int __attribute__((always_inline))
+rte_ring_peek(const struct rte_ring *r, void **obj_p)
+{
+ uint32_t cons_head, prod_tail;
+
+ if (r->cons.sc_dequeue) {
+ cons_head = r->cons.head;
+ prod_tail = r->prod.tail;
+
+ if (prod_tail - cons_head == 0) {
+ return -ENOENT;
+ }
+ *obj_p = r->ring[cons_head & r->prod.mask];
+ } else {
+ return -EPERM;
+ }
+ return 0;
+}
+
+/**
--------^_^--------
Best Regards
Yan Limin
