DragonFly On-Line Manual Pages

CK_RING_DEQUEUE_SPMC(3)                     DragonFly Library Functions Manual

NAME
     ck_ring_dequeue_spmc - dequeue pointer from bounded FIFO

LIBRARY
     Concurrency Kit (libck, -lck)

SYNOPSIS
     #include <ck_ring.h>

     bool
     ck_ring_dequeue_spmc(ck_ring_t *ring, ck_ring_buffer_t *buffer,
         void *result);

DESCRIPTION
     The ck_ring_dequeue_spmc(3) function dequeues a pointer from the bounded
     buffer pointed to by ring in FIFO fashion. The pointer is stored in the
     pointer pointed to by result.  The buffer pointed to by buffer must be
     unique to ring.  The decoupling of the ring from the buffer serves to
     address use-cases involving multiple address spaces and DMA, among
     others.  If you are on non-POSIX platforms or wish for strict compliance
     with C, then it is recommended to pass a pointer of type void ** for
     result.  This function is safe to call without locking for UINT_MAX
     concurrent invocations of ck_ring_dequeue_spmc(3) or
     ck_ring_trydequeue_spmc(3) and up to one concurrent
     ck_ring_enqueue_spmc(3) or ck_ring_tryenqueue_spmc(3) invocation. This
     function provides lock-free progress guarantees.

EXAMPLE
           #include <ck_ring.h>

           /* This ring was previously initialized with ck_ring_init. */
           ck_ring_t ring;

           /* The ring was initialized for 1023 elements. */
           ck_ring_buffer_t buffer[1024];

           void
           dequeue(void)
           {
                   void *result;

                   /* Dequeue from ring until it is empty. */
                   while (ck_ring_dequeue_spmc(&ring, &buffer, &result) == true) {
                           /*
                            * Results contains the oldest pointer in ring
                            * since the dequeue operation returned true.
                            */
                           operation(result);
                   }

                   /* An empty ring was encountered, leave. */
                   return;
           }

RETURN VALUES
     The function returns true if the buffer was non-empty.  The result of the
     dequeue operation is stored in the value pointed to by result.  The
     function will return false if the buffer was empty and the value in
     result will be undefined.

SEE ALSO
     ck_ring_init(3), ck_ring_trydequeue_spmc(3), ck_ring_enqueue_spmc(3),
     ck_ring_enqueue_spmc_size(3), ck_ring_dequeue_spsc(3),
     ck_ring_enqueue_spsc(3), ck_ring_enqueue_spsc_size(3),
     ck_ring_capacity(3), ck_ring_size(3)

     Additional information available at http://concurrencykit.org/

                                April 20, 2013