CK_RING_DEQUEUE_SPMC(3) BSD Library Functions Manual CK_RING_DEQUEUE_SPMC(3)NAMEck_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 oth‐
ers. 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 con‐
current 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 func‐
tion will return false if the buffer was empty and the value in result
will be undefined.
SEE ALSOck_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
