NAME¶
ck_ring_trydequeue_spmc
—
dequeue from bounded FIFO and allow for spurious
failure
LIBRARY¶
Concurrency Kit (libck, -lck)
SYNOPSIS¶
#include
<ck_ring.h>
bool
ck_ring_trydequeue_spmc
(
ck_ring_t
*ring,
ck_ring_buffer_t
*buffer,
void
*result);
DESCRIPTION¶
The
ck_ring_trydequeue_spmc
(
3)
function attempts to dequeue 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 and point to an array of
ck_ring_buffer_t of sufficient length (according to the power-of-2 elements in
the buffer). 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
ck_ring_dequeue_spmc
(
3)
or
ck_ring_trydequeue_spmc
(
3)
invocations and up to one concurrent
ck_ring_enqueue_spmc
(
3)
or
ck_ring_tryenqueue_spmc
(
3)
invocation. This operation will always complete in a bounded number of steps.
It is possible for the function to return false even if
ring is non-empty. This
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 contention is actively observed. */
while (ck_ring_trydequeue_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 dequeue operation completely successfully in a
bounded number of steps. The result of the dequeue operation is stored in the
value pointed to by
result. Otherwise, the
function will return false if the buffer was empty or if the operation could
not be completed in a bounded number of steps. If the function returns false,
then the contents of
result are undefined.
SEE ALSO¶
ck_ring_init(3),
ck_ring_dequeue_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/