Man page - ck_ring_trydequeue_spmc(3)

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Manual

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/ April 20, 2013 CK_RING_TRYDEQUEUE_SPMC (3)