NAME

ck_ring_enqueue_spsc_size — enqueue pointer into bounded FIFO and return size of buffer

LIBRARY

Concurrency Kit (libck, -lck)

SYNOPSIS

#include <ck_ring.h>

bool
ck_ring_enqueue_spsc_size(ck_ring_t *ring, ck_ring_buffer_t *buffer, void *entry, unsigned int *size);

DESCRIPTION

The ck_ring_enqueue_spsc_size(3) function enqueues the pointer entry into the bounded buffer pointed to by ring in FIFO fashion. 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 entry. This function is safe to call without locking for up to one concurrent invocation of ck_ring_dequeue_spsc(3). This function provides wait-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
enqueue(void)
{
	void *entry = some_object;
	unsigned int length;

	/* Attempt to enqueue pointer to some_object into buffer. */
	if (ck_ring_enqueue_spsc(&ring, &buffer, &entry, &length) == false) {
		/*
		 * The buffer was full and the enqueue operation
		 * has failed.
		 */
		return;
	}

	/*
	 * If buffer length was 100 items or more at the time entry was
	 * enqueued, do something.
	 */
	if (length > 100) {
		do_something;
	}

	return;
}

RETURN VALUES

The function returns true if the value of entry was successfully enqueued into ring. This function will return the number of items in ring with respect to the linearization point (the point in item that entry is enqueued). The function will return false if the value of entry could not be enqueued which only occurs if ring was full.