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VILLASnode/include/villas/queue.h

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/** Lock-free Multiple-Producer Multiple-consumer (MPMC) queue.
*
* Based on Dmitry Vyukov#s Bounded MPMC queue:
* http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
*
* @author Steffen Vogel <post@steffenvogel.de>
* @copyright 2017 Steffen Vogel
* @license BSD 2-Clause License
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modiffication, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*********************************************************************************/
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#pragma once
#include <stddef.h>
#include <stdint.h>
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#include <unistd.h>
#include "atomic.h"
#include "common.h"
/* Forward declarations */
struct memtype;
#define CACHELINE_SIZE 64
typedef char cacheline_pad_t[CACHELINE_SIZE];
struct queue_cell {
atomic_size_t sequence;
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off_t data_off; /**< Pointer relative to the queue struct */
};
/** A lock-free multiple-producer, multiple-consumer (MPMC) queue. */
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struct queue {
cacheline_pad_t _pad0; /**< Shared area: all threads read */
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atomic_state state;
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struct memtype *mem;
size_t buffer_mask;
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off_t buffer_off; /**< Relative pointer to struct queue_cell[] */
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cacheline_pad_t _pad1; /**< Producer area: only producers read & write */
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atomic_size_t tail; /**< Queue tail pointer */
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cacheline_pad_t _pad2; /**< Consumer area: only consumers read & write */
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atomic_size_t head; /**< Queue head pointer */
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cacheline_pad_t _pad3; /**< @todo Why needed? */
};
/** Initialize MPMC queue */
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int queue_init(struct queue *q, size_t size, struct memtype *mem);
/** Desroy MPMC queue and release memory */
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int queue_destroy(struct queue *q);
/** Return estimation of current queue usage.
*
* Note: This is only an estimation and not accurate as long other
* threads are performing operations.
*/
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size_t queue_available(struct queue *q);
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int queue_push(struct queue *q, void *ptr);
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int queue_pull(struct queue *q, void **ptr);
/** Enqueue up to \p cnt pointers of the \p ptr array into the queue.
*
* @return The number of pointers actually enqueued.
* This number can be smaller then \p cnt in case the queue is filled.
*/
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int queue_push_many(struct queue *q, void *ptr[], size_t cnt);
/** Dequeue up to \p cnt pointers from the queue and place them into the \p ptr array.
*
* @return The number of pointers actually dequeued.
* This number can be smaller than \p cnt in case the queue contained less than
* \p cnt elements.
*/
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int queue_pull_many(struct queue *q, void *ptr[], size_t cnt);
/** Closes the queue, causing following writes to fail and following reads (after
* the queue is empty) to fail.
*
* @return 0 on success.
* @return -1 on failure.
*/
int queue_close(struct queue *q);