VILLASnode/include/villas/queue_signalled.h

/* Wrapper around queue that uses POSIX CV's for signalling writes.
 *
 * Author: Georg Martin Reinke <georg.reinke@rwth-aachen.de>
 * SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
 * SPDX-License-Identifier: Apache-2.0
 */

#pragma once

#include <pthread.h>

#include <villas/node/config.hpp>
#include <villas/queue.h>

namespace villas {
namespace node {

enum class QueueSignalledMode {
  AUTO, // We will choose the best method available on the platform
  PTHREAD,
  POLLING,
#ifdef HAS_EVENTFD
  EVENTFD,

#endif
};

enum class QueueSignalledFlags { PROCESS_SHARED = (1 << 4) };

// Wrapper around queue that uses POSIX CV's for signalling writes.
struct CQueueSignalled {
  struct CQueue queue; // Actual underlying queue.

  enum QueueSignalledMode mode;
  enum QueueSignalledFlags flags;

  union {
    struct {
      pthread_cond_t ready; // Condition variable to signal writes to the queue.
      pthread_mutex_t mutex; // Mutex for ready.
    } pthread;
#ifdef __linux__
    int eventfd;
#endif
  };
};

#define queue_signalled_available(q) queue_available(&((q)->queue))

int queue_signalled_init(
    struct CQueueSignalled *qs, size_t size = DEFAULT_QUEUE_LENGTH,
    struct memory::Type *mem = memory::default_type,
    enum QueueSignalledMode mode = QueueSignalledMode::AUTO, int flags = 0)
    __attribute__((warn_unused_result));

int queue_signalled_destroy(struct CQueueSignalled *qs)
    __attribute__((warn_unused_result));

int queue_signalled_push(struct CQueueSignalled *qs, void *ptr)
    __attribute__((warn_unused_result));

int queue_signalled_pull(struct CQueueSignalled *qs, void **ptr)
    __attribute__((warn_unused_result));

int queue_signalled_push_many(struct CQueueSignalled *qs, void *ptr[],
                              size_t cnt) __attribute__((warn_unused_result));

int queue_signalled_pull_many(struct CQueueSignalled *qs, void *ptr[],
                              size_t cnt) __attribute__((warn_unused_result));

int queue_signalled_close(struct CQueueSignalled *qs)
    __attribute__((warn_unused_result));

// Returns a file descriptor which can be used with poll / select to wait for new data
int queue_signalled_fd(struct CQueueSignalled *qs);

} // namespace node
} // namespace villas