VILLASnode/common/include/villas/task.hpp

/* Run tasks periodically.
 *
 * Author: Steffen Vogel <post@steffenvogel.de>
 * SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
 * SPDX-License-Identifier: Apache-2.0
 */

#pragma once

#include <cstdint>
#include <cstdio>

#include <ctime>

// We can choose between two periodic task implementations
//#define PERIODIC_TASK_IMPL NANOSLEEP
#define TIMERFD 1
#define CLOCK_NANOSLEEP 2
#define NANOSLEEP 3
#define RDTSC 4

#if defined(__MACH__)
#define PERIODIC_TASK_IMPL NANOSLEEP
#elif defined(__linux__)
#define PERIODIC_TASK_IMPL TIMERFD
#else
#error "Platform not supported"
#endif

#if PERIODIC_TASK_IMPL == RDTSC
#include <villas/tsc.hpp>
#endif

struct Task {
  int clock; // CLOCK_{MONOTONIC,REALTIME}

#if PERIODIC_TASK_IMPL == RDTSC // We use cycle counts in RDTSC mode
  uint64_t period;
  uint64_t next;
#else
  struct timespec period; // The period of periodic invations of this task
  struct timespec next;   // The timer value for the next invocation
#endif

#if PERIODIC_TASK_IMPL == TIMERFD
  int fd; // The timerfd_create(2) file descriptior.
#elif PERIODIC_TASK_IMPL == RDTSC
  struct Tsc tsc; // Initialized by tsc_init().
#endif

  // Create a new task with the given rate.
  Task(int clock = CLOCK_REALTIME);

  ~Task();

  // Wait until task elapsed
  //
  // @retval 0 An error occured. Maybe the task was stopped.
  // @retval >0 The nummer of runs this task already fired.
  uint64_t wait();

  void setNext(const struct timespec *next);
  void setTimeout(double to);
  void setRate(double rate);

  void stop();

  // Returns a poll'able file descriptor which becomes readable when the timer expires.
  //
  // Note: currently not supported on all platforms.
  int getFD() const;
};