/*
 * Copyright (C) 2014 Max Kellermann <max@duempel.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, 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
 * FOUNDATION 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.
 */

#ifndef THREAD_UTIL_HXX
#define THREAD_UTIL_HXX

#if defined(__linux__) && !defined(ANDROID)
#include <sched.h>
#include <sys/syscall.h>
#include <unistd.h>
#elif defined(WIN32)
#include <windows.h>
#endif

#if defined(__linux__) && !defined(ANDROID)

static int
ioprio_set(int which, int who, int ioprio)
{
  return syscall(__NR_ioprio_set, which, who, ioprio);
}

static void
ioprio_set_idle()
{
  static constexpr int _IOPRIO_WHO_PROCESS = 1;
  static constexpr int _IOPRIO_CLASS_IDLE = 3;
  static constexpr int _IOPRIO_CLASS_SHIFT = 13;
  static constexpr int _IOPRIO_IDLE =
    (_IOPRIO_CLASS_IDLE << _IOPRIO_CLASS_SHIFT) | 7;

  ioprio_set(_IOPRIO_WHO_PROCESS, 0, _IOPRIO_IDLE);
}

#endif

/**
 * Lower the current thread's priority to "idle" (very low).
 */
static inline void
SetThreadIdlePriority()
{
#ifdef __linux__
#if defined(__BIONIC__) && !defined(SCHED_IDLE)
/* Bionic supports SCHED_IDLE() since API level 21, but we build with
   API level 8 */
#define SCHED_IDLE 5
#endif

#ifdef SCHED_IDLE
  static struct sched_param sched_param;
  sched_setscheduler(0, SCHED_IDLE, &sched_param);
#endif

#ifndef ANDROID
  /* this system call is forbidden via seccomp on Android 8 and leads
     to crash (SIGSYS) */
  ioprio_set_idle();
#endif

#elif defined(WIN32)
  SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_IDLE);
#endif
};

/**
 * Raise the current thread's priority to "real-time" (very high).
 */
static inline void
SetThreadRealtime()
{
#ifdef __linux__
  struct sched_param sched_param;
  sched_param.sched_priority = 50;

  int policy = SCHED_FIFO;
#ifdef SCHED_RESET_ON_FORK
  policy |= SCHED_RESET_ON_FORK;
#endif

  sched_setscheduler(0, policy, &sched_param);
#endif
};

#endif
