/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef threading_ConditionVariable_h
#define threading_ConditionVariable_h

#include "mozilla/Attributes.h"
#include "mozilla/Move.h"
#include "mozilla/TimeStamp.h"

#include <stdint.h>
#ifndef XP_WIN
# include <pthread.h>
#endif

#include "threading/LockGuard.h"
#include "threading/Mutex.h"

namespace js {

template <typename T> using UniqueLock = LockGuard<T>;

enum class CVStatus {
  NoTimeout,
  Timeout
};

// A poly-fill for std::condition_variable.
class ConditionVariable
{
public:
  struct PlatformData;

  ConditionVariable();
  ~ConditionVariable();

  // Wake one thread that is waiting on this condition.
  void notify_one();

  // Wake all threads that are waiting on this condition.
  void notify_all();

  // Block the current thread of execution until this condition variable is
  // woken from another thread via notify_one or notify_all.
  void wait(UniqueLock<Mutex>& lock);

  // As with |wait|, block the current thread of execution until woken from
  // another thread. This method will resume waiting once woken until the given
  // Predicate |pred| evaluates to true.
  template <typename Predicate>
  void wait(UniqueLock<Mutex>& lock, Predicate pred) {
    while (!pred()) {
      wait(lock);
    }
  }

  // Block the current thread of execution until woken from another thread, or
  // the given absolute time is reached. The given absolute time is evaluated
  // when this method is called, so will wake up after (abs_time - now),
  // independent of system clock changes. While insulated from clock changes,
  // this API is succeptible to the issues discussed above wait_for.
  CVStatus wait_until(UniqueLock<Mutex>& lock,
                      const mozilla::TimeStamp& abs_time);

  // As with |wait_until|, block the current thread of execution until woken
  // from another thread, or the given absolute time is reached. This method
  // will resume waiting once woken until the given Predicate |pred| evaluates
  // to true.
  template <typename Predicate>
  bool wait_until(UniqueLock<Mutex>& lock, const mozilla::TimeStamp& abs_time,
                  Predicate pred) {
    while (!pred()) {
      if (wait_until(lock, abs_time) == CVStatus::Timeout) {
        return pred();
      }
    }
    return true;
  }

  // Block the current thread of execution until woken from another thread, or
  // the given time duration has elapsed. Given that the system may be
  // interrupted between the callee and the actual wait beginning, this call
  // has a minimum granularity of the system's scheduling interval, and may
  // encounter substantially longer delays, depending on system load.
  CVStatus wait_for(UniqueLock<Mutex>& lock,
                    const mozilla::TimeDuration& rel_time);

  // As with |wait_for|, block the current thread of execution until woken from
  // another thread or the given time duration has elapsed. This method will
  // resume waiting once woken until the given Predicate |pred| evaluates to
  // true.
  template <typename Predicate>
  bool wait_for(UniqueLock<Mutex>& lock, const mozilla::TimeDuration& rel_time,
                Predicate pred) {
    return wait_until(lock, mozilla::TimeStamp::Now() + rel_time,
                      mozilla::Move(pred));
  }


private:
  ConditionVariable(const ConditionVariable&) = delete;
  ConditionVariable& operator=(const ConditionVariable&) = delete;

  PlatformData* platformData();

#ifndef XP_WIN
  void* platformData_[sizeof(pthread_cond_t) / sizeof(void*)];
  static_assert(sizeof(pthread_cond_t) / sizeof(void*) != 0 &&
                sizeof(pthread_cond_t) % sizeof(void*) == 0,
                "pthread_cond_t must have pointer alignment");
#else
  void* platformData_[4];
#endif
};

} // namespace js

#endif // threading_ConditionVariable_h