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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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
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