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/*
* Copyright 2004 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef RTC_BASE_EVENT_H_
#define RTC_BASE_EVENT_H_
#include "api/units/time_delta.h"
#if defined(WEBRTC_WIN)
#include <windows.h>
#elif defined(WEBRTC_POSIX)
#include <pthread.h>
#else
#error "Must define either WEBRTC_WIN or WEBRTC_POSIX."
#endif
#include "rtc_base/synchronization/yield_policy.h"
namespace webrtc {
// RTC_DISALLOW_WAIT() utility
//
// Sets a stack-scoped flag that disallows use of `Event::Wait` by means
// of raising a DCHECK when a call to `Event::Wait()` is made..
// This is useful to guard synchronization-free scopes against regressions.
//
// Example of what this would catch (`ScopeToProtect` calls `Foo`):
//
// void Foo(TaskQueue* tq) {
// Event event;
// tq->PostTask([&event]() {
// event.Set();
// });
// event.Wait(Event::kForever); // <- Will trigger a DCHECK.
// }
//
// void ScopeToProtect() {
// TaskQueue* tq = GetSomeTaskQueue();
// RTC_DISALLOW_WAIT(); // Policy takes effect.
// Foo(tq);
// }
//
#if RTC_DCHECK_IS_ON
#define RTC_DISALLOW_WAIT() ScopedDisallowWait disallow_wait_##__LINE__
#else
#define RTC_DISALLOW_WAIT()
#endif
class Event {
public:
// TODO(bugs.webrtc.org/14366): Consider removing this redundant alias.
static constexpr TimeDelta kForever = TimeDelta::PlusInfinity();
static constexpr TimeDelta kDefaultWarnDuration = TimeDelta::Seconds(3);
Event();
Event(bool manual_reset, bool initially_signaled);
Event(const Event&) = delete;
Event& operator=(const Event&) = delete;
~Event();
void Set();
void Reset();
// Waits for the event to become signaled, but logs a warning if it takes more
// than `warn_after`, and gives up completely if it takes more than
// `give_up_after`. (If `warn_after >= give_up_after`, no warning will be
// logged.) Either or both may be `kForever`, which means wait indefinitely.
//
// Care is taken so that the underlying OS wait call isn't requested to sleep
// shorter than `give_up_after`.
//
// Returns true if the event was signaled, false if there was a timeout or
// some other error.
bool Wait(TimeDelta give_up_after, TimeDelta warn_after);
// Waits with the given timeout and a reasonable default warning timeout.
bool Wait(TimeDelta give_up_after) {
return Wait(give_up_after, give_up_after.IsPlusInfinity()
? kDefaultWarnDuration
: kForever);
}
private:
#if defined(WEBRTC_WIN)
HANDLE event_handle_;
#elif defined(WEBRTC_POSIX)
pthread_mutex_t event_mutex_;
pthread_cond_t event_cond_;
const bool is_manual_reset_;
bool event_status_;
#endif
};
// These classes are provided for compatibility with Chromium.
// The Event implementation is overriden inside of Chromium for the
// purposes of detecting when threads are blocked that shouldn't be as well as
// to use the more accurate event implementation that's there than is provided
// by default on some platforms (e.g. Windows).
// When building with standalone WebRTC, this class is a noop.
// For further information, please see the
// ScopedAllowBaseSyncPrimitives(ForTesting) classes in Chromium.
class ScopedAllowBaseSyncPrimitives {
public:
ScopedAllowBaseSyncPrimitives() {}
~ScopedAllowBaseSyncPrimitives() {}
};
class ScopedAllowBaseSyncPrimitivesForTesting {
public:
ScopedAllowBaseSyncPrimitivesForTesting() {}
~ScopedAllowBaseSyncPrimitivesForTesting() {}
};
#if RTC_DCHECK_IS_ON
class ScopedDisallowWait {
public:
ScopedDisallowWait() = default;
private:
class DisallowYieldHandler : public YieldInterface {
public:
void YieldExecution() override { RTC_DCHECK_NOTREACHED(); }
} handler_;
ScopedYieldPolicy policy{&handler_};
};
#endif
} // namespace webrtc
// Re-export symbols from the webrtc namespace for backwards compatibility.
// TODO(bugs.webrtc.org/4222596): Remove once all references are updated.
#ifdef WEBRTC_ALLOW_DEPRECATED_NAMESPACES
namespace rtc {
using ::webrtc::Event;
using ::webrtc::ScopedAllowBaseSyncPrimitives;
using ::webrtc::ScopedAllowBaseSyncPrimitivesForTesting;
} // namespace rtc
#endif // WEBRTC_ALLOW_DEPRECATED_NAMESPACES
#endif // RTC_BASE_EVENT_H_
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