MainThreadNotifier.h [plain text]
#pragma once
#include <functional>
#include <wtf/Atomics.h>
#include <wtf/Lock.h>
#include <wtf/MainThread.h>
#include <wtf/RunLoop.h>
#include <wtf/ThreadSafeRefCounted.h>
namespace WebCore {
template <typename T>
class MainThreadNotifier final : public ThreadSafeRefCounted<MainThreadNotifier<T>> {
public:
static Ref<MainThreadNotifier> create()
{
return adoptRef(*new MainThreadNotifier());
}
~MainThreadNotifier()
{
ASSERT(!m_isValid.load());
}
bool isValid() const { return m_isValid.load(); }
template<typename F>
void notify(T notificationType, F&& callbackFunctor)
{
ASSERT(m_isValid.load());
ASSERT(!(static_cast<int>(notificationType) & (static_cast<int>(notificationType) - 1)));
if (isMainThread()) {
removePendingNotification(notificationType);
callbackFunctor();
return;
}
if (!addPendingNotification(notificationType))
return;
RunLoop::main().dispatch([this, protectedThis = makeRef(*this), notificationType, callback = WTF::Function<void()>(WTFMove(callbackFunctor))] {
if (!m_isValid.load())
return;
if (removePendingNotification(notificationType))
callback();
});
}
template<typename F>
void notifyAndWait(T notificationType, F&& callbackFunctor)
{
Lock mutex;
Condition condition;
notify(notificationType, [functor = WTFMove(callbackFunctor), &condition, &mutex] {
functor();
LockHolder holder(mutex);
condition.notifyOne();
});
if (!isMainThread()) {
LockHolder holder(mutex);
condition.wait(mutex);
}
}
void cancelPendingNotifications(unsigned mask = 0)
{
ASSERT(m_isValid.load());
LockHolder locker(m_pendingNotificationsLock);
if (mask)
m_pendingNotifications &= ~mask;
else
m_pendingNotifications = 0;
}
void invalidate()
{
ASSERT(m_isValid.load());
m_isValid.store(false);
}
private:
MainThreadNotifier()
{
m_isValid.store(true);
}
bool addPendingNotification(T notificationType)
{
LockHolder locker(m_pendingNotificationsLock);
if (notificationType & m_pendingNotifications)
return false;
m_pendingNotifications |= notificationType;
return true;
}
bool removePendingNotification(T notificationType)
{
LockHolder locker(m_pendingNotificationsLock);
if (notificationType & m_pendingNotifications) {
m_pendingNotifications &= ~notificationType;
return true;
}
return false;
}
Lock m_pendingNotificationsLock;
unsigned m_pendingNotifications { 0 };
Atomic<bool> m_isValid;
};
}