Add light events

libctru/include/3ds/synchronization.h

@@ -11,6 +11,13 @@ typedef _LOCK_T LightLock;
 /// A recursive lock.
 typedef _LOCK_RECURSIVE_T RecursiveLock;
 
+/// A light event.
+typedef struct
+{
+	s32 state;      ///< State of the event: -2=cleared sticky, -1=cleared oneshot, 0=signaled oneshot, 1=signaled sticky
+	LightLock lock; ///< Lock used for sticky timer operation
+} LightEvent;
+
 /// Performs a Data Synchronization Barrier operation.
 static inline void __dsb(void)
 {
@@ -114,3 +121,41 @@ int RecursiveLock_TryLock(RecursiveLock* lock);
  * @param lock Pointer to the lock.
  */
 void RecursiveLock_Unlock(RecursiveLock* lock);
+
+/**
+ * @brief Initializes a light event.
+ * @param event Pointer to the event.
+ * @param reset_type Type of reset the event uses (RESET_ONESHOT/RESET_STICKY).
+ */
+void LightEvent_Init(LightEvent* event, ResetType reset_type);
+
+/**
+ * @brief Clears a light event.
+ * @param event Pointer to the event.
+ */
+void LightEvent_Clear(LightEvent* event);
+
+/**
+ * @brief Wakes up threads waiting on a sticky light event without signaling it. If the event had been signaled before, it is cleared instead.
+ * @param event Pointer to the event.
+ */
+void LightEvent_Pulse(LightEvent* event);
+
+/**
+ * @brief Signals a light event, waking up threads waiting on it.
+ * @param event Pointer to the event.
+ */
+void LightEvent_Signal(LightEvent* event);
+
+/**
+ * @brief Attempts to wait on a light event.
+ * @param event Pointer to the event.
+ * @return Non-zero if the event was signaled, zero otherwise.
+ */
+int LightEvent_TryWait(LightEvent* event);
+
+/**
+ * @brief Waits on a light event.
+ * @param event Pointer to the event.
+ */
+void LightEvent_Wait(LightEvent* event);

libctru/source/synchronization.c

@@ -127,3 +127,92 @@ void RecursiveLock_Unlock(RecursiveLock* lock)
 		LightLock_Unlock(&lock->lock);
 	}
 }
+
+static inline void LightEvent_SetState(LightEvent* event, int state)
+{
+	do
+		__ldrex(&event->state);
+	while (__strex(&event->state, state));
+}
+
+static inline int LightEvent_TryReset(LightEvent* event)
+{
+	do
+	{
+		if (__ldrex(&event->state))
+		{
+			__clrex();
+			return 0;
+		}
+	} while (__strex(&event->state, -1));
+	return 1;
+}
+
+void LightEvent_Init(LightEvent* event, ResetType reset_type)
+{
+	LightLock_Init(&event->lock);
+	LightEvent_SetState(event, reset_type == RESET_STICKY ? -2 : -1);
+}
+
+void LightEvent_Clear(LightEvent* event)
+{
+	if (event->state == 1)
+	{
+		LightLock_Lock(&event->lock);
+		LightEvent_SetState(event, -2);
+		LightLock_Unlock(&event->lock);
+	} else if (event->state == 0)
+		LightEvent_SetState(event, -1);
+}
+
+void LightEvent_Pulse(LightEvent* event)
+{
+	if (event->state == -2)
+		svcArbitrateAddress(arbiter, (u32)event, ARBITRATION_SIGNAL, -1, 0);
+	else if (event->state == -1)
+		svcArbitrateAddress(arbiter, (u32)event, ARBITRATION_SIGNAL, 1, 0);
+	else
+		LightEvent_Clear(event);
+}
+
+void LightEvent_Signal(LightEvent* event)
+{
+	if (event->state == -1)
+	{
+		LightEvent_SetState(event, 0);
+		svcArbitrateAddress(arbiter, (u32)event, ARBITRATION_SIGNAL, 1, 0);
+	} else if (event->state == -2)
+	{
+		LightLock_Lock(&event->lock);
+		LightEvent_SetState(event, 1);
+		svcArbitrateAddress(arbiter, (u32)event, ARBITRATION_SIGNAL, -1, 0);
+		LightLock_Unlock(&event->lock);
+	}
+}
+
+int LightEvent_TryWait(LightEvent* event)
+{
+	if (event->state == 1)
+		return 1;
+	return LightEvent_TryReset(event);
+}
+
+void LightEvent_Wait(LightEvent* event)
+{
+	for (;;)
+	{
+		if (event->state == -2)
+		{
+			svcArbitrateAddress(arbiter, (u32)event, ARBITRATION_WAIT_IF_LESS_THAN, 0, 0);
+			return;
+		}
+		if (event->state != -1)
+		{
+			if (event->state == 1)
+				return;
+			if (event->state == 0 && LightEvent_TryReset(event))
+				return;
+		}
+		svcArbitrateAddress(arbiter, (u32)event, ARBITRATION_WAIT_IF_LESS_THAN, 0, 0);
+	}
+}