Revert "mobile/sensor: block until timeout occurs"

If the looper is waking up, the current timeout limit is exceeded.
There are no external APIs to query if a looper is trying to wake up
or blocking to wait for the event data. Therefore, I'm this
change and will replace the timeout with a significantly high number
that could only be exceeded if sensor fails with a fatal problem.
The goal is not to wait on ALooper_pollAll forever.

This reverts commit 1575a42f33e3354db87760bcc8c9d951e35347dd.

Change-Id: I861d81f2550c4435247a0b1d4ce141e94d1e3ec9
Reviewed-on: https://go-review.googlesource.com/8565
Reviewed-by: Burcu Dogan <jbd@google.com>

sensor/sensor_android.go

@@ -62,7 +62,6 @@ type inOut struct {
 type manager struct {
 	m     *C.android_SensorManager
 	inout chan inOut
-	minDelay int64 // read timeout in milliseconds
 }
 
 // initialize inits the manager and creates a goroutine to proxy the CGO calls.
@@ -115,9 +114,6 @@ func (m *manager) initialize() {
 
 func (m *manager) enable(t Type, delay time.Duration) error {
 	var err error
-	if d := delay.Nanoseconds() * 1000 * 1000; m.minDelay == 0 || d < m.minDelay {
-		m.minDelay = d
-	}
 	done := make(chan struct{})
 	m.inout <- inOut{
 		in:  enableSignal{t: t, delay: delay, err: &err},
@@ -152,10 +148,10 @@ func readEvents(m *manager, e []Event) (n int, err error) {
 	types := make([]C.int32_t, num)
 	timestamps := make([]C.int64_t, num)
 	vectors := make([]C.float, 3*num)
+
+	// TODO(jbd): add timeout.
 	n = int(C.android_readQueue(
-		m.m.looperId,
-		m.m.queue,
-		C.int(2*m.minDelay), // wait twice as much than the min-expected delay
+		m.m.looperId, m.m.queue,
 		C.int(num),
 		(*C.int32_t)(unsafe.Pointer(&types[0])),
 		(*C.int64_t)(unsafe.Pointer(&timestamps[0])),

sensor/sensors_android.c

@@ -39,38 +39,27 @@ void android_disableSensor(ASensorEventQueue* q, int s) {
   ASensorEventQueue_disableSensor(q, sensor);
 }
 
-// TODO(jbd): Introduce a struct of type, timestamp and vectors.
-// CGO doesn't support union types, therefore we will not be able
-// to reuse ASensorEvent.
-int android_readQueue(
-  int looperId,
-  ASensorEventQueue* q,
-  int timeoutMillis,
-  int n,
-  int32_t* types,
-  int64_t* timestamps,
-  float* vectors
-) {
+int android_readQueue(int looperId, ASensorEventQueue* q, int n, int32_t* types, int64_t* timestamps, float* vectors) {
   int id;
   int events;
   ASensorEvent event;
-  int i = 0, num = 0;
-  // TODO(jbd): Make sure we don't have to consume the sensor queue entirely.
-  while (i < n && (id = ALooper_pollAll(timeoutMillis, NULL, &events, NULL)) >= 0) {
+  // TODO(jbd): Timeout if pollAll blocks longer than it should.
+  int i = 0;
+  // Block forever until new events are on the queue.
+  while (i < n && (id = ALooper_pollAll(-1, NULL, &events, NULL)) >= 0) {
     if (id != looperId) {
       continue;
     }
     if (ASensorEventQueue_getEvents(q, &event, 1)) {
-      types[num] = event.type;
-      timestamps[num] = event.timestamp;
-      vectors[num*3] = event.vector.x;
-      vectors[num*3+1] = event.vector.y;
-      vectors[num*3+2] = event.vector.z;
-      num++;
-    }
+      types[i] = event.type;
+      timestamps[i] = event.timestamp;
+      vectors[i*3] = event.vector.x;
+      vectors[i*3+1] = event.vector.y;
+      vectors[i*3+2] = event.vector.z;
       i++;
     }
-  return num;
+  }
+  return i;
 }
 
 void android_destroyManager(android_SensorManager* m) {

sensor/sensors_android.h

@@ -15,12 +15,6 @@ void android_createManager(int looperId, android_SensorManager* dst);
 void android_destroyManager(android_SensorManager* m);
 int  android_enableSensor(ASensorEventQueue*, int, int32_t);
 void android_disableSensor(ASensorEventQueue*, int);
-int  android_readQueue(
-  int looperId, ASensorEventQueue* q,
-  int timeoutMillis, int n,
-  int32_t* types,
-  int64_t* timestamps,
-  float* vectors
-);
+int  android_readQueue(int looperId, ASensorEventQueue* q, int n, int32_t* types, int64_t* timestamps, float* vectors);
 
 #endif