以前没学过c++，最近开始在看android的代码，代码如下，这个thread中有个do while循环，这个循环是不是一直在进行啊？正常sensor轮询读取数据应该不用这么快吧？
bool SensorService::threadLoop()
{
LOGD("nuSensorService thread starting...");
const size_t numEventMax = 16 * (1 + mVirtualSensorList.size());
sensors_event_t buffer[numEventMax];
sensors_event_t scratch[numEventMax];
SensorDevice& device(SensorDevice::getInstance());
const size_t vcount = mVirtualSensorList.size();
ssize_t count;
do {
count = device.poll(buffer, numEventMax);
if (count<0) {
LOGE("sensor poll failed (%s)", strerror(-count));
break;
}
recordLastValue(buffer, count);
// handle virtual sensors
if (count && vcount) {
const DefaultKeyedVector<int, SensorInterface*> virtualSensors(
getActiveVirtualSensors());
const size_t activeVirtualSensorCount = virtualSensors.size();
if (activeVirtualSensorCount) {
size_t k = 0;
for (size_t i=0 ; i<size_t(count) ; i++) {
sensors_event_t const * const event = buffer;
for (size_t j=0 ; j<activeVirtualSensorCount ; j++) {
sensors_event_t out;
if (virtualSensors.valueAt(j)->process(&out, event[i])) {
buffer[count + k] = out;
k++;
}
}
}
if (k) {
// record the last synthesized values
recordLastValue(&buffer[count], k);
count += k;
// sort the buffer by time-stamps
sortEventBuffer(buffer, count);
}
}
}
// send our events to clients...
const SortedVector< wp<SensorEventConnection> > activeConnections(
getActiveConnections());
size_t numConnections = activeConnections.size();
for (size_t i=0 ; i<numConnections ; i++) {
sp<SensorEventConnection> connection(
activeConnections[i].promote());
if (connection != 0) {
connection->sendEvents(buffer, count, scratch);
}
}
} while (count >= 0 || Thread::exitPending());
LOGW("Exiting SensorService::threadLoop!");
return false;
} |
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