Sensor框架理解
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Sensor框架理解
在这个系列的文章我们只是为了讲清楚Sensor框架的设计和工作原理基于4.0,4.0以下的代码有所区别,尤其是2.2以下根本就没有Binder架构,不讲驱动,也不讲具体的某一个应用该怎么处理Sensor的数据。
一、整体的架构:
从这个图来看Sensor的架构还是非常的清淅,
黄色部分表示硬件,它要挂在I2C总线上
红色部分表示驱动,把驱动注册到Kernel的Input Subsystem上,然后通过Event Device把Sensor数据传到HAL层,准确说是HAL从Event读
绿色部分表示动态库,它封装了整个Sensor的IPC机制,如SensorManager是客户端,SensorService是服务端,而HAL部分是封装了服务端对Kernel的直接访问
蓝色部分就是我们的Framework和Application了,JNI负责访问Sensor的客户端,而Application就是具体的应用程序,用来接收Sensor返回的数据,并处理实现对应的UI效果,如屏幕旋转,打电话时灭屏,自动调接背光(这三个功能的具体实现会在以后分析)
相关代码:
从HAL到Framework:
Framework部分:
frameworks/base/core/java/android/hardware/SensorManager.java
frameworks/base/core/jni/android_hardware_sensorManager.cpp
下面的代码会生成到:libgui.so
frameworks/base/libs/gui/SensorManager.cpp
frameworks/base/libs/gui/SensorEventQueue.cpp
frameworks/base/libs/gui/SensorChannel.cpp
frameworks/base/libs/gui/Sensor.cpp
下面的代码会生成:libsensorservice.so
frameworks/base/services/sensorservice/SensorService.cpp
frameworks/base/services/sensorservice/SensorDevice.cpp
HAL部分:这部分代码最终会生成 sensor.default.so 到/system/lib/hw/
hardware/libhardware/include/hardware/Sensors.h
device/qcom/msm7627a/libsensors/Sensors.cpp
device/qcom/msm7627a/libsensors/SensorBase.h
device/qcom/msm7627a/libsensors/AccSensor.cpp
device/qcom/msm7627a/libsensors/ProximitySensor.cpp
device/qcom/msm7627a/libsensors/LightSensor.cpp
device/qcom/msm7627a/libsensors/TmdSensor.cpp
device/qcom/msm7627a/libsensors/MagnetoSensor.cpp
device/qcom/msm7627a/libsensors/GyroSensor.cpp
device/qcom/msm7627a/libsensors/InputEventRead.h
device/qcom/msm7627a/libsensors/InputEventRead.cpp
Drivers:
P-Sensor:
device/qcom/msm7627a/libsensors/Tmd2771.h
kernel/drivers/misc/Tmd2771.c
(从这个代码路径大家可以看出我用来分析的代码是高通7627a平台的,
和Google原生代码没什么差别,而MTK的代码差别就大了,从HAL层开始完全不一样。)
我们还是列一下Android一般有哪些Sensor吧!
AccelerometerSensor
MagneticSensor
OrientationSensor
ProximitySensor
LightSensor
Gyro
这是我们最常见手机上有的Sensor,不过一般低端手机是没有Gyro的,而A Sensor用的并不是三轴的而是两轴。
二、应用举例:
- SensorManager sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
- Sensor accSensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
- sensorManager.registerListener(this, accSensor, SensorManager.SENSOR_DELAY_NORMAL);
- sensorManager.unregisterListener(this, accSensor);
- //然后在当前Activity中实现以下的两个函数
- public void onSensorChanged(SensorEvent event)
- public void onAccuracyChanged(Sensor sensor, int accuracy)
SensorManager sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);Sensor accSensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);sensorManager.registerListener(this, accSensor, SensorManager.SENSOR_DELAY_NORMAL);sensorManager.unregisterListener(this, accSensor);//然后在当前Activity中实现以下的两个函数public void onSensorChanged(SensorEvent event) public void onAccuracyChanged(Sensor sensor, int accuracy)
三、SensorService
服务程序启动,它是由SystemManager启动起来的:
frameworks/base/cmds/system_server/library/system_init.cpp
- property_get("system_init.startsensorservice", propBuf, "1");
- if (strcmp(propBuf, "1") == 0) {
- // Start the sensor service
- SensorService::instantiate();
- }
property_get("system_init.startsensorservice", propBuf, "1"); if (strcmp(propBuf, "1") == 0) { // Start the sensor service SensorService::instantiate(); }整个C/S通信的架构图:
需要特别说明的是,BpSensorServer并没有在系统中被用到,如果你从ISensorServer.cpp中把它删除也不会对Sensor的工作有任何影响。
它的工作被SensorManager.cpp所取代,ServiceManager直接获取上面System_init文件中添加的SensorService对像。
四、创建SensorManager
1. new SensorManager
它有两个地方去创建这个Sensor client Object,一个就是ContextImpl,另一个就是PowerManagerService中,contextImpl大家都明白是为了应用程序很方便的获取Service,PowerManager中为什么要创建这个对象我们后面再分析。
2.natvieClassInit
它在SensorManager(JAVA)的构造函数中被调用,作用就是创建一个Sensor.java类的实例对象。
3.sensors_module_init()
它也是在SensorManager(JAVA)的构造函数中被调用的,它的作用就是初始华SensorManager(cpp)。
- static jint
- sensors_module_init(JNIEnv *env, jclass clazz)
- {
- SensorManager::getInstance();
- return 0;
- }
static jintsensors_module_init(JNIEnv *env, jclass clazz){ SensorManager::getInstance(); return 0;}通过getInstance()就可以知道它是一个单件类,实例的创建由其父类Singleton<SensorManager>,
SensorManager只需要在实现文件调用以下的代码:
ANDROID_SINGLETON_STATIC_INSTANCE(SensorManager)
接着是SensorManager(cpp)的构造函数也没有做什么就是通过ServiceManager获取了SensorService的实例对象。
4. onFirstRef的实例
其实SensorService在添加实例到ServiceManager的时候就已经实例化过后了,因为在Binder.c中就会保存对它的引用,而RefBase的意思就是用来管理对像的引用,所以它会在对象第一次被引用的时候就调用onFirstRef。
接下来我们看看SensorService::onFirstRef里面做了哪些工作。
5. 创建SensorDevice
SensorDevice的构造函数:
- status_t err = hw_get_module(SENSORS_HARDWARE_MODULE_ID,
- (hw_module_t const**)&mSensorModule);
status_t err = hw_get_module(SENSORS_HARDWARE_MODULE_ID, (hw_module_t const**)&mSensorModule);这句话的意思是JNI加载HAL的库文件,并创建SensorModle的对象,Sensor的库文件通常是sensor.default.so
上图接下来是sensors_open,这个函数并没有在SensorDevice中实现,而是调用的HAL层的函数,相关代码路径已在上面列出。
- static int open_sensors(const struct hw_module_t* module, const char* id,
- struct hw_device_t** device)
- {
- int status = -EINVAL;
- LOGE("%s %d => %s", __FILE__, __LINE__, __func__);
- sensors_poll_context_t *dev = new sensors_poll_context_t();
- memset(&dev->device, 0, sizeof(sensors_poll_device_t));
- dev->device.common.tag = HARDWARE_DEVICE_TAG;
- dev->device.common.version = 0;
- dev->device.common.module = const_cast<hw_module_t*>(module);
- dev->device.common.close = poll__close;
- dev->device.activate = poll__activate;
- dev->device.setDelay = poll__setDelay;
- dev->device.poll = poll__poll;
- *device = &dev->device.common;
- status = 0;
- return status;
- }
static int open_sensors(const struct hw_module_t* module, const char* id, struct hw_device_t** device){ int status = -EINVAL;LOGE("%s %d => %s", __FILE__, __LINE__, __func__); sensors_poll_context_t *dev = new sensors_poll_context_t(); memset(&dev->device, 0, sizeof(sensors_poll_device_t)); dev->device.common.tag = HARDWARE_DEVICE_TAG; dev->device.common.version = 0; dev->device.common.module = const_cast<hw_module_t*>(module); dev->device.common.close = poll__close; dev->device.activate = poll__activate; dev->device.setDelay = poll__setDelay; dev->device.poll = poll__poll; *device = &dev->device.common; status = 0; return status;}我们看new sensors_poll_device_t();
- sensors_poll_context_t::sensors_poll_context_t()
- {
- #ifdef TMD27713_SENSOR
- mSensors[tmd] = new TmdSensor();
- mPollFds[tmd].fd = mSensors[tmd]->getFd();
- mPollFds[tmd].events = POLLIN;
- mPollFds[tmd].revents = 0;
- #else
- mSensors[light] = new LightSensor();
- mPollFds[light].fd = mSensors[light]->getFd();
- mPollFds[light].events = POLLIN;
- #endif
- mSensors[acc] = new AccSensor();
- mPollFds[acc].fd = mSensors[acc]->getFd();
- mPollFds[acc].events = POLLIN;
- mPollFds[acc].revents = 0;
- mSensors[mag] = new MagnetoSensor((AccSensor*)mSensors[acc]);
- mPollFds[mag].fd = mSensors[mag]->getFd();
- mPollFds[mag].events = POLLIN;
- mPollFds[mag].revents = 0;
- int wakeFds[2];
- int result = pipe(wakeFds);
- fcntl(wakeFds[0], F_SETFL, O_NONBLOCK);
- fcntl(wakeFds[1], F_SETFL, O_NONBLOCK);
- mWritePipeFd = wakeFds[1];
- mPollFds[wake].fd = wakeFds[0];
- mPollFds[wake].events = POLLIN;
- mPollFds[wake].revents = 0;
- }
sensors_poll_context_t::sensors_poll_context_t(){#ifdef TMD27713_SENSOR mSensors[tmd] = new TmdSensor(); mPollFds[tmd].fd = mSensors[tmd]->getFd(); mPollFds[tmd].events = POLLIN; mPollFds[tmd].revents = 0;#else mSensors[light] = new LightSensor(); mPollFds[light].fd = mSensors[light]->getFd(); mPollFds[light].events = POLLIN;#endif mSensors[acc] = new AccSensor(); mPollFds[acc].fd = mSensors[acc]->getFd(); mPollFds[acc].events = POLLIN; mPollFds[acc].revents = 0; mSensors[mag] = new MagnetoSensor((AccSensor*)mSensors[acc]); mPollFds[mag].fd = mSensors[mag]->getFd(); mPollFds[mag].events = POLLIN; mPollFds[mag].revents = 0; int wakeFds[2]; int result = pipe(wakeFds); fcntl(wakeFds[0], F_SETFL, O_NONBLOCK); fcntl(wakeFds[1], F_SETFL, O_NONBLOCK); mWritePipeFd = wakeFds[1]; mPollFds[wake].fd = wakeFds[0]; mPollFds[wake].events = POLLIN; mPollFds[wake].revents = 0;}这部分代码就创建HAL和Kernel Event通信的类,还有Sensor数据读写管道的创建。
返回open_sensors再看剩下的代码,就是创建sensors_poll_device_t对象并把sensor控制的相关函数指针赋值给它。
6. SensorDevice 调用get_sensors_list
这个方法还是调用到了HAL中,而HAL中的这个函数也就是返回以下数组:
- /* The SENSORS Module */
- static const struct sensor_t sSensorList[] = {
- { "ST 3-axis Accelerometer",
- "STMicroelectronics",
- 1, SENSORS_ACCELERATION_HANDLE,
- SENSOR_TYPE_ACCELEROMETER, RANGE_A, CONVERT_A, 0.23f, 20000, { } },
- { "ST 3-axis Magnetic field sensor",
- "STMicroelectronics",
- 1, SENSORS_MAGNETIC_FIELD_HANDLE,
- SENSOR_TYPE_MAGNETIC_FIELD, 2000.0f, CONVERT_M, 6.8f, 16667, { } },
- { "iNemo Orientation sensor",
- "STMicroelectronics",
- 1, SENSORS_ORIENTATION_HANDLE,
- SENSOR_TYPE_ORIENTATION, 360.0f, CONVERT_O, 7.8f, 16667, { } },
- };
/* The SENSORS Module */static const struct sensor_t sSensorList[] = { { "ST 3-axis Accelerometer", "STMicroelectronics", 1, SENSORS_ACCELERATION_HANDLE, SENSOR_TYPE_ACCELEROMETER, RANGE_A, CONVERT_A, 0.23f, 20000, { } }, { "ST 3-axis Magnetic field sensor", "STMicroelectronics", 1, SENSORS_MAGNETIC_FIELD_HANDLE, SENSOR_TYPE_MAGNETIC_FIELD, 2000.0f, CONVERT_M, 6.8f, 16667, { } }, { "iNemo Orientation sensor", "STMicroelectronics", 1, SENSORS_ORIENTATION_HANDLE, SENSOR_TYPE_ORIENTATION, 360.0f, CONVERT_O, 7.8f, 16667, { } },};我们需要特别关组的是第4,5个参数,第4参数Handle是对kernel而言的,如激活,读写event,代码中的说明:
/* handle that identifies this sensors. This handle is used to activate
* and deactivate this sensor. The value of the handle must be 8 bits
* in this version of the API.
*/
而第五个参数是相对于上层代码而言。
7. mSensorDevice->activate
在获取到Sensor列表以后,我们就去激活每一个Sensor:
mSensorDevice->activate(mSensorDevice, list[i].handle, 0);
- int sensors_poll_context_t::activate(int handle, int enabled) {
- int index = handleToDriver(handle);
- if (index < 0) return index;
- LOGE("sensor.cpp:index = %d\t handle= %d\t en=%d",index,handle,enabled);//by zhangfeng
- int err = mSensors[index]->enable(handle, enabled);
- if (enabled && !err) {
- const char wakeMessage(WAKE_MESSAGE);
- int result = write(mWritePipeFd, &wakeMessage, 1);
- LOGE_IF(result<0, "error sending wake message (%s)", strerror(errno));
- }
- return err;
- }
int sensors_poll_context_t::activate(int handle, int enabled) { int index = handleToDriver(handle); if (index < 0) return index;LOGE("sensor.cpp:index = %d\t handle= %d\t en=%d",index,handle,enabled);//by zhangfeng int err = mSensors[index]->enable(handle, enabled); if (enabled && !err) { const char wakeMessage(WAKE_MESSAGE); int result = write(mWritePipeFd, &wakeMessage, 1); LOGE_IF(result<0, "error sending wake message (%s)", strerror(errno)); } return err;}这儿要介绍一下handleToDriver
- int handleToDriver(int handle) const {
- switch (handle) {
- case ID_A:
- return acc;
- case ID_M:
- case ID_O:
- return mag;
- #ifdef TMD27713_SENSOR
- case ID_P:
- case ID_L:
- return tmd;
- #else
- case ID_P:
- return proximity;
- case ID_L:
- return light;
- #endif
- case ID_GY:
- return gyro;
- }
- return -EINVAL;
- }
int handleToDriver(int handle) const { switch (handle) { case ID_A: return acc; case ID_M: case ID_O: return mag;#ifdef TMD27713_SENSOR case ID_P: case ID_L:return tmd;#elsecase ID_P: return proximity;case ID_L:return light;#endifcase ID_GY:return gyro; } return -EINVAL; }传进来的就是我们上面说的第4个参数Handle,返回的是对应的和kernel交互的类的数组下标(Sensors[acc])下标。
从上面的sensors_poll_context_t()中sensors[]的定义我们可以找到Sensors[acc]对应的值为AccSensor。
mSensors[index]->enable(handle,enabled)目的就是打开这个Sensor,里面如何打开的?linux上面不是一切兼为文件吗?就是打开对应的驱动文件嘛,所以里面的东西我们就不看了,HAL我们只分析到Sensors.cpp。
8. 扩展Sensor list
好SensorDevice里面的初始化代码走完了,回到SensorService。
- void SensorService::onFirstRef()
- {
- LOGD("nuSensorService starting...");
- SensorDevice& dev(SensorDevice::getInstance());
- ....
- if (hasGyro) {
- // Always instantiate Android's virtual sensors. Since they are
- // instantiated behind sensors from the HAL, they won't
- // interfere with applications, unless they looks specifically
- // for them (by name).
- registerVirtualSensor( new RotationVectorSensor() );
- registerVirtualSensor( new GravitySensor(list, count) );
- registerVirtualSensor( new LinearAccelerationSensor(list, count) );
- // these are optional
- registerVirtualSensor( new OrientationSensor() );
- registerVirtualSensor( new CorrectedGyroSensor(list, count) );
- // virtual debugging sensors...
- char value[PROPERTY_VALUE_MAX];
- property_get("debug.sensors", value, "0");
- if (atoi(value)) {
- registerVirtualSensor( new GyroDriftSensor() );
- }
- }
void SensorService::onFirstRef(){ LOGD("nuSensorService starting..."); SensorDevice& dev(SensorDevice::getInstance());.... if (hasGyro) { // Always instantiate Android's virtual sensors. Since they are // instantiated behind sensors from the HAL, they won't // interfere with applications, unless they looks specifically // for them (by name). registerVirtualSensor( new RotationVectorSensor() ); registerVirtualSensor( new GravitySensor(list, count) ); registerVirtualSensor( new LinearAccelerationSensor(list, count) ); // these are optional registerVirtualSensor( new OrientationSensor() ); registerVirtualSensor( new CorrectedGyroSensor(list, count) ); // virtual debugging sensors... char value[PROPERTY_VALUE_MAX]; property_get("debug.sensors", value, "0"); if (atoi(value)) { registerVirtualSensor( new GyroDriftSensor() ); } }
- ......
......
- run("SensorService", PRIORITY_URGENT_DISPLAY);
run("SensorService", PRIORITY_URGENT_DISPLAY);}省去了很多的代码,从上面的代码可以看出如果有Gyro在Sensor List中,那么它就会注册RotationVector,Gravity,LinearAcceleration,Orientation,CorrectedGyro这些虚拟Sensor。
这些Sensor又是如何与Kernel通信的呢,我们在第七节会来分析。
最后这个run方法不得不介绍,其实SensorService是继承了Thread,而线程函数就是threadLoop,这个threadLoop在干什么呢?我们也放到第七节来讲吧!
好SensorService的初始化工作也看完了。
9、返回到SensorManager(Java)
首先它也会获取Sensor列表。
然后创建SensorEventPool和SensorThread,但这儿还没有用到,在第六节会用到。
五、获取Sensor
- public Sensor getDefaultSensor(int type) {
- // TODO: need to be smarter, for now, just return the 1st sensor
- List<Sensor> l = getSensorList(type);
- return l.isEmpty() ? null : l.get(0);
- }
public Sensor getDefaultSensor(int type) { // TODO: need to be smarter, for now, just return the 1st sensor List<Sensor> l = getSensorList(type); return l.isEmpty() ? null : l.get(0); }这个很简单就不用解释了。
六、注册SensorLisenter
1. new ListenerDelegate(SensorEventListener listener, Sensor sensor, Handler handler)
这儿要特别说明一下,在这个构造函数中会创建一个Handler,它会在获取到Sensor数据的时候被调用。
- mHandler = new Handler(looper) {
- @Override
- public void handleMessage(Message msg) {
- final SensorEvent t = (SensorEvent)msg.obj;
- final int handle = t.sensor.getHandle();
- switch (t.sensor.getType()) {
- // Only report accuracy for sensors that support it.
- case Sensor.TYPE_MAGNETIC_FIELD:
- case Sensor.TYPE_ORIENTATION:
- // call onAccuracyChanged() only if the value changes
- final int accuracy = mSensorAccuracies.get(handle);
- if ((t.accuracy >= 0) && (accuracy != t.accuracy)) {
- mSensorAccuracies.put(handle, t.accuracy);
- mSensorEventListener.onAccuracyChanged(t.sensor, t.accuracy);
- }
- break;
- default:
- // For other sensors, just report the accuracy once
- if (mFirstEvent.get(handle) == false) {
- mFirstEvent.put(handle, true);
- mSensorEventListener.onAccuracyChanged(
- t.sensor, SENSOR_STATUS_ACCURACY_HIGH);
- }
- break;
- }
- mSensorEventListener.onSensorChanged(t);
- sPool.returnToPool(t);
- }
- };
mHandler = new Handler(looper) { @Override public void handleMessage(Message msg) { final SensorEvent t = (SensorEvent)msg.obj; final int handle = t.sensor.getHandle(); switch (t.sensor.getType()) { // Only report accuracy for sensors that support it. case Sensor.TYPE_MAGNETIC_FIELD: case Sensor.TYPE_ORIENTATION: // call onAccuracyChanged() only if the value changes final int accuracy = mSensorAccuracies.get(handle); if ((t.accuracy >= 0) && (accuracy != t.accuracy)) { mSensorAccuracies.put(handle, t.accuracy); mSensorEventListener.onAccuracyChanged(t.sensor, t.accuracy); } break; default: // For other sensors, just report the accuracy once if (mFirstEvent.get(handle) == false) { mFirstEvent.put(handle, true); mSensorEventListener.onAccuracyChanged( t.sensor, SENSOR_STATUS_ACCURACY_HIGH); } break; } mSensorEventListener.onSensorChanged(t); sPool.returnToPool(t); } };2. sensors_create_queue
要注意一下SensorEventConnection的构造
- SensorService::SensorEventConnection::SensorEventConnection(
- const sp<SensorService>& service)
- : mService(service), mChannel(new SensorChannel())
- {
- }
SensorService::SensorEventConnection::SensorEventConnection( const sp<SensorService>& service) : mService(service), mChannel(new SensorChannel()){}SensorChannel构造://这部分还没有搞懂,这个管道的具体功能,接着往下分析希望能搞明白
- SensorChannel::SensorChannel()
- : mSendFd(-1), mReceiveFd(-1)
- {
- int fds[2];
- if (pipe(fds) == 0) {
- mReceiveFd = fds[0];
- mSendFd = fds[1];
- fcntl(mReceiveFd, F_SETFL, O_NONBLOCK);
- fcntl(mSendFd, F_SETFL, O_NONBLOCK);
- }
- }
SensorChannel::SensorChannel() : mSendFd(-1), mReceiveFd(-1){ int fds[2]; if (pipe(fds) == 0) { mReceiveFd = fds[0]; mSendFd = fds[1]; fcntl(mReceiveFd, F_SETFL, O_NONBLOCK); fcntl(mSendFd, F_SETFL, O_NONBLOCK); }}3. sensors_data_poll
七、Sensor的数据处理流程
八、校准
初始化校准
它都是把校准数据写在一些文件里的,qcom 7627a的路径是:
/persist/GsensorCalibrationData
/persist/MsensorCalibrationData
/persist/PSensorCalibrateData
然后在Hal中对应的Sensor的构造函数中去读数据,如P-sensor对应的TmdSensor
- ioctl(dev_fd, TAOS_IOCTL_ALS_CALIBRATE, 0);
- if((fp = fopen(PSENSOR_CALIBRATED_DATA_FILE, "r+"))!= NULL)
- {
- fscanf(fp,"%d %d\n",&TaosProxCalibateData[0],&TaosProxCalibateData[1]);
- fclose( fp );
- if((TaosProxCalibateData[0] > 0) && (TaosProxCalibateData[1] < 1023) && (TaosProxCalibateData[0] < TaosProxCalibateData[1]))
- ioctl(dev_fd,TAOS_IOCTL_SET_PROX_CALIBRATE_DATA,&TaosProxCalibateData);
- else
- ioctl(dev_fd, TAOS_IOCTL_PROX_CALIBRATE, 0);
- }
- else
- {
- ioctl(dev_fd, TAOS_IOCTL_PROX_CALIBRATE, 0);
- }
ioctl(dev_fd, TAOS_IOCTL_ALS_CALIBRATE, 0);if((fp = fopen(PSENSOR_CALIBRATED_DATA_FILE, "r+"))!= NULL){fscanf(fp,"%d %d\n",&TaosProxCalibateData[0],&TaosProxCalibateData[1]);fclose( fp );if((TaosProxCalibateData[0] > 0) && (TaosProxCalibateData[1] < 1023) && (TaosProxCalibateData[0] < TaosProxCalibateData[1]))ioctl(dev_fd,TAOS_IOCTL_SET_PROX_CALIBRATE_DATA,&TaosProxCalibateData);else ioctl(dev_fd, TAOS_IOCTL_PROX_CALIBRATE, 0);}else{ioctl(dev_fd, TAOS_IOCTL_PROX_CALIBRATE, 0);}发ioctl到Tmd驱动程序中去,其实这个功能比较的简单,从TaosProxcalibateData的定义可以看出就是传一个大值和一个小值。
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