src/sensor/SDL_sensor.c - external/github.com/libsdl-org/SDL - Git at Google

 /*
   Simple DirectMedia Layer
   Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>

   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
   arising from the use of this software.

   Permission is granted to anyone to use this software for any purpose,
   including commercial applications, and to alter it and redistribute it
   freely, subject to the following restrictions:

   1. The origin of this software must not be misrepresented; you must not
      claim that you wrote the original software. If you use this software
      in a product, an acknowledgment in the product documentation would be
      appreciated but is not required.
   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original software.
   3. This notice may not be removed or altered from any source distribution.
 */
 #include "SDL_internal.h"

 // This is the sensor API for Simple DirectMedia Layer

 #include "SDL_syssensor.h"

 #include "../events/SDL_events_c.h"
 #include "../joystick/SDL_gamepad_c.h"

 static SDL_SensorDriver *SDL_sensor_drivers[] = {
 #ifdef SDL_SENSOR_ANDROID
     &SDL_ANDROID_SensorDriver,
 #endif
 #ifdef SDL_SENSOR_COREMOTION
     &SDL_COREMOTION_SensorDriver,
 #endif
 #ifdef SDL_SENSOR_WINDOWS
     &SDL_WINDOWS_SensorDriver,
 #endif
 #ifdef SDL_SENSOR_VITA
     &SDL_VITA_SensorDriver,
 #endif
 #ifdef SDL_SENSOR_N3DS
     &SDL_N3DS_SensorDriver,
 #endif
 #if defined(SDL_SENSOR_DUMMY) || defined(SDL_SENSOR_DISABLED)
     &SDL_DUMMY_SensorDriver
 #endif
 };

 #ifndef SDL_THREAD_SAFETY_ANALYSIS
 static
 #endif
 SDL_Mutex *SDL_sensor_lock = NULL; // This needs to support recursive locks
 static SDL_AtomicInt SDL_sensor_lock_pending;
 static int SDL_sensors_locked;
 static bool SDL_sensors_initialized;
 static SDL_Sensor *SDL_sensors SDL_GUARDED_BY(SDL_sensor_lock) = NULL;

 #define CHECK_SENSOR_MAGIC(sensor, result)                  \
     if (!SDL_ObjectValid(sensor, SDL_OBJECT_TYPE_SENSOR)) { \
         SDL_InvalidParamError("sensor");                    \
         SDL_UnlockSensors();                                \
         return result;                                      \
     }

 bool SDL_SensorsInitialized(void)
 {
     return SDL_sensors_initialized;
 }

 void SDL_LockSensors(void)
 {
     (void)SDL_AtomicIncRef(&SDL_sensor_lock_pending);
     SDL_LockMutex(SDL_sensor_lock);
     (void)SDL_AtomicDecRef(&SDL_sensor_lock_pending);

     ++SDL_sensors_locked;
 }

 void SDL_UnlockSensors(void)
 {
     bool last_unlock = false;

     --SDL_sensors_locked;

     if (!SDL_sensors_initialized) {
         // NOTE: There's a small window here where another thread could lock the mutex after we've checked for pending locks
         if (!SDL_sensors_locked && SDL_GetAtomicInt(&SDL_sensor_lock_pending) == 0) {
             last_unlock = true;
         }
     }

     /* The last unlock after sensors are uninitialized will cleanup the mutex,
      * allowing applications to lock sensors while reinitializing the system.
      */
     if (last_unlock) {
         SDL_Mutex *sensor_lock = SDL_sensor_lock;

         SDL_LockMutex(sensor_lock);
         {
             SDL_UnlockMutex(SDL_sensor_lock);

             SDL_sensor_lock = NULL;
         }
         SDL_UnlockMutex(sensor_lock);
         SDL_DestroyMutex(sensor_lock);
     } else {
         SDL_UnlockMutex(SDL_sensor_lock);
     }
 }

 bool SDL_SensorsLocked(void)
 {
     return (SDL_sensors_locked > 0);
 }

 void SDL_AssertSensorsLocked(void)
 {
     SDL_assert(SDL_SensorsLocked());
 }

 bool SDL_InitSensors(void)
 {
     int i;
     bool status;

     // Create the sensor list lock
     if (SDL_sensor_lock == NULL) {
         SDL_sensor_lock = SDL_CreateMutex();
     }

     if (!SDL_InitSubSystem(SDL_INIT_EVENTS)) {
         return false;
     }

     SDL_LockSensors();

     SDL_sensors_initialized = true;

     status = false;
     for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
         if (SDL_sensor_drivers[i]->Init()) {
             status = true;
         }
     }

     SDL_UnlockSensors();

     if (!status) {
         SDL_QuitSensors();
     }

     return status;
 }

 bool SDL_SensorsOpened(void)
 {
     bool opened;

     SDL_LockSensors();
     {
         if (SDL_sensors != NULL) {
             opened = true;
         } else {
             opened = false;
         }
     }
     SDL_UnlockSensors();

     return opened;
 }

 SDL_SensorID *SDL_GetSensors(int *count)
 {
     int i, num_sensors, device_index;
     int sensor_index = 0, total_sensors = 0;
     SDL_SensorID *sensors;

     SDL_LockSensors();
     {
         for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
             total_sensors += SDL_sensor_drivers[i]->GetCount();
         }

         sensors = (SDL_SensorID *)SDL_malloc((total_sensors + 1) * sizeof(*sensors));
         if (sensors) {
             if (count) {
                 *count = total_sensors;
             }

             for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
                 num_sensors = SDL_sensor_drivers[i]->GetCount();
                 for (device_index = 0; device_index < num_sensors; ++device_index) {
                     SDL_assert(sensor_index < total_sensors);
                     sensors[sensor_index] = SDL_sensor_drivers[i]->GetDeviceInstanceID(device_index);
                     SDL_assert(sensors[sensor_index] > 0);
                     ++sensor_index;
                 }
             }
             SDL_assert(sensor_index == total_sensors);
             sensors[sensor_index] = 0;
         } else {
             if (count) {
                 *count = 0;
             }
         }
     }
     SDL_UnlockSensors();

     return sensors;
 }

 /*
  * Get the driver and device index for a sensor instance ID
  * This should be called while the sensor lock is held, to prevent another thread from updating the list
  */
 static bool SDL_GetDriverAndSensorIndex(SDL_SensorID instance_id, SDL_SensorDriver **driver, int *driver_index)
 {
     int i, num_sensors, device_index;

     if (instance_id > 0) {
         for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
             num_sensors = SDL_sensor_drivers[i]->GetCount();
             for (device_index = 0; device_index < num_sensors; ++device_index) {
                 SDL_SensorID sensor_id = SDL_sensor_drivers[i]->GetDeviceInstanceID(device_index);
                 if (sensor_id == instance_id) {
                     *driver = SDL_sensor_drivers[i];
                     *driver_index = device_index;
                     return true;
                 }
             }
         }
     }
     SDL_SetError("Sensor %" SDL_PRIu32 " not found", instance_id);
     return false;
 }

 /*
  * Get the implementation dependent name of a sensor
  */
 const char *SDL_GetSensorNameForID(SDL_SensorID instance_id)
 {
     SDL_SensorDriver *driver;
     int device_index;
     const char *name = NULL;

     SDL_LockSensors();
     if (SDL_GetDriverAndSensorIndex(instance_id, &driver, &device_index)) {
         name = SDL_GetPersistentString(driver->GetDeviceName(device_index));
     }
     SDL_UnlockSensors();

     return name;
 }

 SDL_SensorType SDL_GetSensorTypeForID(SDL_SensorID instance_id)
 {
     SDL_SensorDriver *driver;
     int device_index;
     SDL_SensorType type = SDL_SENSOR_INVALID;

     SDL_LockSensors();
     if (SDL_GetDriverAndSensorIndex(instance_id, &driver, &device_index)) {
         type = driver->GetDeviceType(device_index);
     }
     SDL_UnlockSensors();

     return type;
 }

 int SDL_GetSensorNonPortableTypeForID(SDL_SensorID instance_id)
 {
     SDL_SensorDriver *driver;
     int device_index;
     int type = -1;

     SDL_LockSensors();
     if (SDL_GetDriverAndSensorIndex(instance_id, &driver, &device_index)) {
         type = driver->GetDeviceNonPortableType(device_index);
     }
     SDL_UnlockSensors();

     return type;
 }

 /*
  * Open a sensor for use - the index passed as an argument refers to
  * the N'th sensor on the system.  This index is the value which will
  * identify this sensor in future sensor events.
  *
  * This function returns a sensor identifier, or NULL if an error occurred.
  */
 SDL_Sensor *SDL_OpenSensor(SDL_SensorID instance_id)
 {
     SDL_SensorDriver *driver;
     int device_index;
     SDL_Sensor *sensor;
     SDL_Sensor *sensorlist;
     const char *sensorname = NULL;

     SDL_LockSensors();

     if (!SDL_GetDriverAndSensorIndex(instance_id, &driver, &device_index)) {
         SDL_UnlockSensors();
         return NULL;
     }

     sensorlist = SDL_sensors;
     /* If the sensor is already open, return it
      * it is important that we have a single sensor * for each instance id
      */
     while (sensorlist) {
         if (instance_id == sensorlist->instance_id) {
             sensor = sensorlist;
             ++sensor->ref_count;
             SDL_UnlockSensors();
             return sensor;
         }
         sensorlist = sensorlist->next;
     }

     // Create and initialize the sensor
     sensor = (SDL_Sensor *)SDL_calloc(1, sizeof(*sensor));
     if (!sensor) {
         SDL_UnlockSensors();
         return NULL;
     }
     SDL_SetObjectValid(sensor, SDL_OBJECT_TYPE_SENSOR, true);
     sensor->driver = driver;
     sensor->instance_id = instance_id;
     sensor->type = driver->GetDeviceType(device_index);
     sensor->non_portable_type = driver->GetDeviceNonPortableType(device_index);

     if (!driver->Open(sensor, device_index)) {
         SDL_SetObjectValid(sensor, SDL_OBJECT_TYPE_SENSOR, false);
         SDL_free(sensor);
         SDL_UnlockSensors();
         return NULL;
     }

     sensorname = driver->GetDeviceName(device_index);
     if (sensorname) {
         sensor->name = SDL_strdup(sensorname);
     } else {
         sensor->name = NULL;
     }

     // Add sensor to list
     ++sensor->ref_count;
     // Link the sensor in the list
     sensor->next = SDL_sensors;
     SDL_sensors = sensor;

     driver->Update(sensor);

     SDL_UnlockSensors();

     return sensor;
 }

 /*
  * Find the SDL_Sensor that owns this instance id
  */
 SDL_Sensor *SDL_GetSensorFromID(SDL_SensorID instance_id)
 {
     SDL_Sensor *sensor;

     SDL_LockSensors();
     for (sensor = SDL_sensors; sensor; sensor = sensor->next) {
         if (sensor->instance_id == instance_id) {
             break;
         }
     }
     SDL_UnlockSensors();
     return sensor;
 }

 /*
  * Get the properties associated with a sensor.
  */
 SDL_PropertiesID SDL_GetSensorProperties(SDL_Sensor *sensor)
 {
     SDL_PropertiesID result;

     SDL_LockSensors();
     {
         CHECK_SENSOR_MAGIC(sensor, 0);

         if (sensor->props == 0) {
             sensor->props = SDL_CreateProperties();
         }
         result = sensor->props;
     }
     SDL_UnlockSensors();

     return result;
 }

 /*
  * Get the friendly name of this sensor
  */
 const char *SDL_GetSensorName(SDL_Sensor *sensor)
 {
     const char *result;

     SDL_LockSensors();
     {
         CHECK_SENSOR_MAGIC(sensor, NULL);

         result = SDL_GetPersistentString(sensor->name);
     }
     SDL_UnlockSensors();

     return result;
 }

 /*
  * Get the type of this sensor
  */
 SDL_SensorType SDL_GetSensorType(SDL_Sensor *sensor)
 {
     SDL_SensorType result;

     SDL_LockSensors();
     {
         CHECK_SENSOR_MAGIC(sensor, SDL_SENSOR_INVALID);

         result = sensor->type;
     }
     SDL_UnlockSensors();

     return result;
 }

 /*
  * Get the platform dependent type of this sensor
  */
 int SDL_GetSensorNonPortableType(SDL_Sensor *sensor)
 {
     int result;

     SDL_LockSensors();
     {
         CHECK_SENSOR_MAGIC(sensor, -1);

         result = sensor->non_portable_type;
     }
     SDL_UnlockSensors();

     return result;
 }

 /*
  * Get the instance id for this opened sensor
  */
 SDL_SensorID SDL_GetSensorID(SDL_Sensor *sensor)
 {
     SDL_SensorID result;

     SDL_LockSensors();
     {
         CHECK_SENSOR_MAGIC(sensor, 0);

         result = sensor->instance_id;
     }
     SDL_UnlockSensors();

     return result;
 }

 /*
  * Get the current state of this sensor
  */
 bool SDL_GetSensorData(SDL_Sensor *sensor, float *data, int num_values)
 {
     SDL_LockSensors();
     {
         CHECK_SENSOR_MAGIC(sensor, false);

         num_values = SDL_min(num_values, SDL_arraysize(sensor->data));
         SDL_memcpy(data, sensor->data, num_values * sizeof(*data));
     }
     SDL_UnlockSensors();

     return true;
 }

 /*
  * Close a sensor previously opened with SDL_OpenSensor()
  */
 void SDL_CloseSensor(SDL_Sensor *sensor)
 {
     SDL_Sensor *sensorlist;
     SDL_Sensor *sensorlistprev;

     SDL_LockSensors();
     {
         CHECK_SENSOR_MAGIC(sensor,);

         // First decrement ref count
         if (--sensor->ref_count > 0) {
             SDL_UnlockSensors();
             return;
         }

         SDL_DestroyProperties(sensor->props);

         sensor->driver->Close(sensor);
         sensor->hwdata = NULL;
         SDL_SetObjectValid(sensor, SDL_OBJECT_TYPE_SENSOR, false);

         sensorlist = SDL_sensors;
         sensorlistprev = NULL;
         while (sensorlist) {
             if (sensor == sensorlist) {
                 if (sensorlistprev) {
                     // unlink this entry
                     sensorlistprev->next = sensorlist->next;
                 } else {
                     SDL_sensors = sensor->next;
                 }
                 break;
             }
             sensorlistprev = sensorlist;
             sensorlist = sensorlist->next;
         }

         // Free the data associated with this sensor
         SDL_free(sensor->name);
         SDL_free(sensor);
     }
     SDL_UnlockSensors();
 }

 void SDL_QuitSensors(void)
 {
     int i;

     SDL_LockSensors();

     // Stop the event polling
     while (SDL_sensors) {
         SDL_sensors->ref_count = 1;
         SDL_CloseSensor(SDL_sensors);
     }

     // Quit the sensor setup
     for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
         SDL_sensor_drivers[i]->Quit();
     }

     SDL_QuitSubSystem(SDL_INIT_EVENTS);

     SDL_sensors_initialized = false;

     SDL_UnlockSensors();
 }

 // These are global for SDL_syssensor.c and SDL_events.c

 void SDL_SendSensorUpdate(Uint64 timestamp, SDL_Sensor *sensor, Uint64 sensor_timestamp, float *data, int num_values)
 {
     SDL_AssertSensorsLocked();

     // Allow duplicate events, for things like steps and heartbeats

     // Update internal sensor state
     num_values = SDL_min(num_values, SDL_arraysize(sensor->data));
     SDL_memcpy(sensor->data, data, num_values * sizeof(*data));

     // Post the event, if desired
     if (SDL_EventEnabled(SDL_EVENT_SENSOR_UPDATE)) {
         SDL_Event event;
         event.type = SDL_EVENT_SENSOR_UPDATE;
         event.common.timestamp = timestamp;
         event.sensor.which = sensor->instance_id;
         num_values = SDL_min(num_values, SDL_arraysize(event.sensor.data));
         SDL_memset(event.sensor.data, 0, sizeof(event.sensor.data));
         SDL_memcpy(event.sensor.data, data, num_values * sizeof(*data));
         event.sensor.sensor_timestamp = sensor_timestamp;
         SDL_PushEvent(&event);
     }

     SDL_GamepadSensorWatcher(timestamp, sensor->instance_id, sensor_timestamp, data, num_values);
 }

 void SDL_UpdateSensor(SDL_Sensor *sensor)
 {
     SDL_LockSensors();
     {
         CHECK_SENSOR_MAGIC(sensor,);

         sensor->driver->Update(sensor);
     }
     SDL_UnlockSensors();
 }

 void SDL_UpdateSensors(void)
 {
     int i;
     SDL_Sensor *sensor;

     if (!SDL_WasInit(SDL_INIT_SENSOR)) {
         return;
     }

     SDL_LockSensors();

     for (sensor = SDL_sensors; sensor; sensor = sensor->next) {
         sensor->driver->Update(sensor);
     }

     /* this needs to happen AFTER walking the sensor list above, so that any
        dangling hardware data from removed devices can be free'd
      */
     for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
         SDL_sensor_drivers[i]->Detect();
     }

     SDL_UnlockSensors();
 }
	/*
	Simple DirectMedia Layer
	Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>

	This software is provided 'as-is', without any express or implied
	warranty. In no event will the authors be held liable for any damages
	arising from the use of this software.

	Permission is granted to anyone to use this software for any purpose,
	including commercial applications, and to alter it and redistribute it
	freely, subject to the following restrictions:

	1. The origin of this software must not be misrepresented; you must not
	claim that you wrote the original software. If you use this software
	in a product, an acknowledgment in the product documentation would be
	appreciated but is not required.
	2. Altered source versions must be plainly marked as such, and must not be
	misrepresented as being the original software.
	3. This notice may not be removed or altered from any source distribution.
	*/
	#include "SDL_internal.h"

	// This is the sensor API for Simple DirectMedia Layer

	#include "SDL_syssensor.h"

	#include "../events/SDL_events_c.h"
	#include "../joystick/SDL_gamepad_c.h"

	static SDL_SensorDriver *SDL_sensor_drivers[] = {
	#ifdef SDL_SENSOR_ANDROID
	&SDL_ANDROID_SensorDriver,
	#endif
	#ifdef SDL_SENSOR_COREMOTION
	&SDL_COREMOTION_SensorDriver,
	#endif
	#ifdef SDL_SENSOR_WINDOWS
	&SDL_WINDOWS_SensorDriver,
	#endif
	#ifdef SDL_SENSOR_VITA
	&SDL_VITA_SensorDriver,
	#endif
	#ifdef SDL_SENSOR_N3DS
	&SDL_N3DS_SensorDriver,
	#endif
	#if defined(SDL_SENSOR_DUMMY) \|\| defined(SDL_SENSOR_DISABLED)
	&SDL_DUMMY_SensorDriver
	#endif
	};

	#ifndef SDL_THREAD_SAFETY_ANALYSIS
	static
	#endif
	SDL_Mutex *SDL_sensor_lock = NULL; // This needs to support recursive locks
	static SDL_AtomicInt SDL_sensor_lock_pending;
	static int SDL_sensors_locked;
	static bool SDL_sensors_initialized;
	static SDL_Sensor *SDL_sensors SDL_GUARDED_BY(SDL_sensor_lock) = NULL;

	#define CHECK_SENSOR_MAGIC(sensor, result) \
	if (!SDL_ObjectValid(sensor, SDL_OBJECT_TYPE_SENSOR)) { \
	SDL_InvalidParamError("sensor"); \
	SDL_UnlockSensors(); \
	return result; \
	}

	bool SDL_SensorsInitialized(void)
	{
	return SDL_sensors_initialized;
	}

	void SDL_LockSensors(void)
	{
	(void)SDL_AtomicIncRef(&SDL_sensor_lock_pending);
	SDL_LockMutex(SDL_sensor_lock);
	(void)SDL_AtomicDecRef(&SDL_sensor_lock_pending);

	++SDL_sensors_locked;
	}

	void SDL_UnlockSensors(void)
	{
	bool last_unlock = false;

	--SDL_sensors_locked;

	if (!SDL_sensors_initialized) {
	// NOTE: There's a small window here where another thread could lock the mutex after we've checked for pending locks
	if (!SDL_sensors_locked && SDL_GetAtomicInt(&SDL_sensor_lock_pending) == 0) {
	last_unlock = true;
	}
	}

	/* The last unlock after sensors are uninitialized will cleanup the mutex,
	* allowing applications to lock sensors while reinitializing the system.
	*/
	if (last_unlock) {
	SDL_Mutex *sensor_lock = SDL_sensor_lock;

	SDL_LockMutex(sensor_lock);
	{
	SDL_UnlockMutex(SDL_sensor_lock);

	SDL_sensor_lock = NULL;
	}
	SDL_UnlockMutex(sensor_lock);
	SDL_DestroyMutex(sensor_lock);
	} else {
	SDL_UnlockMutex(SDL_sensor_lock);
	}
	}

	bool SDL_SensorsLocked(void)
	{
	return (SDL_sensors_locked > 0);
	}

	void SDL_AssertSensorsLocked(void)
	{
	SDL_assert(SDL_SensorsLocked());
	}

	bool SDL_InitSensors(void)
	{
	int i;
	bool status;

	// Create the sensor list lock
	if (SDL_sensor_lock == NULL) {
	SDL_sensor_lock = SDL_CreateMutex();
	}

	if (!SDL_InitSubSystem(SDL_INIT_EVENTS)) {
	return false;
	}

	SDL_LockSensors();

	SDL_sensors_initialized = true;

	status = false;
	for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
	if (SDL_sensor_drivers[i]->Init()) {
	status = true;
	}
	}

	SDL_UnlockSensors();

	if (!status) {
	SDL_QuitSensors();
	}

	return status;
	}

	bool SDL_SensorsOpened(void)
	{
	bool opened;

	SDL_LockSensors();
	{
	if (SDL_sensors != NULL) {
	opened = true;
	} else {
	opened = false;
	}
	}
	SDL_UnlockSensors();

	return opened;
	}

	SDL_SensorID SDL_GetSensors(int count)
	{
	int i, num_sensors, device_index;
	int sensor_index = 0, total_sensors = 0;
	SDL_SensorID *sensors;

	SDL_LockSensors();
	{
	for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
	total_sensors += SDL_sensor_drivers[i]->GetCount();
	}

	sensors = (SDL_SensorID )SDL_malloc((total_sensors + 1) sizeof(*sensors));
	if (sensors) {
	if (count) {
	*count = total_sensors;
	}

	for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
	num_sensors = SDL_sensor_drivers[i]->GetCount();
	for (device_index = 0; device_index < num_sensors; ++device_index) {
	SDL_assert(sensor_index < total_sensors);
	sensors[sensor_index] = SDL_sensor_drivers[i]->GetDeviceInstanceID(device_index);
	SDL_assert(sensors[sensor_index] > 0);
	++sensor_index;
	}
	}
	SDL_assert(sensor_index == total_sensors);
	sensors[sensor_index] = 0;
	} else {
	if (count) {
	*count = 0;
	}
	}
	}
	SDL_UnlockSensors();

	return sensors;
	}

	/*
	* Get the driver and device index for a sensor instance ID
	* This should be called while the sensor lock is held, to prevent another thread from updating the list
	*/
	static bool SDL_GetDriverAndSensorIndex(SDL_SensorID instance_id, SDL_SensorDriver *driver, int driver_index)
	{
	int i, num_sensors, device_index;

	if (instance_id > 0) {
	for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
	num_sensors = SDL_sensor_drivers[i]->GetCount();
	for (device_index = 0; device_index < num_sensors; ++device_index) {
	SDL_SensorID sensor_id = SDL_sensor_drivers[i]->GetDeviceInstanceID(device_index);
	if (sensor_id == instance_id) {
	*driver = SDL_sensor_drivers[i];
	*driver_index = device_index;
	return true;
	}
	}
	}
	}
	SDL_SetError("Sensor %" SDL_PRIu32 " not found", instance_id);
	return false;
	}

	/*
	* Get the implementation dependent name of a sensor
	*/
	const char *SDL_GetSensorNameForID(SDL_SensorID instance_id)
	{
	SDL_SensorDriver *driver;
	int device_index;
	const char *name = NULL;

	SDL_LockSensors();
	if (SDL_GetDriverAndSensorIndex(instance_id, &driver, &device_index)) {
	name = SDL_GetPersistentString(driver->GetDeviceName(device_index));
	}
	SDL_UnlockSensors();

	return name;
	}

	SDL_SensorType SDL_GetSensorTypeForID(SDL_SensorID instance_id)
	{
	SDL_SensorDriver *driver;
	int device_index;
	SDL_SensorType type = SDL_SENSOR_INVALID;

	SDL_LockSensors();
	if (SDL_GetDriverAndSensorIndex(instance_id, &driver, &device_index)) {
	type = driver->GetDeviceType(device_index);
	}
	SDL_UnlockSensors();

	return type;
	}

	int SDL_GetSensorNonPortableTypeForID(SDL_SensorID instance_id)
	{
	SDL_SensorDriver *driver;
	int device_index;
	int type = -1;

	SDL_LockSensors();
	if (SDL_GetDriverAndSensorIndex(instance_id, &driver, &device_index)) {
	type = driver->GetDeviceNonPortableType(device_index);
	}
	SDL_UnlockSensors();

	return type;
	}

	/*
	* Open a sensor for use - the index passed as an argument refers to
	* the N'th sensor on the system. This index is the value which will
	* identify this sensor in future sensor events.
	*
	* This function returns a sensor identifier, or NULL if an error occurred.
	*/
	SDL_Sensor *SDL_OpenSensor(SDL_SensorID instance_id)
	{
	SDL_SensorDriver *driver;
	int device_index;
	SDL_Sensor *sensor;
	SDL_Sensor *sensorlist;
	const char *sensorname = NULL;

	SDL_LockSensors();

	if (!SDL_GetDriverAndSensorIndex(instance_id, &driver, &device_index)) {
	SDL_UnlockSensors();
	return NULL;
	}

	sensorlist = SDL_sensors;
	/* If the sensor is already open, return it
	* it is important that we have a single sensor * for each instance id
	*/
	while (sensorlist) {
	if (instance_id == sensorlist->instance_id) {
	sensor = sensorlist;
	++sensor->ref_count;
	SDL_UnlockSensors();
	return sensor;
	}
	sensorlist = sensorlist->next;
	}

	// Create and initialize the sensor
	sensor = (SDL_Sensor )SDL_calloc(1, sizeof(sensor));
	if (!sensor) {
	SDL_UnlockSensors();
	return NULL;
	}
	SDL_SetObjectValid(sensor, SDL_OBJECT_TYPE_SENSOR, true);
	sensor->driver = driver;
	sensor->instance_id = instance_id;
	sensor->type = driver->GetDeviceType(device_index);
	sensor->non_portable_type = driver->GetDeviceNonPortableType(device_index);

	if (!driver->Open(sensor, device_index)) {
	SDL_SetObjectValid(sensor, SDL_OBJECT_TYPE_SENSOR, false);
	SDL_free(sensor);
	SDL_UnlockSensors();
	return NULL;
	}

	sensorname = driver->GetDeviceName(device_index);
	if (sensorname) {
	sensor->name = SDL_strdup(sensorname);
	} else {
	sensor->name = NULL;
	}

	// Add sensor to list
	++sensor->ref_count;
	// Link the sensor in the list
	sensor->next = SDL_sensors;
	SDL_sensors = sensor;

	driver->Update(sensor);

	SDL_UnlockSensors();

	return sensor;
	}

	/*
	* Find the SDL_Sensor that owns this instance id
	*/
	SDL_Sensor *SDL_GetSensorFromID(SDL_SensorID instance_id)
	{
	SDL_Sensor *sensor;

	SDL_LockSensors();
	for (sensor = SDL_sensors; sensor; sensor = sensor->next) {
	if (sensor->instance_id == instance_id) {
	break;
	}
	}
	SDL_UnlockSensors();
	return sensor;
	}

	/*
	* Get the properties associated with a sensor.
	*/
	SDL_PropertiesID SDL_GetSensorProperties(SDL_Sensor *sensor)
	{
	SDL_PropertiesID result;

	SDL_LockSensors();
	{
	CHECK_SENSOR_MAGIC(sensor, 0);

	if (sensor->props == 0) {
	sensor->props = SDL_CreateProperties();
	}
	result = sensor->props;
	}
	SDL_UnlockSensors();

	return result;
	}

	/*
	* Get the friendly name of this sensor
	*/
	const char SDL_GetSensorName(SDL_Sensor sensor)
	{
	const char *result;

	SDL_LockSensors();
	{
	CHECK_SENSOR_MAGIC(sensor, NULL);

	result = SDL_GetPersistentString(sensor->name);
	}
	SDL_UnlockSensors();

	return result;
	}

	/*
	* Get the type of this sensor
	*/
	SDL_SensorType SDL_GetSensorType(SDL_Sensor *sensor)
	{
	SDL_SensorType result;

	SDL_LockSensors();
	{
	CHECK_SENSOR_MAGIC(sensor, SDL_SENSOR_INVALID);

	result = sensor->type;
	}
	SDL_UnlockSensors();

	return result;
	}

	/*
	* Get the platform dependent type of this sensor
	*/
	int SDL_GetSensorNonPortableType(SDL_Sensor *sensor)
	{
	int result;

	SDL_LockSensors();
	{
	CHECK_SENSOR_MAGIC(sensor, -1);

	result = sensor->non_portable_type;
	}
	SDL_UnlockSensors();

	return result;
	}

	/*
	* Get the instance id for this opened sensor
	*/
	SDL_SensorID SDL_GetSensorID(SDL_Sensor *sensor)
	{
	SDL_SensorID result;

	SDL_LockSensors();
	{
	CHECK_SENSOR_MAGIC(sensor, 0);

	result = sensor->instance_id;
	}
	SDL_UnlockSensors();

	return result;
	}

	/*
	* Get the current state of this sensor
	*/
	bool SDL_GetSensorData(SDL_Sensor sensor, float data, int num_values)
	{
	SDL_LockSensors();
	{
	CHECK_SENSOR_MAGIC(sensor, false);

	num_values = SDL_min(num_values, SDL_arraysize(sensor->data));
	SDL_memcpy(data, sensor->data, num_values * sizeof(*data));
	}
	SDL_UnlockSensors();

	return true;
	}

	/*
	* Close a sensor previously opened with SDL_OpenSensor()
	*/
	void SDL_CloseSensor(SDL_Sensor *sensor)
	{
	SDL_Sensor *sensorlist;
	SDL_Sensor *sensorlistprev;

	SDL_LockSensors();
	{
	CHECK_SENSOR_MAGIC(sensor,);

	// First decrement ref count
	if (--sensor->ref_count > 0) {
	SDL_UnlockSensors();
	return;
	}

	SDL_DestroyProperties(sensor->props);

	sensor->driver->Close(sensor);
	sensor->hwdata = NULL;
	SDL_SetObjectValid(sensor, SDL_OBJECT_TYPE_SENSOR, false);

	sensorlist = SDL_sensors;
	sensorlistprev = NULL;
	while (sensorlist) {
	if (sensor == sensorlist) {
	if (sensorlistprev) {
	// unlink this entry
	sensorlistprev->next = sensorlist->next;
	} else {
	SDL_sensors = sensor->next;
	}
	break;
	}
	sensorlistprev = sensorlist;
	sensorlist = sensorlist->next;
	}

	// Free the data associated with this sensor
	SDL_free(sensor->name);
	SDL_free(sensor);
	}
	SDL_UnlockSensors();
	}

	void SDL_QuitSensors(void)
	{
	int i;

	SDL_LockSensors();

	// Stop the event polling
	while (SDL_sensors) {
	SDL_sensors->ref_count = 1;
	SDL_CloseSensor(SDL_sensors);
	}

	// Quit the sensor setup
	for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
	SDL_sensor_drivers[i]->Quit();
	}

	SDL_QuitSubSystem(SDL_INIT_EVENTS);

	SDL_sensors_initialized = false;

	SDL_UnlockSensors();
	}

	// These are global for SDL_syssensor.c and SDL_events.c

	void SDL_SendSensorUpdate(Uint64 timestamp, SDL_Sensor sensor, Uint64 sensor_timestamp, float data, int num_values)
	{
	SDL_AssertSensorsLocked();

	// Allow duplicate events, for things like steps and heartbeats

	// Update internal sensor state
	num_values = SDL_min(num_values, SDL_arraysize(sensor->data));
	SDL_memcpy(sensor->data, data, num_values * sizeof(*data));

	// Post the event, if desired
	if (SDL_EventEnabled(SDL_EVENT_SENSOR_UPDATE)) {
	SDL_Event event;
	event.type = SDL_EVENT_SENSOR_UPDATE;
	event.common.timestamp = timestamp;
	event.sensor.which = sensor->instance_id;
	num_values = SDL_min(num_values, SDL_arraysize(event.sensor.data));
	SDL_memset(event.sensor.data, 0, sizeof(event.sensor.data));
	SDL_memcpy(event.sensor.data, data, num_values * sizeof(*data));
	event.sensor.sensor_timestamp = sensor_timestamp;
	SDL_PushEvent(&event);
	}

	SDL_GamepadSensorWatcher(timestamp, sensor->instance_id, sensor_timestamp, data, num_values);
	}

	void SDL_UpdateSensor(SDL_Sensor *sensor)
	{
	SDL_LockSensors();
	{
	CHECK_SENSOR_MAGIC(sensor,);

	sensor->driver->Update(sensor);
	}
	SDL_UnlockSensors();
	}

	void SDL_UpdateSensors(void)
	{
	int i;
	SDL_Sensor *sensor;

	if (!SDL_WasInit(SDL_INIT_SENSOR)) {
	return;
	}

	SDL_LockSensors();

	for (sensor = SDL_sensors; sensor; sensor = sensor->next) {
	sensor->driver->Update(sensor);
	}

	/* this needs to happen AFTER walking the sensor list above, so that any
	dangling hardware data from removed devices can be free'd
	*/
	for (i = 0; i < SDL_arraysize(SDL_sensor_drivers); ++i) {
	SDL_sensor_drivers[i]->Detect();
	}

	SDL_UnlockSensors();
	}