[Drivers] Add sensor framework

components/drivers/sensors/SConscript

+# SConscript for sensor framework 
+
+from building import *
+
+cwd = GetCurrentDir()
+src = Glob('*.c') + Glob('*.cpp') 
+CPPPATH = [cwd, cwd + '/../include']
+
+group = DefineGroup('Sensors', src, depend = ['RT_USING_SENSOR', 'RT_USING_DEVICE'], CPPPATH = CPPPATH)
+
+Return('group')
+

components/drivers/sensors/sensor.cpp

+#include <stddef.h>
+#include "sensor.h"
+
+/** 
+ * Sensor
+ */
+Sensor::Sensor()
+{
+	this->next = this->prev = NULL;
+	Subscribe(NULL, NULL);
+}
+
+Sensor::~Sensor()
+{
+}
+
+int Sensor::GetType(void)
+{
+    return this->type;
+}
+
+int Sensor::Subscribe(SensorEventHandler_t *handler, void* user_data)
+{
+    this->evtHandler = handler;
+    this->userData = user_data;
+
+    return 0;
+}
+
+int Sensor::Publish(sensors_event_t* event)
+{
+	if (this->evtHandler != NULL)
+	{
+		/* invoke subscribed handler */
+		(*evtHandler)(this, event, this->userData);
+	}
+
+    return 0;
+}
+
+/**
+ * Sensor Manager
+ */
+/* sensor manager instance */
+static SensorManager _sensor_manager;
+
+SensorManager::SensorManager()
+{
+	sensorList = NULL;
+}
+
+SensorManager::~SensorManager()
+{
+}
+
+int SensorManager::RegisterSensor(Sensor* sensor)
+{
+    SensorManager* self = &_sensor_manager;
+    
+    RT_ASSERT(sensor != RT_NULL);
+
+	/* add sensor into the list */
+	if (self->sensorList = NULL)
+	{
+		sensor->prev = sensor->next = sensor;
+	}
+	else
+	{
+		sensor->prev = self->sensorList;
+		sensor->next = self->sensorList->next;
+
+		self->sensorList->next->prev = sensor;
+		self->sensorList->next = sensor;
+	}
+
+	/* point the sensorList to this sensor */
+	self->sensorList = sensor;
+
+	return 0;
+}
+
+int SensorManager::DeregisterSensor(Sensor* sensor)
+{
+    SensorManager* self = &_sensor_manager;
+
+	/* disconnect sensor list */
+	sensor->next->prev = sensor->prev;
+	sensor->prev->next = sensor->next;
+
+	/* check the sensorList */
+	if (sensor == self->sensorList)
+	{
+		if (sensor->next == sensor) self->sensorList = NULL; /* empty list */
+		else self->sensorList = sensor->next;
+	}
+
+	/* re-initialize sensor node */
+	sensor->next = sensor->prev = sensor;
+
+    return 0;
+}
+
+Sensor *SensorManager::GetDefaultSensor(int type)
+{
+    SensorManager* self = &_sensor_manager;
+	Sensor *sensor = self->sensorList;
+
+	if (sensor == NULL) return NULL;
+
+	do
+	{
+		/* find the same type */
+		if (sensor->GetType() == type) return sensor;
+
+		sensor = sensor->next;
+	}
+	while (sensor != self->sensorList);
+
+    return NULL;
+}
+
+int SensorManager::Subscribe(int type, SensorEventHandler_t *handler, void* user_data)
+{
+	Sensor *sensor;
+
+	sensor = SensorManager::GetDefaultSensor(type);
+	if (sensor != NULL)
+	{
+		sensor->Subscribe(handler, user_data);
+		return 0;
+	}
+
+    return -1;
+}
+