added local pool doc

doc/README-localpools.md

@@ -1,4 +1,4 @@
-## Local Data Pools
+## Local Data Pools Developer Information
 
 The local data pools can be used to store data like sensor values so they can be used 
 by other software objects like controllers as well. If a class should have a local pool which
@@ -20,10 +20,136 @@ access to the pool data is done via proxy classes like pool variable classes or
 Generally, a user will create a dataset class which in turn groups all cohesive pool variables.
 
 The user can then use this set class to `read` the variables and `commit` changed variables
-back into the pool.
+back into the pool. The general approach is that a user will create a header containing the set
+class. For example, the following code shows an implementation to access data from a Gyroscope:
 
-### Using the local data pools of the `DeviceHandlerBase`
+```cpp
+class GyroPrimaryDataset: public StaticLocalDataSet<3 * sizeof(float)> {
+public:
+    /**
+     * Constructor for data users
+     * @param gyroId
+     */
+    GyroPrimaryDataset(object_id_t gyroId):
+            StaticLocalDataSet(sid_t(gyroId, gyrodefs::GYRO_DATA_SET_ID)) {
+        setAllVariablesReadOnly();
+    }
+
+    lp_var_t<float> angVelocityX = lp_var_t<float>(sid.objectId,
+            gyrodefs::ANGULAR_VELOCITY_X, this);
+    lp_var_t<float> angVelocityY = lp_var_t<float>(sid.objectId,
+            gyrodefs::ANGULAR_VELOCITY_Y, this);
+    lp_var_t<float> angVelocityZ = lp_var_t<float>(sid.objectId,
+            gyrodefs::ANGULAR_VELOCITY_Z, this);
+private:
+
+    friend class GyroHandler;
+    /**
+     * Constructor for data creator
+     * @param hkOwner
+     */
+    GyroPrimaryDataset(HasLocalDataPoolIF* hkOwner):
+            StaticLocalDataSet(hkOwner, gyrodefs::GYRO_DATA_SET_ID) {}
+};
+```
+
+There is a constructor for users which sets all variables to read-only and there is the constructor
+for the GyroHandler data creator. Both the atittude controller and the `GyroHandler` can now
+use the same class definition to access the pool variables with `read` and `commit` semantics
+in a thread-safe way. Generally, each class requiring access will have the set class as a member
+class. The data creator will also be generally a `DeviceHandlerBase` subclass and some additional
+steps are necessary to expose the set for housekeeping purposes.
+
+### Using the local data pools in a `DeviceHandlerBase` subclass
 
 It is very common to store data generated by devices like a sensor into a pool which can 
 then be used by other objects. Therefore, the `DeviceHandlerBase` already has a
-local pool. The
+local pool. Using the aforementioned example, our `GyroHandler` will now have the set class
+as a member:
+
+```cpp
+class GyroHandler: ... {
+
+public:
+	...
+private:
+	...
+	GyroPrimaryDataset gyroData;
+	...
+};
+```
+
+The constructor used for the creators expects the owner class as a parameter, so we initialize
+the object in the `GyroHandler` constructor like this:
+
+```cpp
+GyroHandler::GyroHandler(object_id_t objectId, object_id_t comIF,
+        CookieIF *comCookie, uint8_t switchId):
+        DeviceHandlerBase(objectId, comIF, comCookie), switchId(switchId),
+		gyroData(this) {}
+```
+
+We need to assign the set to a reply ID used in the `DeviceHandlerBase`. 
+The combination of the `GyroHandler` object ID and the reply ID will be the 64-bit structure ID
+`sid_t` and is used to globally identify the set, for example when requesting housekeeping data or
+generating update messages. We need to assign our custom in some way so that the local pool manager
+can access the custom data sets as well.
+By default, the `getDataSetHandle` will take care of this tasks. The default implementation for a
+`DeviceHandlerBase` subclass will use the internal command map to retrieve 
+a handle to a dataset from a given reply ID. Therefore,
+we assign the set in the `fillCommandAndReplyMap` function:
+
+```cpp
+void GyroHandler::fillCommandAndReplyMap() {
+	...
+	this->insertInCommandAndReplyMap(gyrodefs::GYRO_DATA, 3, &gyroData);
+	...
+}
+```
+
+Now, we need to create the actual pool entries as well, using the `initializeLocalDataPool` 
+function. Here, we also immediately subscribe for periodic housekeeping packets 
+with an interval of 4 seconds. They are still disabled in this example and can be enabled 
+with a housekeeping service command.
+
+```cpp
+ReturnValue_t GyroHandler::initializeLocalDataPool(localpool::DataPool &localDataPoolMap,
+		LocalDataPoolManager &poolManager) {
+	localDataPoolMap.emplace(gyrodefs::ANGULAR_VELOCITY_X,
+			new PoolEntry<float>({0.0}));
+	localDataPoolMap.emplace(gyrodefs::ANGULAR_VELOCITY_Y,
+			new PoolEntry<float>({0.0}));
+	localDataPoolMap.emplace(gyrodefs::ANGULAR_VELOCITY_Z,
+			new PoolEntry<float>({0.0}));
+	localDataPoolMap.emplace(gyrodefs::GENERAL_CONFIG_REG42,
+			new PoolEntry<uint8_t>({0}));
+	localDataPoolMap.emplace(gyrodefs::RANGE_CONFIG_REG43,
+			new PoolEntry<uint8_t>({0}));
+
+	poolManager.subscribeForPeriodicPacket(gyroData.getSid(), false, 4.0, false);
+	return HasReturnvaluesIF::RETURN_OK;
+}
+```
+
+Now, we have received some sensor data and converted them into the right format, 
+we can write it into the pool like this, using a guard class to ensure the set is commited back 
+in any case:
+
+```cpp
+PoolReadGuard readHelper(&gyroData);
+if(readHelper.getReadResult() == HasReturnvaluesIF::RETURN_OK) {
+	if(not gyroData.isValid()) {
+		gyroData.setValidity(true, true);
+	}
+
+	gyroData.angVelocityX = angularVelocityX;
+	gyroData.angVelocityY = angularVelocityY;
+	gyroData.angVelocityZ = angularVelocityZ;
+}
+```
+
+### Using the local data pools in a `ExtendedControllerBase` subclass
+
+Coming soon
+
+