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improved readme

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Robin Müller 2021-03-04 17:58:07 +01:00
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doc/README-localpools.md
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## Local Data Pools Developer Information ## Local Data Pools Developer Information
The local data pools can be used to store data like sensor values so they can be used 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 by other software objects like controllers as well. If a custom class should have a local pool which
can be used by other software objects as well, following steps have to be performed: can be used by other software objects as well, following steps have to be performed:
1. Create a `LocalDataPoolManager` member class 1. Create a `LocalDataPoolManager` member object in the custom class
2. Implement the `HasLocalDataPoolIF` 2. Implement the `HasLocalDataPoolIF` with specifies the interface between the local pool manager
and the class owning the local pool.
The local data pool manager is also able to process housekeeping service requests in form The local data pool manager is also able to process housekeeping service requests in form
of messages, generate periodic housekeeping packet, generate notification and snapshots of changed of messages, generate periodic housekeeping packet, generate notification and snapshots of changed
variables and datasets and process notifications and snapshots coming from other objects. variables and datasets and process notifications and snapshots coming from other objects.
Two important framework classes already perform the two steps shown above so the steps required The two former tasks are related to the external interface using telemetry and telecommands (TMTC)
are altered slightly. while the later two are related to data consumers like controllers only acting on data change
detected by the data creator instead of checking the data manually each cycle. Two important
framework classes `DeviceHandlerBase` and `ExtendedControllerBase` already perform the two steps
shown above so the steps required are altered slightly.
### Storing and Accessing pool data ### Storing and Accessing pool data
The pool manager is responsible for thread-safe access of the pool data, but the actual The pool manager is responsible for thread-safe access of the pool data, but the actual
access to the pool data is done via proxy classes like pool variable classes or dataset classes. access to the pool data from the point of a mission software developer is given in form of
Generally, a user will create a dataset class which in turn groups all cohesive pool variables. proxy classes like pool variable classes. These classes store a copy
of the pool variable with the matching datatype and copy the actual data from the local pool
on a `read` call. Changed variables can then be written to the local pool with a `commit` call.
The `read` and `commit` calls are thread-safe and can be called concurrently from data creators
and data consumers. Generally, a user will create a dataset class which in turn groups all
cohesive pool variables. These sets simply iterator over the list of variables and call the
`read` and `commit` functions of each variable.
The user can then use this set class to `read` the variables and `commit` changed variables An example is shown for using the local data pools with a Gyroscope.
back into the pool. The general approach is that a user will create a header containing the set For example, the following code shows an implementation to access data from a Gyroscope taken
class. For example, the following code shows an implementation to access data from a Gyroscope: from the SOURCE CubeSat project:
```cpp ```cpp
class GyroPrimaryDataset: public StaticLocalDataSet<3 * sizeof(float)> { class GyroPrimaryDataset: public StaticLocalDataSet<3 * sizeof(float)> {
@ -53,8 +63,9 @@ private:
}; };
``` ```
There is a constructor for users which sets all variables to read-only and there is the constructor There is a public constructor for users which sets all variables to read-only and there is a
for the GyroHandler data creator. Both the atittude controller and the `GyroHandler` can now constructor for the GyroHandler data creator by makring it private and declaring the `GyroHandler`
as a friend class. Both the atittude controller and the `GyroHandler` can now
use the same class definition to access the pool variables with `read` and `commit` semantics 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 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 class. The data creator will also be generally a `DeviceHandlerBase` subclass and some additional
@ -148,6 +159,8 @@ if(readHelper.getReadResult() == HasReturnvaluesIF::RETURN_OK) {
} }
``` ```
The guard class will commit the changed data on destruction automatically.
### Using the local data pools in a `ExtendedControllerBase` subclass ### Using the local data pools in a `ExtendedControllerBase` subclass
Coming soon Coming soon