# Plugins

Plugins are C/C++ shared libraries loaded by the binding to execute some
simple routine. Routine could be on reception of a new signal or at sources
initialization time or signal subscription with the respective JSON field
`onReceived` `init` and `getSignals`

A default plugin (builtin) is provided with 2 functions:

- **defaultOnReceived**: set and record a new signal value and its timestamp
 in the signal composer service. It simply tooks the incoming event JSON object
 and search for *key* `value` and `timestamp` then call function
 `setSignalValue`.
- **setSignalValueWrap**: a `lua2c` function the could be called from any LUA
 script to record a new signal value.

> **CAUTION**: `timestamp` value has to be typed as *uint64_t* with
> a **nanosecond** precision using a realtime clock. To correctly store it in
> a JSON-C object use the int64 type with the according fonctions:
> *json_object_new_int64()*
> *json_object_get_int64()*
> *json_object_set_int64()*
> *...*