Add API for writable object property lists (#1206)

Added a new API for writable property lists across all the basic example object types, preparing for the introduction of a Writable_Property_List property in every object in a future BACnet standard revision.

The lists can be used by backup and restore feature to automatically choose the object property values in the backup that can be restored via internal WriteProperty directly from BACnet CreateObject services with  List of Initial Values. 

Updated existing device object examples to include these writable property lists.

apps/piface/configure.sh

@@ -10,7 +10,7 @@ fi
 
 if [ ! -d "libpifacedigital" ]
 then
-    git clone https://github.com:piface/libpifacedigital.git
+    git clone https://github.com/piface/libpifacedigital.git
 fi
 
 # Build the library

apps/piface/device.c

@@ -56,7 +56,8 @@ static object_functions_t My_Object_Table[] = {
       NULL /* Remove_List_Element */,
       NULL /* Create */,
       NULL /* Delete */,
-      NULL /* Timer */ },
+      NULL /* Timer */,
+      Device_Writable_Property_List },
 #if (BACNET_PROTOCOL_REVISION >= 17)
     { OBJECT_NETWORK_PORT,
       Network_Port_Init,
@@ -77,7 +78,8 @@ static object_functions_t My_Object_Table[] = {
       NULL /* Remove_List_Element */,
       NULL /* Create */,
       NULL /* Delete */,
-      NULL /* Timer */ },
+      NULL /* Timer */,
+      Network_Port_Writable_Property_List },
 #endif
     { OBJECT_BINARY_INPUT,
       Binary_Input_Init,
@@ -98,7 +100,8 @@ static object_functions_t My_Object_Table[] = {
       NULL /* Remove_List_Element */,
       NULL /* Create */,
       NULL /* Delete */,
-      NULL /* Timer */ },
+      NULL /* Timer */,
+      Binary_Input_Writable_Property_List },
     { OBJECT_BINARY_LIGHTING_OUTPUT,
       Binary_Lighting_Output_Init,
       Binary_Lighting_Output_Count,
@@ -118,7 +121,8 @@ static object_functions_t My_Object_Table[] = {
       NULL /* Remove_List_Element */,
       Binary_Lighting_Output_Create,
       Binary_Lighting_Output_Delete,
-      Binary_Lighting_Output_Timer },
+      Binary_Lighting_Output_Timer,
+      Binary_Lighting_Output_Writable_Property_List },
     { OBJECT_BINARY_OUTPUT,
       Binary_Output_Init,
       Binary_Output_Count,
@@ -138,7 +142,8 @@ static object_functions_t My_Object_Table[] = {
       NULL /* Remove_List_Element */,
       Binary_Output_Create,
       Binary_Output_Delete,
-      NULL /* Timer */ },
+      NULL /* Timer */,
+      Binary_Output_Writable_Property_List },
     { MAX_BACNET_OBJECT_TYPE,
       NULL /* Init */,
       NULL /* Count */,
@@ -158,7 +163,8 @@ static object_functions_t My_Object_Table[] = {
       NULL /* Remove_List_Element */,
       NULL /* Create */,
       NULL /* Delete */,
-      NULL /* Timer */ }
+      NULL /* Timer */,
+      NULL /* Writable_Property_List */ }
 };
 
 /** Glue function to let the Device object, when called by a handler,
@@ -331,6 +337,34 @@ static const int Device_Properties_Optional[] = {
     -1
 };
 
+/* Every object shall have a Writable Property_List property
+   which is a BACnetARRAY of property identifiers,
+   one property identifier for each property within this object
+   that is always writable.  */
+static const int32_t Writable_Properties[] = {
+    /* unordered list of writable properties */
+    PROP_OBJECT_IDENTIFIER,
+    PROP_NUMBER_OF_APDU_RETRIES,
+    PROP_APDU_TIMEOUT,
+    PROP_VENDOR_IDENTIFIER,
+    PROP_SYSTEM_STATUS,
+    PROP_OBJECT_NAME,
+    PROP_LOCATION,
+    PROP_DESCRIPTION,
+    PROP_MODEL_NAME,
+#if defined(BACNET_TIME_MASTER)
+    PROP_TIME_SYNCHRONIZATION_INTERVAL,
+    PROP_ALIGN_INTERVALS,
+    PROP_INTERVAL_OFFSET,
+#endif
+    PROP_UTC_OFFSET,
+#if defined(BACDL_MSTP)
+    PROP_MAX_INFO_FRAMES,
+    PROP_MAX_MASTER,
+#endif
+    -1
+};
+
 static const int Device_Properties_Proprietary[] = { -1 };
 
 void Device_Property_Lists(
@@ -349,6 +383,20 @@ void Device_Property_Lists(
     return;
 }
 
+/**
+ * @brief Get the list of writable properties for a Device object
+ * @param  object_instance - object-instance number of the object
+ * @param  properties - Pointer to the pointer of writable properties.
+ */
+void Device_Writable_Property_List(
+    uint32_t object_instance, const int32_t **properties)
+{
+    (void)object_instance;
+    if (properties) {
+        *properties = Writable_Properties;
+    }
+}
+
 /* note: you really only need to define variables for
    properties that are writable or that may change.
    The properties that are constant can be hard coded