Callback_agg_convert_setting()

Description:	Callback procedure, invoked every time a setting A-variable is being read or written. Provides an opportunity to convert the value before writing to a setting or after reading from a setting. Procedure body has to be created elsewhere in the project (externally with respect to the library).
Syntax:	sub callback_agg_convert_setting(byref setting_name as string, index as byte, byref setting_value as string, op as en_agg_rdwr)
Returns:	---
See Also:	Adding Setting A-variables Callback_agg_convert_event_field()

Parameter	Description
setting_name	Name of the setting being read or written.
index	Setting index (zero for single-value settings).
setting_value	Value to be converted. This argument is also used for returning the converted value: take setting_value, modify as needed, and store back.
op	EN_AGG_GET- reading from the setting EN_AGG_SET- writing to the setting

Details

This procedure allows to store the value in a format or type that is different from the way the same is perceived in AggreGate.

Here is a simple example: Supposing, there is a setting that stores device temperature. The setting data originates from a temperature measuring IC, which outputs a byte value. Seven most significant bits are degrees. The least significant bit represent a 0.5-degree step. The output of 0 corresponds to -40 degrees C. Therefore, the output of 255 corresponds to +87.5 degrees C.

Now, the operator in AggreGare would surely prefer to see "natural" temperature values like -40 and +87.5, rather than 0 and 255. This procedure can provide a place to do the conversion.

The same possibility exists for stored event's fields (see Callback_agg_convert_event_field()) but not for table A-variables. Tables must be stored in exactly the same way that the AggreGate server "believes" them to be stored. This is because table synchronization is based on hash strings.