Aggregator UDF functions

An introduction to functions used in aggregator UDFs, their purposes, and parameters.

C8Bool C8IsPositiveMessage(C8Udf *ctx) – Purpose: Indicates that the message has entered the window (is a positive message). If so, you should add the message to the aggregation.
Parameters:
- ctx: A "context" object that contains information about the parameters passed to the UDF.
Returns: C8_TRUE if the message is positive; otherwise C8_FALSE otherwise.
C8Bool C8IsNegativeMessage(C8Udf *ctx) – Purpose: Indicates that the message has exited the window (is a "negative" message). If so, you should subtract the message to the aggregation.
Parameters:
- ctx: A "context" object that contains information about the parameters passed to the UDF.
Returns:
void C8SetState(C8Udf *ctx, const void *data, C8UInt data_size) – Purpose: Saves the user-defined data structure of data_size bytes. This function copies your data into memory allocated by the server. This memory will persist after your UDF has returned. Retrieve the saved memory by using the C8GetState() function.
Parameters:
- ctx: A "context" object that contains information about the parameters passed to the UDF.
- data: The data that you want to save as state information.
- data_size: The number of bytes of data you are saving.
Returns: Nothing.
const void *C8GetState(C8Udf *ctx, C8UInt *data_size) – Purpose: Obtains the current state. The return value has type void * and should be cast to the user-defined data structure and the data_size pointer will contain the number of bytes in the data structure. The return value is a pointer. You should not change the memory that the pointer points to, and you should not C8Free() this pointer.
Parameters:
- ctx: A "context" object that contains information about the parameters passed to the UDF.
- data_size: A pointer to a location into which the function can insert the number of bytes retrieved.
Returns: A pointer to the memory that was retrieved.