getDownscaledCapacity

Short summary

The method takes the requested size and the current capacity as input and determines the next suitable capacity value based on the implemented resizing strategy. The resulting capacity is returned as newCapacity. It returns true when a downsizing is needed within the used strategy, false if no resizing is needed.

• Return type: BOOL

Parameters

Name	Type	Comment	Kind
requestedSize	UDINT	the new size that is needed	input
currentCapacity	UDINT	the current actual size of the container	input
newCapacity	UDINT	the calculated size of the container	output

Code

Declaration

METHOD getDownscaledCapacity : BOOL
VAR_INPUT
	(* the new size that is needed *)
	requestedSize	: UDINT;
	(* the current actual size of the container *)
	currentCapacity	: UDINT;
END_VAR
VAR_OUTPUT
	(* the calculated size of the container *)
	newCapacity	: UDINT;
END_VAR
VAR CONSTANT
	SHRINKING_THRESHOLD_MULTIPLIER :UDINT := 3;
END_VAR

Implementation

IF (requestedSize < THIS^.initialSize) OR_ELSE (currentCapacity = 0) THEN 
	newCapacity := THIS^.initialSize; 
ELSE 
	newCapacity := currentCapacity;  
	// gradual shrink by cubic root of 0.5 with threshold 
	WHILE ( newCapacity > SHRINKING_THRESHOLD_MULTIPLIER*requestedSize ) DO
		newCapacity := TO_UDINT(TO_REAL(newCapacity) / THIS^.GROW_FACTOR);
	END_WHILE
END_IF;

getDownscaledCapacity := (newCapacity <> currentCapacity);