store/src/main/java/tools/refinery/data/model/TupleHashProviderBitMagic.java


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package tools.refinery.data.model;

import tools.refinery.data.map.ContinousHashProvider;

public class TupleHashProviderBitMagic implements ContinousHashProvider<Tuple> {

	@Override
	public int getHash(Tuple key, int index) {
		if(key.getSize() == 1) {
			return key.get(0);
		}
		
		int result = 0;
		final int startBitIndex = index*30;
		final int finalBitIndex = startBitIndex+30;
		final int arity = key.getSize();
		
		for(int i = startBitIndex; i<=finalBitIndex; i++) {
			final int selectedKey = key.get(i%arity);
			final int selectedPosition = 1<<(i/arity);
			if((selectedKey&selectedPosition) != 0) {
				result |= 1<<(i%30);
			}
		}
		
		return result;
	}
}