RegularArrayProperty.java

package de.take_weiland.mods.commons.meta;

import com.google.common.collect.ImmutableMap;

import java.util.Set;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

/**
 * @author diesieben07
 */
final class RegularArrayProperty<T> extends GenericProperty<T> {

	private final ImmutableMap<T, Integer> lookup;
	private final int shift;
	private final int mask;

	RegularArrayProperty(int shift, T[] values) {
		int bitCount = Integer.numberOfTrailingZeros(Integer.highestOneBit(values.length - 1)) + 1;
		checkArgument(shift >= bitCount + 1, "Too many values for given shift (need at least %s)", bitCount - 1);

		this.shift = shift;
		this.mask = (1 << bitCount) - 1;
		ImmutableMap.Builder<T, Integer> b = ImmutableMap.builder();
		for (int i = 0; i < values.length; ++i) {
			b.put(checkNotNull(values[i], "Cannot have null properties!"), i);
		}
		lookup = b.build();
	}

	int toMeta0(T value) {
		Integer i = lookup.get(checkNotNull(value, "value"));
		checkArgument(i != null, "Unknown property %s", value);
		return i;
	}

	@Override
	public final Set<T> values() {
		return lookup.keySet();
	}

	@Override
	public final boolean hasDistinctValues() {
		return true;
	}

	@Override
	public final T value(int metadata) {
		return lookup.keySet().asList().get((metadata >> shift) & mask);
	}

	@Override
	public final int toMeta(T value, int previousMeta) {
		return previousMeta | (toMeta0(value) << shift);
	}
}