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A Minecraft Bedrock Edition server software implementation made in Java from scratch which supports all new features.

There is a newer version: 1.6.0.1-PN

package cn.nukkit.level.util;

import cn.nukkit.math.MathHelper;
import com.google.common.base.Preconditions;

import java.util.Arrays;

public class PaddedBitArray implements BitArray {

    /**
     * Array used to store data
     */
    private final int[] words;

    /**
     * Palette version information
     */
    private final BitArrayVersion version;

    /**
     * Number of entries in this palette (not the length of the words array that internally backs this palette)
     */
    private final int size;

    PaddedBitArray(BitArrayVersion version, int size, int[] words) {
        this.size = size;
        this.version = version;
        this.words = words;
        int expectedWordsLength = MathHelper.ceil((float) size / version.entriesPerWord);
        if (words.length != expectedWordsLength) {
            throw new IllegalArgumentException("Invalid length given for storage, got: " + words.length +
                    " but expected: " + expectedWordsLength);
        }
    }

    @Override
    public void set(int index, int value) {
        Preconditions.checkElementIndex(index, this.size);
        Preconditions.checkArgument(value >= 0 && value <= this.version.maxEntryValue,
                "Max value: %s. Received value", this.version.maxEntryValue, value);
        int arrayIndex = index / this.version.entriesPerWord;
        int offset = (index % this.version.entriesPerWord) * this.version.bits;

        this.words[arrayIndex] = this.words[arrayIndex] & ~(this.version.maxEntryValue << offset) | (value & this.version.maxEntryValue) << offset;
    }

    @Override
    public int get(int index) {
        Preconditions.checkElementIndex(index, this.size);
        int arrayIndex = index / this.version.entriesPerWord;
        int offset = (index % this.version.entriesPerWord) * this.version.bits;

        return (this.words[arrayIndex] >>> offset) & this.version.maxEntryValue;
    }

    @Override
    public int size() {
        return this.size;
    }

    @Override
    public int[] getWords() {
        return this.words;
    }

    @Override
    public BitArrayVersion getVersion() {
        return this.version;
    }

    @Override
    public BitArray copy() {
        return new PaddedBitArray(this.version, this.size, Arrays.copyOf(this.words, this.words.length));
    }
}