67 lines
2.2 KiB
Java
67 lines
2.2 KiB
Java
/*
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* WorldEdit, a Minecraft world manipulation toolkit
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* Copyright (C) sk89q <http://www.sk89q.com>
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* Copyright (C) WorldEdit team and contributors
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package com.sk89q.worldedit.world.chunk;
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import static com.google.common.base.Preconditions.checkElementIndex;
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public class PackedIntArrayReader {
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private static final int[] FACTORS = new int[64];
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static {
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FACTORS[0] = -1;
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for (int i = 2; i <= 64; i++) {
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FACTORS[i - 1] = (int) (Integer.toUnsignedLong(-1) / i);
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}
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}
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private static final int SIZE = 4096;
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private final long[] data;
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private final int elementBits;
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private final long maxValue;
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private final int elementsPerLong;
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private final int factor;
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public PackedIntArrayReader(long[] data) {
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this.data = data;
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this.elementBits = data.length * 64 / 4096;
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this.maxValue = (1L << elementBits) - 1L;
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this.elementsPerLong = 64 / elementBits;
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this.factor = FACTORS[elementsPerLong - 1];
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int j = (SIZE + this.elementsPerLong - 1) / this.elementsPerLong;
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if (j != data.length) {
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throw new IllegalStateException("Invalid packed-int array provided, should be of length " + j);
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}
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}
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public int get(int index) {
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checkElementIndex(index, SIZE);
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int i = this.adjustIndex(index);
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long l = this.data[i];
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int j = (index - i * this.elementsPerLong) * this.elementBits;
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return (int) (l >> j & this.maxValue);
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}
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private int adjustIndex(int i) {
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return (int) ((long) i * factor + factor >> 32);
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}
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}
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