org.opensearch.geometry.utils.BitUtil Maven / Gradle / Ivy
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* SPDX-License-Identifier: Apache-2.0
*
* The OpenSearch Contributors require contributions made to
* this file be licensed under the Apache-2.0 license or a
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*/
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing,
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/*
* Modifications Copyright OpenSearch Contributors. See
* GitHub history for details.
*/
package org.opensearch.geometry.utils;
/**
* Utilities for common Bit twiddling methods. Borrowed heavily from Lucene (org.apache.lucene.util.BitUtil).
*/
public class BitUtil { // magic numbers for bit interleaving
private static final long MAGIC[] = {
0x5555555555555555L,
0x3333333333333333L,
0x0F0F0F0F0F0F0F0FL,
0x00FF00FF00FF00FFL,
0x0000FFFF0000FFFFL,
0x00000000FFFFFFFFL,
0xAAAAAAAAAAAAAAAAL };
// shift values for bit interleaving
private static final short SHIFT[] = { 1, 2, 4, 8, 16 };
/**
* Interleaves the first 32 bits of each long value
*
* Adapted from: http://graphics.stanford.edu/~seander/bithacks.html#InterleaveBMN
*/
public static long interleave(int even, int odd) {
long v1 = 0x00000000FFFFFFFFL & even;
long v2 = 0x00000000FFFFFFFFL & odd;
v1 = (v1 | (v1 << SHIFT[4])) & MAGIC[4];
v1 = (v1 | (v1 << SHIFT[3])) & MAGIC[3];
v1 = (v1 | (v1 << SHIFT[2])) & MAGIC[2];
v1 = (v1 | (v1 << SHIFT[1])) & MAGIC[1];
v1 = (v1 | (v1 << SHIFT[0])) & MAGIC[0];
v2 = (v2 | (v2 << SHIFT[4])) & MAGIC[4];
v2 = (v2 | (v2 << SHIFT[3])) & MAGIC[3];
v2 = (v2 | (v2 << SHIFT[2])) & MAGIC[2];
v2 = (v2 | (v2 << SHIFT[1])) & MAGIC[1];
v2 = (v2 | (v2 << SHIFT[0])) & MAGIC[0];
return (v2 << 1) | v1;
}
/**
* Extract just the even-bits value as a long from the bit-interleaved value
*/
public static long deinterleave(long b) {
b &= MAGIC[0];
b = (b ^ (b >>> SHIFT[0])) & MAGIC[1];
b = (b ^ (b >>> SHIFT[1])) & MAGIC[2];
b = (b ^ (b >>> SHIFT[2])) & MAGIC[3];
b = (b ^ (b >>> SHIFT[3])) & MAGIC[4];
b = (b ^ (b >>> SHIFT[4])) & MAGIC[5];
return b;
}
/**
* flip flops odd with even bits
*/
public static final long flipFlop(final long b) {
return ((b & MAGIC[6]) >>> 1) | ((b & MAGIC[0]) << 1);
}
}