org.apache.lucene.util.BitUtil Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.lucene.util; // from org.apache.solr.util rev 555343
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.nio.ByteOrder;
/**
* A variety of high efficiency bit twiddling routines and encoders for primitives.
*
* @lucene.internal
*/
public final class BitUtil {
private BitUtil() {} // no instance
/**
* Native byte order.
*
* Warning: This constant is {@link ByteOrder#nativeOrder()} only in production environments,
* during testing we randomize it. If you need to communicate with native APIs (e.g., Java's
* Panama API), use {@link ByteOrder#nativeOrder()}.
*/
public static final ByteOrder NATIVE_BYTE_ORDER = getNativeByteOrder();
private static ByteOrder getNativeByteOrder() {
try {
var prop = System.getProperty("tests.seed");
if (prop != null) {
return (prop.hashCode() % 2 == 0) ? ByteOrder.LITTLE_ENDIAN : ByteOrder.BIG_ENDIAN;
}
} catch (
@SuppressWarnings("unused")
SecurityException se) {
// fall-through
}
return ByteOrder.nativeOrder();
}
/**
* A {@link VarHandle} to read/write little endian {@code short} from/to a byte array. Shape:
* {@code short vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, short
* val)}
*/
public static final VarHandle VH_LE_SHORT =
MethodHandles.byteArrayViewVarHandle(short[].class, ByteOrder.LITTLE_ENDIAN);
/**
* A {@link VarHandle} to read/write little endian {@code int} from a byte array. Shape: {@code
* int vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, int val)}
*/
public static final VarHandle VH_LE_INT =
MethodHandles.byteArrayViewVarHandle(int[].class, ByteOrder.LITTLE_ENDIAN);
/**
* A {@link VarHandle} to read/write little endian {@code long} from a byte array. Shape: {@code
* long vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, long val)}
*/
public static final VarHandle VH_LE_LONG =
MethodHandles.byteArrayViewVarHandle(long[].class, ByteOrder.LITTLE_ENDIAN);
/**
* A {@link VarHandle} to read/write little endian {@code float} from a byte array. Shape: {@code
* float vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, float val)}
*/
public static final VarHandle VH_LE_FLOAT =
MethodHandles.byteArrayViewVarHandle(float[].class, ByteOrder.LITTLE_ENDIAN);
/**
* A {@link VarHandle} to read/write little endian {@code double} from a byte array. Shape: {@code
* double vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, double val)}
*/
public static final VarHandle VH_LE_DOUBLE =
MethodHandles.byteArrayViewVarHandle(double[].class, ByteOrder.LITTLE_ENDIAN);
/**
* A {@link VarHandle} to read/write native endian {@code short} from/to a byte array. Shape:
* {@code short vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, short
* val)}
*
*
Warning: This handle uses default order only in production environments, during testing we
* randomize it. If you need to communicate with native APIs (e.g., Java's Panama API), use {@link
* ByteOrder#nativeOrder()}.
*/
public static final VarHandle VH_NATIVE_SHORT =
MethodHandles.byteArrayViewVarHandle(short[].class, NATIVE_BYTE_ORDER);
/**
* A {@link VarHandle} to read/write native endian {@code int} from a byte array. Shape: {@code
* int vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, int val)}
*
*
Warning: This handle uses default order only in production environments, during testing we
* randomize it. If you need to communicate with native APIs (e.g., Java's Panama API), use {@link
* ByteOrder#nativeOrder()}.
*/
public static final VarHandle VH_NATIVE_INT =
MethodHandles.byteArrayViewVarHandle(int[].class, NATIVE_BYTE_ORDER);
/**
* A {@link VarHandle} to read/write native endian {@code long} from a byte array. Shape: {@code
* long vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, long val)}
*
*
Warning: This handle uses default order only in production environments, during testing we
* randomize it. If you need to communicate with native APIs (e.g., Java's Panama API), use {@link
* ByteOrder#nativeOrder()}.
*/
public static final VarHandle VH_NATIVE_LONG =
MethodHandles.byteArrayViewVarHandle(long[].class, NATIVE_BYTE_ORDER);
/**
* A {@link VarHandle} to read/write native endian {@code float} from a byte array. Shape: {@code
* float vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, float val)}
*
*
Warning: This handle uses default order only in production environments, during testing we
* randomize it. If you need to communicate with native APIs (e.g., Java's Panama API), use {@link
* ByteOrder#nativeOrder()}.
*/
public static final VarHandle VH_NATIVE_FLOAT =
MethodHandles.byteArrayViewVarHandle(float[].class, NATIVE_BYTE_ORDER);
/**
* A {@link VarHandle} to read/write native endian {@code double} from a byte array. Shape: {@code
* double vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, double val)}
*
*
Warning: This handle uses default order only in production environments, during testing we
* randomize it. If you need to communicate with native APIs (e.g., Java's Panama API), use {@link
* ByteOrder#nativeOrder()}.
*/
public static final VarHandle VH_NATIVE_DOUBLE =
MethodHandles.byteArrayViewVarHandle(double[].class, NATIVE_BYTE_ORDER);
/**
* A {@link VarHandle} to read/write big endian {@code short} from a byte array. Shape: {@code
* short vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, short val)}
*
* @deprecated Better use little endian unless it is needed for backwards compatibility.
*/
@Deprecated
public static final VarHandle VH_BE_SHORT =
MethodHandles.byteArrayViewVarHandle(short[].class, ByteOrder.BIG_ENDIAN);
/**
* A {@link VarHandle} to read/write big endian {@code int} from a byte array. Shape: {@code int
* vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, int val)}
*
* @deprecated Better use little endian unless it is needed for backwards compatibility.
*/
@Deprecated
public static final VarHandle VH_BE_INT =
MethodHandles.byteArrayViewVarHandle(int[].class, ByteOrder.BIG_ENDIAN);
/**
* A {@link VarHandle} to read/write big endian {@code long} from a byte array. Shape: {@code long
* vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, long val)}
*
* @deprecated Better use little endian unless it is needed for backwards compatibility.
*/
@Deprecated
public static final VarHandle VH_BE_LONG =
MethodHandles.byteArrayViewVarHandle(long[].class, ByteOrder.BIG_ENDIAN);
/**
* A {@link VarHandle} to read/write big endian {@code float} from a byte array. Shape: {@code
* float vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, float val)}
*
* @deprecated Better use little endian unless it is needed for backwards compatibility.
*/
@Deprecated
public static final VarHandle VH_BE_FLOAT =
MethodHandles.byteArrayViewVarHandle(float[].class, ByteOrder.BIG_ENDIAN);
/**
* A {@link VarHandle} to read/write big endian {@code double} from a byte array. Shape: {@code
* double vh.get(byte[] arr, int ofs)} and {@code void vh.set(byte[] arr, int ofs, double val)}
*
* @deprecated Better use little endian unless it is needed for backwards compatibility.
*/
@Deprecated
public static final VarHandle VH_BE_DOUBLE =
MethodHandles.byteArrayViewVarHandle(double[].class, ByteOrder.BIG_ENDIAN);
/**
* returns the next highest power of two, or the current value if it's already a power of two or
* zero
*/
public static int nextHighestPowerOfTwo(int v) {
v--;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v++;
return v;
}
/**
* returns the next highest power of two, or the current value if it's already a power of two or
* zero
*/
public static long nextHighestPowerOfTwo(long v) {
v--;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v |= v >> 32;
v++;
return v;
}
// magic numbers for bit interleaving
private static final long MAGIC0 = 0x5555555555555555L;
private static final long MAGIC1 = 0x3333333333333333L;
private static final long MAGIC2 = 0x0F0F0F0F0F0F0F0FL;
private static final long MAGIC3 = 0x00FF00FF00FF00FFL;
private static final long MAGIC4 = 0x0000FFFF0000FFFFL;
private static final long MAGIC5 = 0x00000000FFFFFFFFL;
private static final long MAGIC6 = 0xAAAAAAAAAAAAAAAAL;
// shift values for bit interleaving
private static final long SHIFT0 = 1;
private static final long SHIFT1 = 2;
private static final long SHIFT2 = 4;
private static final long SHIFT3 = 8;
private static final long SHIFT4 = 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 << SHIFT4)) & MAGIC4;
v1 = (v1 | (v1 << SHIFT3)) & MAGIC3;
v1 = (v1 | (v1 << SHIFT2)) & MAGIC2;
v1 = (v1 | (v1 << SHIFT1)) & MAGIC1;
v1 = (v1 | (v1 << SHIFT0)) & MAGIC0;
v2 = (v2 | (v2 << SHIFT4)) & MAGIC4;
v2 = (v2 | (v2 << SHIFT3)) & MAGIC3;
v2 = (v2 | (v2 << SHIFT2)) & MAGIC2;
v2 = (v2 | (v2 << SHIFT1)) & MAGIC1;
v2 = (v2 | (v2 << SHIFT0)) & MAGIC0;
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 &= MAGIC0;
b = (b ^ (b >>> SHIFT0)) & MAGIC1;
b = (b ^ (b >>> SHIFT1)) & MAGIC2;
b = (b ^ (b >>> SHIFT2)) & MAGIC3;
b = (b ^ (b >>> SHIFT3)) & MAGIC4;
b = (b ^ (b >>> SHIFT4)) & MAGIC5;
return b;
}
/** flip flops odd with even bits */
public static long flipFlop(final long b) {
return ((b & MAGIC6) >>> 1) | ((b & MAGIC0) << 1);
}
/** Same as {@link #zigZagEncode(long)} but on integers. */
public static int zigZagEncode(int i) {
return (i >> 31) ^ (i << 1);
}
/**
* Zig-zag encode
* the provided long. Assuming the input is a signed long whose absolute value can be stored on
* n bits, the returned value will be an unsigned long that can be stored on
* n+1 bits.
*/
public static long zigZagEncode(long l) {
return (l >> 63) ^ (l << 1);
}
/** Decode an int previously encoded with {@link #zigZagEncode(int)}. */
public static int zigZagDecode(int i) {
return ((i >>> 1) ^ -(i & 1));
}
/** Decode a long previously encoded with {@link #zigZagEncode(long)}. */
public static long zigZagDecode(long l) {
return ((l >>> 1) ^ -(l & 1));
}
/**
* Return true if, and only if, the provided integer - treated as an unsigned integer - is either
* 0 or a power of two.
*/
public static boolean isZeroOrPowerOfTwo(int x) {
return (x & (x - 1)) == 0;
}
}