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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;
import java.math.BigInteger;
import java.util.Arrays;
/**
* Helper APIs to encode numeric values as sortable bytes and vice-versa.
*
* To also index floating point numbers, this class supplies two methods to convert them to
* integer values by changing their bit layout: {@link #doubleToSortableLong}, {@link
* #floatToSortableInt}. You will have no precision loss by converting floating point numbers to
* integers and back (only that the integer form is not usable). Other data types like dates can
* easily converted to longs or ints (e.g. date to long: {@link java.util.Date#getTime}).
*
* @lucene.internal
*/
public final class NumericUtils {
private NumericUtils() {} // no instance!
/**
* Converts a double value to a sortable signed long. The value is
* converted by getting their IEEE 754 floating-point "double format" bit layout and
* then some bits are swapped, to be able to compare the result as long. By this the precision is
* not reduced, but the value can easily used as a long. The sort order (including {@link
* Double#NaN}) is defined by {@link Double#compareTo}; {@code NaN} is greater than positive
* infinity.
*
* @see #sortableLongToDouble
*/
public static long doubleToSortableLong(double value) {
return sortableDoubleBits(Double.doubleToLongBits(value));
}
/**
* Converts a sortable long back to a double.
*
* @see #doubleToSortableLong
*/
public static double sortableLongToDouble(long encoded) {
return Double.longBitsToDouble(sortableDoubleBits(encoded));
}
/**
* Converts a float value to a sortable signed int. The value is
* converted by getting their IEEE 754 floating-point "float format" bit layout and then
* some bits are swapped, to be able to compare the result as int. By this the precision is not
* reduced, but the value can easily used as an int. The sort order (including {@link Float#NaN})
* is defined by {@link Float#compareTo}; {@code NaN} is greater than positive infinity.
*
* @see #sortableIntToFloat
*/
public static int floatToSortableInt(float value) {
return sortableFloatBits(Float.floatToIntBits(value));
}
/**
* Converts a sortable int back to a float.
*
* @see #floatToSortableInt
*/
public static float sortableIntToFloat(int encoded) {
return Float.intBitsToFloat(sortableFloatBits(encoded));
}
/** Converts IEEE 754 representation of a double to sortable order (or back to the original) */
public static long sortableDoubleBits(long bits) {
return bits ^ (bits >> 63) & 0x7fffffffffffffffL;
}
/** Converts IEEE 754 representation of a float to sortable order (or back to the original) */
public static int sortableFloatBits(int bits) {
return bits ^ (bits >> 31) & 0x7fffffff;
}
/** Result = a - b, where a >= b, else {@code IllegalArgumentException} is thrown. */
public static void subtract(int bytesPerDim, int dim, byte[] a, byte[] b, byte[] result) {
int start = dim * bytesPerDim;
int end = start + bytesPerDim;
int borrow = 0;
for (int i = end - 1; i >= start; i--) {
int diff = (a[i] & 0xff) - (b[i] & 0xff) - borrow;
if (diff < 0) {
diff += 256;
borrow = 1;
} else {
borrow = 0;
}
result[i - start] = (byte) diff;
}
if (borrow != 0) {
throw new IllegalArgumentException("a < b");
}
}
/**
* Result = a + b, where a and b are unsigned. If there is an overflow, {@code
* IllegalArgumentException} is thrown.
*/
public static void add(int bytesPerDim, int dim, byte[] a, byte[] b, byte[] result) {
int start = dim * bytesPerDim;
int end = start + bytesPerDim;
int carry = 0;
for (int i = end - 1; i >= start; i--) {
int digitSum = (a[i] & 0xff) + (b[i] & 0xff) + carry;
if (digitSum > 255) {
digitSum -= 256;
carry = 1;
} else {
carry = 0;
}
result[i - start] = (byte) digitSum;
}
if (carry != 0) {
throw new IllegalArgumentException("a + b overflows bytesPerDim=" + bytesPerDim);
}
}
/**
* Encodes an integer {@code value} such that unsigned byte order comparison is consistent with
* {@link Integer#compare(int, int)}
*
* @see #sortableBytesToInt(byte[], int)
*/
public static void intToSortableBytes(int value, byte[] result, int offset) {
// Flip the sign bit, so negative ints sort before positive ints correctly:
value ^= 0x80000000;
BitUtil.VH_BE_INT.set(result, offset, value);
}
/**
* Decodes an integer value previously written with {@link #intToSortableBytes}
*
* @see #intToSortableBytes(int, byte[], int)
*/
public static int sortableBytesToInt(byte[] encoded, int offset) {
int x = (int) BitUtil.VH_BE_INT.get(encoded, offset);
// Re-flip the sign bit to restore the original value:
return x ^ 0x80000000;
}
/**
* Encodes an long {@code value} such that unsigned byte order comparison is consistent with
* {@link Long#compare(long, long)}
*
* @see #sortableBytesToLong(byte[], int)
*/
public static void longToSortableBytes(long value, byte[] result, int offset) {
// Flip the sign bit so negative longs sort before positive longs:
value ^= 0x8000000000000000L;
BitUtil.VH_BE_LONG.set(result, offset, value);
}
/**
* Decodes a long value previously written with {@link #longToSortableBytes}
*
* @see #longToSortableBytes(long, byte[], int)
*/
public static long sortableBytesToLong(byte[] encoded, int offset) {
long v = (long) BitUtil.VH_BE_LONG.get(encoded, offset);
// Flip the sign bit back
v ^= 0x8000000000000000L;
return v;
}
/**
* Encodes a BigInteger {@code value} such that unsigned byte order comparison is consistent with
* {@link BigInteger#compareTo(BigInteger)}. This also sign-extends the value to {@code
* bigIntSize} bytes if necessary: useful to create a fixed-width size.
*
* @see #sortableBytesToBigInt(byte[], int, int)
*/
public static void bigIntToSortableBytes(
BigInteger bigInt, int bigIntSize, byte[] result, int offset) {
byte[] bigIntBytes = bigInt.toByteArray();
byte[] fullBigIntBytes;
if (bigIntBytes.length < bigIntSize) {
fullBigIntBytes = new byte[bigIntSize];
System.arraycopy(
bigIntBytes, 0, fullBigIntBytes, bigIntSize - bigIntBytes.length, bigIntBytes.length);
if ((bigIntBytes[0] & 0x80) != 0) {
// sign extend
Arrays.fill(fullBigIntBytes, 0, bigIntSize - bigIntBytes.length, (byte) 0xff);
}
} else if (bigIntBytes.length == bigIntSize) {
fullBigIntBytes = bigIntBytes;
} else {
throw new IllegalArgumentException(
"BigInteger: " + bigInt + " requires more than " + bigIntSize + " bytes storage");
}
// Flip the sign bit so negative bigints sort before positive bigints:
fullBigIntBytes[0] ^= 0x80;
System.arraycopy(fullBigIntBytes, 0, result, offset, bigIntSize);
assert sortableBytesToBigInt(result, offset, bigIntSize).equals(bigInt)
: "bigInt=" + bigInt + " converted=" + sortableBytesToBigInt(result, offset, bigIntSize);
}
/**
* Decodes a BigInteger value previously written with {@link #bigIntToSortableBytes}
*
* @see #bigIntToSortableBytes(BigInteger, int, byte[], int)
*/
public static BigInteger sortableBytesToBigInt(byte[] encoded, int offset, int length) {
byte[] bigIntBytes = new byte[length];
System.arraycopy(encoded, offset, bigIntBytes, 0, length);
// Flip the sign bit back to the original
bigIntBytes[0] ^= 0x80;
return new BigInteger(bigIntBytes);
}
}