com.devskiller.friendly_id.BigIntegerPairing Maven / Gradle / Ivy
package com.devskiller.friendly_id;
import java.math.BigInteger;
import java.util.function.Function;
/**
* Basing on snippet published by drmalex07
*
* https://gist.github.com/drmalex07/9008c611ffde6cb2ef3a2db8668bc251
*/
class BigIntegerPairing {
private static final BigInteger HALF = BigInteger.ONE.shiftLeft(64); // 2^64
private static final BigInteger MAX_LONG = BigInteger.valueOf(Long.MAX_VALUE);
private static Function toUnsigned = value
-> value.signum() < 0 ? value.add(HALF) : value;
private static Function toSigned =
value -> MAX_LONG.compareTo(value) < 0 ? value.subtract(HALF) : value;
static BigInteger pair(BigInteger hi, BigInteger lo) {
BigInteger unsignedLo = toUnsigned.apply(lo);
BigInteger unsignedHi = toUnsigned.apply(hi);
return unsignedLo.add(unsignedHi.multiply(HALF));
}
static BigInteger[] unpair(BigInteger value) {
BigInteger[] parts = value.divideAndRemainder(HALF);
BigInteger signedHi = toSigned.apply(parts[0]);
BigInteger signedLo = toSigned.apply(parts[1]);
return new BigInteger[]{signedHi, signedLo};
}
}