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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.jackrabbit.oak.commons;
import java.util.Arrays;
import java.util.Date;
public final class LongUtils {
private LongUtils() {}
/**
* Sums {@code a} and {@code b} and verifies that it doesn't overflow in
* signed long arithmetic, in which case {@link Long#MAX_VALUE} will be
* returned instead of the result.
*
* Note: this method is a variant of {@link org.apache.jackrabbit.guava.common.math.LongMath#checkedAdd(long, long)}
* that returns {@link Long#MAX_VALUE} instead of throwing {@code ArithmeticException}.
*
* @see org.apache.jackrabbit.guava.common.math.LongMath#checkedAdd(long, long)
*/
public static long safeAdd(long a, long b) {
long result = a + b;
if ((a ^ b) < 0 | (a ^ result) >= 0) {
return result;
} else {
return Long.MAX_VALUE;
}
}
/**
* Calculate an expiration time based on {@code new Date().getTime()} and
* the specified {@code expiration} in number of milliseconds.
*
* @param expiration The expiration in milliseconds.
* @return The expiration time.
*/
public static long calculateExpirationTime(long expiration) {
return LongUtils.safeAdd(expiration, new Date().getTime());
}
/*
* Taken from https://github.com/google/guava/blob/0c33dd12b193402cdf6962d43d69743521aa2f76/guava/src/com/google/common/primitives/Longs.java#L334
*/
private static final class AsciiDigits {
private AsciiDigits() {
}
private static final byte[] asciiDigits;
static {
byte[] result = new byte[128];
Arrays.fill(result, (byte) -1);
for (int i = 0; i < 10; i++) {
result['0' + i] = (byte) i;
}
for (int i = 0; i < 26; i++) {
result['A' + i] = (byte) (10 + i);
result['a' + i] = (byte) (10 + i);
}
asciiDigits = result;
}
static int digit(char c) {
return (c < 128) ? asciiDigits[c] : -1;
}
}
private static final int RADIX = 10;
/**
* Parses the specified string as a signed decimal long value. Unlike {@link Long#parseLong(String)}, this method
* returns {@code null} instead of throwing an exception if parsing fails. This can be significantly more efficient
* when the string to be parsed is often invalid, as raising an exception is an expensive operation.
*
* This is a simplified version of
* Longs.tryParse()
* in Guava. This version is hardcoded to only support radix 10.
*
*
* @see org.apache.jackrabbit.guava.common.primitives.Longs#tryParse(String)
*/
public static Long tryParse(String string) {
if (string == null || string.isEmpty()) {
return null;
}
boolean negative = string.charAt(0) == '-';
int index = negative ? 1 : 0;
if (index == string.length()) {
return null;
}
int digit = AsciiDigits.digit(string.charAt(index++));
if (digit < 0 || digit >= RADIX) {
return null;
}
long accum = -digit;
long cap = Long.MIN_VALUE / RADIX;
while (index < string.length()) {
digit = AsciiDigits.digit(string.charAt(index++));
if (digit < 0 || digit >= RADIX || accum < cap) {
return null;
}
accum *= RADIX;
if (accum < Long.MIN_VALUE + digit) {
return null;
}
accum -= digit;
}
if (negative) {
return accum;
} else if (accum == Long.MIN_VALUE) {
return null;
} else {
return -accum;
}
}
}