com.arangodb.velocypack.internal.util.NumberUtil Maven / Gradle / Ivy
/*
* DISCLAIMER
*
* Copyright 2016 ArangoDB GmbH, Cologne, Germany
*
* Licensed 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.
*
* Copyright holder is ArangoDB GmbH, Cologne, Germany
*/
package com.arangodb.velocypack.internal.util;
import java.math.BigInteger;
/**
* @author Mark Vollmary
*
*/
public class NumberUtil {
private static final int DOUBLE_BYTES = Double.SIZE / Byte.SIZE;
private static final int LONG_BYTES = Long.SIZE / Byte.SIZE;
private NumberUtil() {
super();
}
public static double toDouble(final byte[] array, final int offset, final int length) {
return Double.longBitsToDouble(toLong(array, offset, DOUBLE_BYTES));
}
public static long toLong(final byte[] array, final int offset, final int length) {
return toLong(array, offset, length, false);
}
public static long toLong(final byte[] array, final int offset, final int length, final boolean fillNegativeBytes) {
long result = 0;
if (fillNegativeBytes && length < LONG_BYTES && array[(offset + length - 1)] <= (byte) -1) {
for (int i = 0; i <= 8 - length; i++) {
result <<= LONG_BYTES;
result |= ((byte) -1 & 0xFF);
}
}
for (int i = (offset + length - 1); i >= offset; i--) {
result <<= LONG_BYTES;
result |= (array[i] & 0xFF);
}
return result;
}
public static BigInteger toBigInteger(final byte[] array, final int offset, final int length) {
BigInteger result = new BigInteger(1, new byte[] {});
for (int i = (offset + length - 1); i >= offset; i--) {
result = result.shiftLeft(LONG_BYTES);
result = result.or(BigInteger.valueOf(array[i] & 0xFF));
}
return result;
}
/**
* read a variable length integer in unsigned LEB128 format
*/
public static long readVariableValueLength(final byte[] array, final int offset, final boolean reverse) {
long len = 0;
byte v;
long p = 0;
int i = offset;
do {
v = array[i];
len += ((long) (v & (byte) 0x7f)) << p;
p += 7;
if (reverse) {
--i;
} else {
++i;
}
} while ((v & (byte) 0x80) != 0);
return len;
}
/**
* calculate the length of a variable length integer in unsigned LEB128 format
*/
public static long getVariableValueLength(final long value) {
long len = 1;
long val = value;
while (val >= 0x80) {
val >>= 7;
++len;
}
return len;
}
}