Java BigInteger Calculate uint64ToByteStreamLE(BigInteger val, OutputStream stream)

Description

uint To Byte Stream LE

License

Apache License

Declaration

public static void uint64ToByteStreamLE(BigInteger val, OutputStream stream) throws IOException 

Method Source Code

//package com.java2s;
/**//from   ww w .  ja  v a  2 s.  com
 * Copyright 2011 Google Inc.
 *
 * 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.
 */

import java.io.IOException;
import java.io.OutputStream;

import java.math.BigInteger;

public class Main {
    public static void uint64ToByteStreamLE(BigInteger val, OutputStream stream) throws IOException {
        byte[] bytes = val.toByteArray();
        if (bytes.length > 8) {
            throw new RuntimeException("Input too large to encode into a uint64");
        }
        bytes = reverseBytes(bytes);
        stream.write(bytes);
        if (bytes.length < 8) {
            for (int i = 0; i < 8 - bytes.length; i++)
                stream.write(0);
        }
    }

    /**
     * Returns a copy of the given byte array in reverse order.
     */
    public static byte[] reverseBytes(byte[] bytes) {
        // We could use the XOR trick here but it's easier to understand if we don't. If we find this is really a
        // performance issue the matter can be revisited.
        byte[] buf = new byte[bytes.length];
        for (int i = 0; i < bytes.length; i++)
            buf[i] = bytes[bytes.length - 1 - i];
        return buf;
    }
}

Related

1. sumOfDigits(BigInteger ab)
2. sumOfDigits(BigInteger n)
3. trim(BigInteger bi)
4. trim(BigInteger n)
5. trimToPrecision(BigInteger number, int precision)
6. unsignedBigIntergerToByteArray(BigInteger bigInteger)
7. unsignedLongToBigInteger(byte[] source)
8. unsignedToBigInteger(long l)
9. writeBigInteger(BigInteger integer, DataOutputStream out)