Java BigInteger Calculate writeBigInteger(OutputStream output, BigInteger value)

Description

Write the arbitrarily sized signed BigInteger in vint format.

License

Apache License

Parameter

Parameter	Description
output	the stream to write to
value	the value to output

Exception

Parameter	Description
IOException	an exception

Declaration

static void writeBigInteger(OutputStream output, BigInteger value) throws IOException 

Method Source Code

//package com.java2s;
/**/*from   ww  w. j  ava2s .  c  o  m*/
 * 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.
 */

import java.io.IOException;

import java.io.OutputStream;
import java.math.BigInteger;

public class Main {
    /**
     * Write the arbitrarily sized signed BigInteger in vint format.
     *
     * Signed integers are encoded using the low bit as the sign bit using zigzag
     * encoding.
     *
     * Each byte uses the low 7 bits for data and the high bit for stop/continue.
     *
     * Bytes are stored LSB first.
     * @param output the stream to write to
     * @param value the value to output
     * @throws IOException
     */
    static void writeBigInteger(OutputStream output, BigInteger value) throws IOException {
        // encode the signed number as a positive integer
        value = value.shiftLeft(1);
        int sign = value.signum();
        if (sign < 0) {
            value = value.negate();
            value = value.subtract(BigInteger.ONE);
        }
        int length = value.bitLength();
        while (true) {
            long lowBits = value.longValue() & 0x7fffffffffffffffL;
            length -= 63;
            // write out the next 63 bits worth of data
            for (int i = 0; i < 9; ++i) {
                // if this is the last byte, leave the high bit off
                if (length <= 0 && (lowBits & ~0x7f) == 0) {
                    output.write((byte) lowBits);
                    return;
                } else {
                    output.write((byte) (0x80 | (lowBits & 0x7f)));
                    lowBits >>>= 7;
                }
            }
            value = value.shiftRight(63);
        }
    }
}

Related

1. unsignedToBigInteger(long l)
2. writeBigInteger(BigInteger integer, DataOutputStream out)
3. writeBigInteger(BigInteger m, int n, OutputStream os)
4. writeBigInteger(ByteArrayOutputStream baos, BigInteger bi)
5. writeBigInteger(ByteArrayOutputStream stream, BigInteger num)
6. writeField(String tagName, BigInteger value, PrintWriter writer, int indent)
7. writeLuposBigInteger(final BigInteger value, final int numberOfBits, final OutputStream os)
8. writeMPI(BigInteger num, OutputStream out)