Java BigInteger from Stream readBigInteger(ByteArrayInputStream bais)

Description

read Big Integer

License

Open Source License

Declaration

public static BigInteger readBigInteger(ByteArrayInputStream bais) 

Method Source Code

//package com.java2s;
//* Licensed Materials - Property of IBM, Miracle A/S, and            *

import java.io.ByteArrayInputStream;

import java.math.BigInteger;

public class Main {
    public static BigInteger readBigInteger(ByteArrayInputStream bais) {
        return new BigInteger(readData(bais));
    }//from   ww  w. java 2  s .c o  m

    public static byte[] readData(ByteArrayInputStream bais) {
        int len = getLength(bais);
        byte[] data = new byte[len];
        bais.read(data, 0, len);
        return data;
    }

    public static int getLength(ByteArrayInputStream bais) {
        int lowbyte = bais.read();
        if ((lowbyte & 128) == 0) {
            // MSB = 0
            return lowbyte;
        } else if ((lowbyte & 64) == 0) {
            // MSB = 10
            lowbyte -= 128;
            int highbyte = bais.read();
            return lowbyte + highbyte * 64;
        } else if ((lowbyte & 32) == 0) {
            // MSB = 110
            lowbyte -= 128 + 64;
            int midbyte = bais.read();
            int highbyte = bais.read();
            return lowbyte + midbyte * 32 + highbyte * 32 * 256;
        } else {
            throw new RuntimeException("Cannot parse length");
        }
    }
}

Related

1. readBigInteger(DataInputStream dis)
2. readBigInteger(InputStream input)
3. readBigInteger(int n, DataInput dis)
4. readLineAsBigInteger(BufferedReader br)