How do I decode a string from base 32 to a BigInteger

Question

I tried the following code:

import java.math.BigInteger;
import org.apache.commons.codec.binary.Base32;
import org.junit.Test;

public class Sandbox
{
  @Test
  public void testSomething() {
    String sInput = "GIYTINZUHAZTMNBX";

    BigInteger bb = new BigInteger(new Base32().decode(sInput));

    System.out.println("number = " + bb);
  }
}

and heres the output:

number = 237025977136523702055991

using this website to convert between base 32 I get a different result than the actual output. Heres the result I expect to see based on what I got from the website:

expected output = 2147483647

Any idea why this is happening?

Edit:

Forgive me for making it confusing by purposefully attempting to convert 2^31-1.

Using the conversion website I linked to earlier, I changed the input:

String sInput = "GE4DE===";

Expected output:

number = 182

Actual output:

number = 3225650

Answer 1

What you're doing is correct... assuming that the Base32 string comes from Base32-encoding a byte array you get from calling BigInteger.toByteArray().

BigInteger(byte[] val) does not really take an array of arbitrary bytes. It takes the byte[] representation of a BigInteger. Also, it assumes the most-significant byte is in val[0]).

Answer 2

If it's base-32 the X, Y, and Z shouldn't be there. Are you sure it isn't base-36?