Convert this line of Java code to C# code

Question

I need this line of Java code:

Integer.toString(256 + (0xFF & arrayOfByte[i]), 16).substring(1)

converted to C# since I'm not sure how to work with "0xFF".

EDIT This is the full code:

MessageDigest localMessageDigest = MessageDigest.getInstance("SHA-256");
      localMessageDigest.update(String.format(Locale.US, "%s:%s", new Object[] { paramString1, paramString2 }).getBytes());
      byte[] arrayOfByte = localMessageDigest.digest();
      StringBuffer localStringBuffer = new StringBuffer();
      for (int i = 0; ; i++)
      {
        if (i >= arrayOfByte.length)
          return localStringBuffer.toString();
        localStringBuffer.append(Integer.toString(256 + (0xFF & arrayOfByte[i]), 16).substring(1));
      }

It should just be 0xFF as AFAIK it's too small and doesn't have MSB set so shouldn't encounter any need for unchecked. — nanofarad
– nanofarad, Commented Jul 14, 2013 at 1:07
Are you at least able to follow the code. You'd see that 0xFF is a mask for whatever is in arrayOfByte[i]. Unless what's in the array is larger than a byte I don't see the reason to use it. — asafreedman
– asafreedman, Commented Jul 14, 2013 at 1:10
I updated it...maybe it will make more sense in the context of the whole code snippet — blizz
– blizz, Commented Jul 14, 2013 at 1:20
I'm betting the 0xFF is doing some implicit casting since 0xFF is probably treated as an int. I'm almost certain you could change that 0xFF to -1 and get the same result. — asafreedman
– asafreedman, Commented Jul 14, 2013 at 1:24
@asafreedman - In the big picture, you are correct. But (0xFF & arrayOfByte[i]) and (-1 & arrayOfByte[i]) are not the same. — Stephen C
– Stephen C, Commented Jul 14, 2013 at 1:43

Chase · Accepted Answer · 2013-07-14 01:42:27Z

7

On that note, the actual way you can do this in C# is as follows.

String.Format("{0:x2}", arrayOfByte[i]);

Which is very similar to the Java

String.format("%02x", arrayOfByte[i]);

Which is a simpler way to do what they are doing above.

answered Jul 14, 2013 at 1:42

Chase

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Stephen C · Accepted Answer · 2013-07-14 03:51:54Z

1

That Java expression is converting a signed byte to unsigned and then to hexadecimal with zero fill.

You should be able to code that in C#.

FWIW, the Java code gives the same answer as this:

  Integer.toString(256 + arrayOfByte[i], 16).substring(1)

or

  String.format("%02x", arrayOfByte[i])

Here's how the original works. The subexpression

  (0xFF & arrayOfByte[i])

is equivalent to

  (0xFF & ((int) arrayOfByte[i]))

which converts a signed byte (-128 to +127) to an unsigned byte (0 to +255). The purpose of the magic 256 + in the original is to ensure that the result of toString will be 3 hex digits long. Finally, the leading digit is removed, leaving you with a zero padded 2 digit hex number.

edited Jul 14, 2013 at 3:51

answered Jul 14, 2013 at 1:29

Stephen C

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1 Comment

Chase Over a year ago

Also gives the same answer as this. String.format("%02x",arrayOfByte[i])

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