bytes to hex string

, ,
1

Hi,

I need to pass an attachment into an ABAP RFC and need to change the bytes into a hex string. I have a small java routine to do this. However it takes 5 minutes to convert 245kb of data.

This seems very slow. Any guidance on how this conversion can be done quickly as I have to convert up to 5Mb of data.

Thanks in anticipation:eek:

2

Can you post your Java service? Perhaps there is something there that can be tweaked.

3

I have an input byte array bytes

Create a BigInteger using the byte array
BigInteger bi = new BigInteger(bytes);

String s = bi.toString(16);
if (s.length() % 2 != 0) {

}

4

I have an input byte array “bytes”

Create a BigInteger using the byte array
BigInteger bi = new BigInteger(bytes);

String s = bi.toString(16);
if (s.length() % 2 != 0) {
//Pad with 0
s + “0”+s;
}

I now split the byte array up into smaller chunks before converting and this has speeded things up a bit.
I also have the problem that my JPG file is creating a negative BigInteger and this is giving me a “0-” start to my hex string which I don’t quite understand

5

Not sure if this is what you need, but a book I bought recently had this class as part of a utilities package.

Mark

[highlight=java]
public class Utils
{
private static String digits = “0123456789abcdef”;

/**
 * Return length many bytes of the passed in byte array as a hex string.
 * 
 * @param data the bytes to be converted.
 * @param length the number of bytes in the data block to be converted.
 * @return a hex representation of length bytes of data.
 */
public static String toHex(byte[] data, int length)
{
    StringBuffer    buf = new StringBuffer();
    
    for (int i = 0; i != length; i++)
    {
        int    v = data[i] & 0xff;
        
        buf.append(digits.charAt(v >> 4));
        buf.append(digits.charAt(v & 0xf));
    }
    
    return buf.toString();
}

/**
 * Return the passed in byte array as a hex string.
 * 
 * @param data the bytes to be converted.
 * @return a hex representation of data.
 */
public static String toHex(byte[] data)
{
    return toHex(data, data.length);
}

}

[/highlight]

6

Mark beat me to the punch. The utils he posted are the way to go. String operations are notoriously inefficient, since String objects are immutable there’s a lot of time spent allocating objects. Using the “+” operator creates new String objects

Give the code Mark posted a try. You should see some good gains, though probably not 5 minutes worth.

7

Thanks guys great help.

I have one remaining problem.

What is the best way to do the opposite, i.e. change data from a hexstring to bytes. I was going to use BigInteger again?