Hex.java

package org.eclipse.jetty.servlets.gzip;

public final class Hex
{
    private static final char[] hexcodes = "0123456789abcdef".toCharArray();

    public static byte[] asByteArray(String id, int size)
    {
        if ((id.length() < 0) || (id.length() > (size * 2)))
        {
            throw new IllegalArgumentException(String.format("Invalid ID length of <%d> expected range of <0> to <%d>",id.length(),(size * 2)));
        }

        byte buf[] = new byte[size];
        byte hex;
        int len = id.length();

        int idx = (int)Math.floor(((size * 2) - (double)len) / 2);
        int i = 0;
        if ((len % 2) != 0)
        { // deal with odd numbered chars
            i -= 1;
        }

        for (; i < len; i++)
        {
            hex = 0;
            if (i >= 0)
            {
                hex = (byte)(Character.digit(id.charAt(i),16) << 4);
            }
            i++;
            hex += (byte)(Character.digit(id.charAt(i),16));

            buf[idx] = hex;
            idx++;
        }

        return buf;
    }

    public static String asHex(byte buf[])
    {
        int len = buf.length;
        char out[] = new char[len * 2];
        for (int i = 0; i < len; i++)
        {
            out[i * 2] = hexcodes[(buf[i] & 0xF0) >> 4];
            out[(i * 2) + 1] = hexcodes[(buf[i] & 0x0F)];
        }
        return String.valueOf(out);
    }

    private Hex()
    {
        /* prevent instantiation */
    }
}