java encoding sniffer

package my;

import java.io.File;

public class Encoding {

     /**************************************************************
     * http://en.wikipedia.org/wiki/Cp1252#Codepage_layout         *
     * http://en.wikipedia.org/wiki/ISO/IEC_8859-1#Codepage_layout *
     * http://en.wikipedia.org/wiki/Utf-8#Codepage_layout          *
     **************************************************************/

     /***********************************************************************************
     *  UTF-8 patterns                                                                  *
     *  http://triptico.com/docs/unicode.html                                           *
     *  U+00000000 - U+0000007F: 0xxxxxxx                                               *
     *  U+00000080 - U+000007FF: 110xxxxx 10xxxxxx                                      *
     *  U+00000800 - U+0000FFFF: 1110xxxx 10xxxxxx 10xxxxxx                             *
     *  U+00010000 - U+001FFFFF: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx                    *
     *  U+00200000 - U+03FFFFFF: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx           *
     *  U+04000000 - U+7FFFFFFF: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx  *
     ***********************************************************************************/

    /**
     * Nota bene: byte e' signed, quindi per caratteri > 128 considerare che il valore sara' negativo
     */

    public static void main(String[] args) throws Exception {
        String[] files = new File("input").list();
        for (int i=0;i<files.length;i++) {
            String fileName = "input/" + files[i];

            System.out.println("fileName: " + fileName);
            System.out.println("encoding: "+guessEncoding(IO.readFile(fileName)));
        }
    }
    // java coi byte signed nun se po vede
    public static String guessEncoding(byte[] blob) {
        if (blob.length > 2) {
            if (blob[0] == (byte)0xEF && blob[1] == (byte)0xBB && blob[2] == (byte)0xBF) {
                // bom utf-8 presente
                return "UTF-8";
            }
        }
        boolean excludeCp1252 = false;
        boolean excludeLatin1 = false;
        boolean validUtf8Sequence = false;
        boolean isUtf8Sequence = false;
        boolean containsUtf8Sequences = false;
        boolean latin1GrayArea = false;

        for (int i = 0; i < blob.length; i++) {
            byte b = blob[i];

            if (b == (byte)0x7F || b >= (byte)0x80 && b <= (byte)0xA0) {
                // non e' latin1
                excludeLatin1 = true;
            }
            if (b == (byte)0x81 || b == (byte)0x8D || b == (byte)0x8F || b == (byte)0x90 || b == (byte)0x9D) {
                // non e' cp1252
                excludeCp1252 = true;
            }

            if (b >= B10000000 && b <= B10111111) {
                latin1GrayArea = true;
            }
            isUtf8Sequence = false;
            validUtf8Sequence = false;
            if (b >= B11000000 && b <= B11011111) {
                // utf8: U+00000080 - U+000007FF
                isUtf8Sequence = true;
                validUtf8Sequence = i < blob.length - 1
                                    && blob[i+1] >= B10000000 && blob[i+1] <= B10111111;
                if (validUtf8Sequence) i+=1;
            } else if (b >= B11100000 && b <= B11101111) {
                // utf8: U+00000800 - U+0000FFFF
                isUtf8Sequence = true;
                validUtf8Sequence = i < blob.length - 2
                                    && blob[i+1] >= B10000000 && blob[i+1] <= B10111111
                                    && blob[i+2] >= B10000000 && blob[i+2] <= B10111111;
                if (validUtf8Sequence) i+=2;
            } else if (b >= B11110000 && b <= B11110111) {
                // utf-8: U+00010000 - U+001FFFFF
                isUtf8Sequence = true;
                validUtf8Sequence = i < blob.length - 3
                                    && blob[i+1] >= B10000000 && blob[i+1] <= B10111111
                                    && blob[i+2] >= B10000000 && blob[i+2] <= B10111111
                                    && blob[i+3] >= B10000000 && blob[i+3] <= B10111111;
                if (validUtf8Sequence) i+=3;
            } else if (b >= B11111000 && b <= B11111011) {
                // utf-8: U+00200000 - U+03FFFFFF
                isUtf8Sequence = true;
                validUtf8Sequence = i < blob.length - 4
                                    && blob[i+1] >= B10000000 && blob[i+1] <= B10111111
                                    && blob[i+2] >= B10000000 && blob[i+2] <= B10111111
                                    && blob[i+3] >= B10000000 && blob[i+3] <= B10111111
                                    && blob[i+4] >= B10000000 && blob[i+4] <= B10111111;
                if (validUtf8Sequence) i+=4;
            } else if (b == B11111100 || b == B11111101) {
                // utf-8: U+04000000 - U+7FFFFFFF
                isUtf8Sequence = true;
                validUtf8Sequence = i < blob.length - 5
                                    && blob[i+1] >= B10000000 && blob[i+1] <= B10111111
                                    && blob[i+2] >= B10000000 && blob[i+2] <= B10111111
                                    && blob[i+3] >= B10000000 && blob[i+3] <= B10111111
                                    && blob[i+4] >= B10000000 && blob[i+4] <= B10111111
                                    && blob[i+5] >= B10000000 && blob[i+5] <= B10111111;
                if (validUtf8Sequence) i+=5;
            }
            if (excludeCp1252 && excludeLatin1) {
                if (isUtf8Sequence && !validUtf8Sequence) {
                    return null;
                }
            }
            containsUtf8Sequences = containsUtf8Sequences || (isUtf8Sequence && validUtf8Sequence);
        }

        if (excludeCp1252 && !containsUtf8Sequences) {
            return "latin1";
        }
        if (excludeLatin1 && !containsUtf8Sequences) {
            return "cp1252";
        }
        if (!excludeLatin1 && !excludeCp1252 && latin1GrayArea && !containsUtf8Sequences) {
            return "latin1";
        }
        return "UTF-8";
    }

    private static byte B11000000 = fromBin("11000000");
    private static byte B11011111 = fromBin("11011111");

    private static byte B11100000 = fromBin("11100000");
    private static byte B11101111 = fromBin("11101111");

    private static byte B11110000 = fromBin("11110000");
    private static byte B11110111 = fromBin("11110111");

    private static byte B11111000 = fromBin("11111000");
    private static byte B11111011 = fromBin("11111011");

    private static byte B11111100 = fromBin("11111100");
    private static byte B11111101 = fromBin("11111101");

    private static byte B10000000 = fromBin("10000000");
    private static byte B10111111 = fromBin("10111111");

    public static byte fromBin(String bin) {
        return (byte) Integer.parseInt(bin, 2);
    }
}