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I have a array of raw bytes which i need to tokenize to a list of byte array in java. Explained better by the following method declaration. 

public static List<byte[]> splitMessage(byte[] rawByte, String tokenDelimiter)

Example runs.

Example Run 1:

Raw byte

byte[] rawBytes = new byte[]{72,118,121,49,85,118,97,113,111,124,44,124,49,48,43,57,48,36,63,49,66,70,22,18,124,44,124,23,27,25,54,24,24,34,44,57,69,66,49,47,66,16,39,35,32,36,30,50,63,124,44,124,16,18,24,64,4,94,124,44,124,19,31,42,55,66,46,34,62,34,37};

tokenDelimiter is |,| (i.e 124,44,124)

So the List returned is as:

Token 1: 72,118,121,49,85,118,97,113,111
Token 2: 49,48,43,57,48,36,63,49,66,70,22,18
Token 3: 23,27,25,54,24,24,34,44,57,69,66,49,47,66,16,39,35,32,36,30,50,63,
Token 4: 16,18,24,64,4,94
Token 5: 19,31,42,55,66,46,34,62,34,37

Example Run 2: 

byte[] rawBytes = new byte[]{72,118,121,49,85,118,97,113,111,124,44,124,49,48,43,57,48,36,63,49,66,70,22,18,124,44,124,124,44,124,23,27,25,54,24,24,34,44,57,69,66,49,47,66,16,39,35,32,36,30,50,63,124,44,124,16,18,24,64,4,94,124,44,124,19,31,42,55,66,46,34,62,34,37,124,44,124,124,44,124};

tokenDelimiter is |,| (i.e 124,44,124) 

Token 1: 72,118,121,49,85,118,97,113,111
Token 2: 49,48,43,57,48,36,63,49,66,70,22,18
Token 3: <Empty>
Token 3: 23,27,25,54,24,24,34,44,57,69,66,49,47,66,16,39,35,32,36,30,50,63,
Token 4: 16,18,24,64,4,94
Token 5: 19,31,42,55,66,46,34,62,34,37
Token 6: <Empty>
Token 7: <Empty>

I am able to achive example run from following code snippet. But stuck with tags in the second one. 

public static List<byte[]> splitMessageSept19(byte[] rawByte, String tokenDelimiter) throws UnsupportedEncodingException
{
    List<byte[]> tokens = new ArrayList<byte[]>();

    final byte[] byteArray = tokenDelimiter.getBytes("UTF-8");
    final byte byteDelimitorFirstByte  = byteArray[0];

    int bytenum =0 ;
    int lastIndex = 0;
    int storIterator =0;
    for ( int iterator = 0 ; iterator <= rawByte.length ; iterator++ )
    {
        if (iterator == rawByte.length || rawByte[iterator] == byteDelimitorFirstByte)
        {
            storIterator = iterator;
            if ( iterator != rawByte.length )
            {
                for ( int i=0 ; i < byteArray.length ; i++ )
                {
                    if ( rawByte[iterator] == byteArray[i] )
                    {
                        iterator++ ;
                        continue;
                    }
                    else
                    {
                        break;
                    }
                }
            }
            byte[] byteArrayExtracted = new byte[storIterator - lastIndex];
            System.arraycopy(rawByte, lastIndex, byteArrayExtracted, 0, 
                             storIterator - lastIndex);
            lastIndex = iterator ;
            tokens.add(byteArrayExtracted);
            byteArrayExtracted = null;
        }
    }
    for ( byte[] bytetoken : tokens )
    {
        System.out.println("Token received is: " + new String(bytetoken, "UTF-8"));
    }
    return tokens;
}

Has anyone faced a similar problem of tokenizing arrays? Please suggest if there is some other way to tokenize arrays.

Please note: I don't want convert the byte stream to String, tokenize in String format and convert back to bytes. It may have its on problems of encoding.

Vikdor
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user813063
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2 Answers2

3

If you use ISO-8859-1 then bytes are preserved as they were originally.

private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");

public static List<byte[]> splitMessageSept19(byte[] rawByte, String tokenDelimiter) {
    Pattern pattern = Pattern.compile(tokenDelimiter, Pattern.LITERAL);
    String[] parts = pattern.split(new String(rawByte, ISO_8859_1), -1);
    List<byte[]> ret = new ArrayList<byte[]>();
    for (String part : parts) 
        ret.add(part.getBytes(ISO_8859_1));
    return ret;
}

public static void main(String... args) {
    StringBuilder sb = new StringBuilder();
    for(int i=0;i<256;i++)
        sb.append((char) i);
    byte[] bytes = sb.toString().getBytes(ISO_8859_1);
    List<byte[]> list = splitMessageSept19(bytes, ",");
    for (byte[] b : list) 
        System.out.println(Arrays.toString(b));
}

prints

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43] [45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, -128, -127, -126, -125, -124, -123, -122, -121, -120, -119, -118, -117, -116, -115, -114, -113, -112, -111, -110, -109, -108, -107, -106, -105, -104, -103, -102, -101, -100, -99, -98, -97, -96, -95, -94, -93, -92, -91, -90, -89, -88, -87, -86, -85, -84, -83, -82, -81, -80, -79, -78, -77, -76, -75, -74, -73, -72, -71, -70, -69, -68, -67, -66, -65, -64, -63, -62, -61, -60, -59, -58, -57, -56, -55, -54, -53, -52, -51, -50, -49, -48, -47, -46, -45, -44, -43, -42, -41, -40, -39, -38, -37, -36, -35, -34, -33, -32, -31, -30, -29, -28, -27, -26, -25, -24, -23, -22, -21, -20, -19, -18, -17, -16, -15, -14, -13, -12, -11, -10, -9, -8, -7, -6, -5, -4, -3, -2, -1]

Calling

byte[] rawBytes = new byte[]{72,118,121,49,85,118,97,113,111,124,44,124,49,48,43,57,48,36,63,49,66,70,22,18,124,44,124,124,44,124,23,27,25,54,24,24,34,44,57,69,66,49,47,66,16,39,35,32,36,30,50,63,124,44,124,16,18,24,64,4,94,124,44,124,19,31,42,55,66,46,34,62,34,37,124,44,124,124,44,124};
List<byte[]> list = splitMessageSept19(rawBytes, "|,|");

produces

[72, 118, 121, 49, 85, 118, 97, 113, 111]
[49, 48, 43, 57, 48, 36, 63, 49, 66, 70, 22, 18]
[]
[23, 27, 25, 54, 24, 24, 34, 44, 57, 69, 66, 49, 47, 66, 16, 39, 35, 32, 36, 30, 50, 63]
[16, 18, 24, 64, 4, 94]
[19, 31, 42, 55, 66, 46, 34, 62, 34, 37]
[]
[]
Peter Lawrey
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  • I was looking for an algorithm that don't convert the byte stream to String, tokenize in String format and convert back to bytes. As i was fearing that there would be encoding issues with it. I tried your solution and this doesn't give encoding issues. Thanks for the quick reply. – user813063 Sep 20 '12 at 06:59
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    The trick is to use `ISO-8859-1` encoding which just maps `n => n` provided `0 <= n <= 255`. – Peter Lawrey Sep 20 '12 at 07:13
0

You should take a look at the KMP algorithm: KMP on wikipedia and other string search algorithms as well.

As a quick fix to your code try this:

public static List<byte[]> splitMessageSept19(byte[] rawByte, String tokenDelimiter) throws UnsupportedEncodingException
{
    List<byte[]> tokens = new ArrayList<byte[]>();

    final byte[] byteArray = tokenDelimiter.getBytes("UTF-8");
    int lastIndex = 0;

    for (int iterator = 0; iterator < rawByte.length - byteArray.length + 1; )
    {
        boolean patternFound = true;
        for (int i = 0; i < byteArray.length; i++)
        {
            if (rawByte[iterator + i] != byteArray[i])
            {
                patternFound = false;
                break;
            }
        }
        if (patternFound)
        {
            byte[] byteArrayExtracted = new byte[iterator - lastIndex];
            System.arraycopy(rawByte, lastIndex, byteArrayExtracted, 0, iterator - lastIndex);
            iterator += byteArray.length;
            lastIndex = iterator;
            tokens.add(byteArrayExtracted);
        }
        else
            iterator++;

    }
    for (byte[] bytetoken : tokens)
    {
        System.out.println("Token received is: " + new String(bytetoken, "UTF-8"));
    }
    return tokens;
}

I haven't compiled this code so it might be broken, but even though I hope you get the idea.

This is a naive algorithm which is pretty slow especially if the delimiter is long. If you want something better go take a look at some other string search algorithms.

ciamej
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