IO-Link CRC32 implementation

0
votes

currently I try to implement the CRC32 check algorithm from IO-Link for IODD files in Java [1]. In IO-Link each sensor is described with an IODD xml file [2]. The file contains a stamp tag with a crc code. My problem here is that the algorithm uses only unsigned integers and Java does not uses this type of types. Is there still a way to implement that?

I also use JetBrains dotPeek program to decompile the IODDChecker (latest Version). The CRC-Logic is in the file clsCRC.cs. At the end of the file I found the method "CRC32" which calculates the CRC. The problem is that they use other integers (unsigned integers) for the lookup-table. An interesting fact is that the algorithm in the IODD checker (crc32_octetwise) is slightly different from the one described in the specification.

Hope you can help me :)

What I tested:

  • Java CRC32 from zip
  • Guava UnsignedInteger
  • BigInteger
  • long instead of int

Procedure:

  1. Program read the IODD as String/byte array
  2. Remove the CRC value from Stamp-Tag from the String/byte array
  3. Create CRC32 from string/byte array
  4. In the test IODD you can find the CRC 1195433981 which should be equal to the output of the algorithm

Algorithms:
There are two algorithms. The first one is bitwise and the second one is octetwise and uses an lookup-table which you can find here [2].

uint32_t crc32_bitwise(char *data, size_t length, uint32_t previousCrc32 = 1)
{
    uint32_t crc = ~previousCrc32;
    int j;
    const uint8_t* current = (const uint8_t*) data;
    while (length-- > 0)
    {
        crc ^= *current++;
        for (j = 0; j < 8; j++)
        {
            crc = (crc >> 1) ^ (-(int32_t)(crc & 1) & 0xEB31D82E);
        }
    }
    return ~crc;
}

uint32_t crc32_octetwise(uint8_t const * current, uint32_t length, uint32_t previousCrc32 = 1, const uint32_t crc32Lookup[256])
{
    uint32_t crc = ~previousCrc32;
    while (length-- > 0)
        crc = (crc >> 8) ^ crc32Lookup[(crc & 0xFF) ^ *current++];
    return ~crc;
}

[1] https://io-link.com/share/Downloads/Profiles/IOL-Profile_Firmware-Update_V11_10082_Sep19.zip
[2] https://ioddfinder.io-link.com/productvariants/search/11765
[3] Yet another Java CRC32 implementation related issue

Update 1

I forgot to add that I currently receive 1120211745 as CRC Code but 1195433981 is the correct code.

Update 2

The following Codes was implemented from me. The big arrays are the lookup tables. The first int array is the table from the [1] and the second one is the array from the decompiled source. In the original were the int numbers marked as unsigned (e.g. 1996959894U).

private static final int[] numArr1 = new int[] {
            0x00000000, 0x9695C4CA, 0xFB4839C9, 0x6DDDFD03, 0x20F3C3CF, 0xB6660705, 0xDBBBFA06, 0x4D2E3ECC, 0x41E7879E, 0xD7724354, 0xBAAFBE57, 0x2C3A7A9D, 0x61144451, 0xF781809B, 0x9A5C7D98, 0x0CC9B952, 0x83CF0F3C, 0x155ACBF6, 0x788736F5, 0xEE12F23F, 0xA33CCCF3, 0x35A90839, 0x5874F53A, 0xCEE131F0, 0xC22888A2, 0x54BD4C68, 0x3960B16B, 0xAFF575A1, 0xE2DB4B6D, 0x744E8FA7, 0x199372A4, 0x8F06B66E, 0xD1FDAE25, 0x47686AEF, 0x2AB597EC, 0xBC205326, 0xF10E6DEA, 0x679BA920, 0x0A465423, 0x9CD390E9, 0x901A29BB, 0x068FED71, 0x6B521072, 0xFDC7D4B8, 0xB0E9EA74, 0x267C2EBE, 0x4BA1D3BD, 0xDD341777, 0x5232A119, 0xC4A765D3, 0xA97A98D0, 0x3FEF5C1A, 0x72C162D6, 0xE454A61C, 0x89895B1F, 0x1F1C9FD5, 0x13D52687, 0x8540E24D, 0xE89D1F4E, 0x7E08DB84, 0x3326E548, 0xA5B32182, 0xC86EDC81, 0x5EFB184B, 0x7598EC17, 0xE30D28DD, 0x8ED0D5DE, 0x18451114, 0x556B2FD8, 0xC3FEEB12, 0xAE231611, 0x38B6D2DB, 0x347F6B89, 0xA2EAAF43, 0xCF375240, 0x59A2968A, 0x148CA846, 0x82196C8C, 0xEFC4918F, 0x79515545, 0xF657E32B, 0x60C227E1, 0x0D1FDAE2, 0x9B8A1E28, 0xD6A420E4, 0x4031E42E, 0x2DEC192D, 0xBB79DDE7, 0xB7B064B5, 0x2125A07F, 0x4CF85D7C, 0xDA6D99B6, 0x9743A77A, 0x01D663B0, 0x6C0B9EB3, 0xFA9E5A79, 0xA4654232, 0x32F086F8, 0x5F2D7BFB, 0xC9B8BF31, 0x849681FD, 0x12034537, 0x7FDEB834, 0xE94B7CFE, 0xE582C5AC, 0x73170166, 0x1ECAFC65, 0x885F38AF, 0xC5710663, 0x53E4C2A9, 0x3E393FAA, 0xA8ACFB60, 0x27AA4D0E, 0xB13F89C4, 0xDCE274C7, 0x4A77B00D, 0x07598EC1, 0x91CC4A0B, 0xFC11B708, 0x6A8473C2, 0x664DCA90, 0xF0D80E5A, 0x9D05F359, 0x0B903793, 0x46BE095F, 0xD02BCD95, 0xBDF63096, 0x2B63F45C, 0xEB31D82E, 0x7DA41CE4, 0x1079E1E7, 0x86EC252D, 0xCBC21BE1, 0x5D57DF2B, 0x308A2228, 0xA61FE6E2, 0xAAD65FB0, 0x3C439B7A, 0x519E6679, 0xC70BA2B3, 0x8A259C7F, 0x1CB058B5, 0x716DA5B6, 0xE7F8617C, 0x68FED712, 0xFE6B13D8, 0x93B6EEDB, 0x05232A11, 0x480D14DD, 0xDE98D017, 0xB3452D14, 0x25D0E9DE, 0x2919508C, 0xBF8C9446, 0xD2516945, 0x44C4AD8F, 0x09EA9343, 0x9F7F5789, 0xF2A2AA8A, 0x64376E40, 0x3ACC760B, 0xAC59B2C1, 0xC1844FC2, 0x57118B08, 0x1A3FB5C4, 0x8CAA710E, 0xE1778C0D, 0x77E248C7, 0x7B2BF195, 0xEDBE355F, 0x8063C85C, 0x16F60C96, 0x5BD8325A, 0xCD4DF690, 0xA0900B93, 0x3605CF59, 0xB9037937, 0x2F96BDFD, 0x424B40FE, 0xD4DE8434, 0x99F0BAF8, 0x0F657E32, 0x62B88331, 0xF42D47FB, 0xF8E4FEA9, 0x6E713A63, 0x03ACC760, 0x953903AA, 0xD8173D66, 0x4E82F9AC, 0x235F04AF, 0xB5CAC065, 0x9EA93439, 0x083CF0F3, 0x65E10DF0, 0xF374C93A, 0xBE5AF7F6, 0x28CF333C, 0x4512CE3F, 0xD3870AF5, 0xDF4EB3A7, 0x49DB776D, 0x24068A6E, 0xB2934EA4, 0xFFBD7068, 0x6928B4A2, 0x04F549A1, 0x92608D6B, 0x1D663B05, 0x8BF3FFCF, 0xE62E02CC, 0x70BBC606, 0x3D95F8CA, 0xAB003C00, 0xC6DDC103, 0x504805C9, 0x5C81BC9B, 0xCA147851, 0xA7C98552, 0x315C4198, 0x7C727F54, 0xEAE7BB9E, 0x873A469D, 0x11AF8257, 0x4F549A1C, 0xD9C15ED6, 0xB41CA3D5, 0x2289671F, 0x6FA759D3, 0xF9329D19, 0x94EF601A, 0x027AA4D0, 0x0EB31D82, 0x9826D948, 0xF5FB244B, 0x636EE081, 0x2E40DE4D, 0xB8D51A87, 0xD508E784, 0x439D234E, 0xCC9B9520, 0x5A0E51EA, 0x37D3ACE9, 0xA1466823, 0xEC6856EF, 0x7AFD9225, 0x17206F26, 0x81B5ABEC, 0x8D7C12BE, 0x1BE9D674, 0x76342B77, 0xE0A1EFBD, 0xAD8FD171, 0x3B1A15BB, 0x56C7E8B8, 0xC0522C72
    };

private static final long[] numArr2 = new long[] {
            0L, 1996959894L, 3993919788L, 2567524794L, 124634137L, 1886057615L, 3915621685L, 2657392035L, 249268274L, 2044508324L, 3772115230L, 2547177864L, 162941995L, 2125561021L, 3887607047L, 2428444049L, 498536548L, 1789927666L, 4089016648L, 2227061214L, 450548861L, 1843258603L, 4107580753L, 2211677639L, 325883990L, 1684777152L, 4251122042L, 2321926636L, 335633487L, 1661365465L, 4195302755L, 2366115317L, 997073096L, 1281953886L, 3579855332L, 2724688242L, 1006888145L, 1258607687L, 3524101629L, 2768942443L, 901097722L, 1119000684L, 3686517206L, 2898065728L, 853044451L, 1172266101L, 3705015759L, 2882616665L, 651767980L, 1373503546L, 3369554304L, 3218104598L, 565507253L, 1454621731L, 3485111705L, 3099436303L, 671266974L, 1594198024L, 3322730930L, 2970347812L, 795835527L, 1483230225L, 3244367275L, 3060149565L, 1994146192L, 31158534L, 2563907772L, 4023717930L, 1907459465L, 112637215L, 2680153253L, 3904427059L, 2013776290L, 251722036L, 2517215374L, 3775830040L, 2137656763L, 141376813L, 2439277719L, 3865271297L, 1802195444L, 476864866L, 2238001368L, 4066508878L, 1812370925L, 453092731L, 2181625025L, 4111451223L, 1706088902L, 314042704L, 2344532202L, 4240017532L, 1658658271L, 366619977L, 2362670323L, 4224994405L, 1303535960L, 984961486L, 2747007092L, 3569037538L, 1256170817L, 1037604311L, 2765210733L, 3554079995L, 1131014506L, 879679996L, 2909243462L, 3663771856L, 1141124467L, 855842277L, 2852801631L, 3708648649L, 1342533948L, 654459306L, 3188396048L, 3373015174L, 1466479909L, 544179635L, 3110523913L, 3462522015L, 1591671054L, 702138776L, 2966460450L, 3352799412L, 1504918807L, 783551873L, 3082640443L, 3233442989L, 3988292384L, 2596254646L, 62317068L, 1957810842L, 3939845945L, 2647816111L, 81470997L, 1943803523L, 3814918930L, 2489596804L, 225274430L, 2053790376L, 3826175755L, 2466906013L, 167816743L, 2097651377L, 4027552580L, 2265490386L, 503444072L, 1762050814L, 4150417245L, 2154129355L, 426522225L, 1852507879L, 4275313526L, 2312317920L, 282753626L, 1742555852L, 4189708143L, 2394877945L, 397917763L, 1622183637L, 3604390888L, 2714866558L, 953729732L, 1340076626L, 3518719985L, 2797360999L, 1068828381L, 1219638859L, 3624741850L, 2936675148L, 906185462L, 1090812512L, 3747672003L, 2825379669L, 829329135L, 1181335161L, 3412177804L, 3160834842L, 628085408L, 1382605366L, 3423369109L, 3138078467L, 570562233L, 1426400815L, 3317316542L, 2998733608L, 733239954L, 1555261956L, 3268935591L, 3050360625L, 752459403L, 1541320221L, 2607071920L, 3965973030L, 1969922972L, 40735498L, 2617837225L, 3943577151L, 1913087877L, 83908371L, 2512341634L, 3803740692L, 2075208622L, 213261112L, 2463272603L, 3855990285L, 2094854071L, 198958881L, 2262029012L, 4057260610L, 1759359992L, 534414190L, 2176718541L, 4139329115L, 1873836001L, 414664567L, 2282248934L, 4279200368L, 1711684554L, 285281116L, 2405801727L, 4167216745L, 1634467795L, 376229701L, 2685067896L, 3608007406L, 1308918612L, 956543938L, 2808555105L, 3495958263L, 1231636301L, 1047427035L, 2932959818L, 3654703836L, 1088359270L, 936918000L, 2847714899L, 3736837829L, 1202900863L, 817233897L, 3183342108L, 3401237130L, 1404277552L, 615818150L, 3134207493L, 3453421203L, 1423857449L, 601450431L, 3009837614L, 3294710456L, 1567103746L, 711928724L, 3020668471L, 3272380065L, 1510334235L, 755167117L
    };

Test with CRC32 from java.util.zip:

public static String crc32(byte[] data) {
    Checksum c = new CRC32();

    c.update(1);
    c.update(data);

    return String.valueOf(Long.parseLong(Long.toHexString(c.getValue()), 16));    // 1544046132
}

The solution from [3]

public static String crc32(byte[] data){
    int crc = Integer.MAX_VALUE;

    for (byte b : data)
        crc = numArr[(crc & 0xff) ^ (b & 0xff) & 255] ^ (crc >>> 8);

    crc = ~crc; // flip bit/sign

    return String.valueOf(Long.parseLong(Integer.toHexString(crc), 16));    // 1120211745
}

This implementation uses Guava and was directly transformed from me. I also try BigInteger, bit operations to enforce unsigned and use byte arrays instead of int or long.

public static String crc32(byte[] data) {
    long num = UnsignedInteger.MAX_VALUE.longValue();

    for (byte aByte : data)
        num = numArr2[(Integer.parseUnsignedInt(Long.toUnsignedString(num)) ^ aByte) & 255] ^ (num >>> 8);

    num ^= UnsignedInteger.MAX_VALUE.longValue();

    return String.valueOf(num);     // 2128031166
}

Update 3

I tried a new start with BigInteger and now the result is closer. The CRC is 1190225612 (expected: 1195433981).

public static String crc32(byte[] bytes) {
    BigInteger num = BigInteger.valueOf(0xffffffffL);

    for (byte aByte: bytes)
        num = BigInteger.valueOf(numArr[num.xor(BigInteger.valueOf(aByte)).and(BigInteger.valueOf(numArr.length - 1)).intValue()]).xor((num.shiftRight(8)));

    num = num.xor(BigInteger.valueOf(0xffffffffL));

    System.out.println("1195433981");
    return String.valueOf(~num.intValue());
}

Update 4

Update the procedure description. Not the whole line with the Stamp tag will be removed instead of only the value from the CRC attribute will be removed.

2
javaunsignedcrc32
I tried to use the algorithm from stackoverflow.com/questions/14187955/… with the given table and the int array from the decompiled class but the problem is still there. – BlackRose01
What exactly is "the problem"? What CRC are you getting, as compared to what you are expecting? – Mark Adler
So where is your attempt at implementing the CRC in Java? That needs to be in the question. – Mark Adler
Sorry, I add the missing information as Update 1 and Update 2. – BlackRose01

2 Answers

1
votes

You have the initial CRC wrong. It is 1. From the document you linked:

The seed value shall be "1" (see previousCrc32 = 1 in Figure B.1 and Figure B.2).

That value is then inverted before the loop, so at that point your "num" should be 0xfffffffe.

You numArr1 is correct. I don't know where your numArr2 came from.

All you need is this, calling with the first argument being 1:

static private int crc32iodd(int crc, byte[] data){
    crc = ~crc;
    for (byte b : data)
        crc = numArr1[(crc ^ b) & 0xff] ^ (crc >>> 8);
    return ~crc;
}

Since Java doesn't have unsigned int, half the time your result will be negative. That's fine, since it's the exact same 32 bits as you would have as an unsigned result, just printed differently.

There is no sense of "closer" for the answer. The integer difference between what you want and what you're getting has no meaning in the world of CRCs, since they are not integer calculations.

Update:

Looking more closely at your links and the CRC reference code you put in your question, it appears you have referenced entirely the wrong documents for the CRC you actually need. You referenced the CRC for BLOBs used for firmware updates, which is not the CRC used for validation of the XML files. This document provides the specification for the CRC used for the XML files as the 32-bit CRC found in the ITU-T recommendation V.42. That is a different CRC using a different polynomial and different initial value. It is in fact the standard CRC-32 used by zip, and is available in Java as java.util.zip.CRC32. You don't need to write any CRC code. Just use that.

That document also notes but does not detail special processing of the XML input before computing the CRC. You will need to do more research to find out exactly what the CRC is calculated over in the XML file, and how it is pre-processed. This package has a description that notes that the associated language xml's have the CRC of main xml's appended to the end before each of their CRC calculations. However it is not made clear as to exactly how the CRC is appended.

This time please conduct adequate research and verification on your part, before coming here with questions about how to implement an incorrectly identified CRC.

1
votes

For the sake of completeness.

You are right. I can use the java.util.zip.CRC32. I think the problem was that I try at the beginning of my implementation tests to use the whole xml file and so I thought that the description in the PDF was wrong.

And here is the solution: If you have a IODD XML file than you have to remove the value of crc in the stamp-tag. Subsequently, if not already done, convert the file content without the crc-value to a byte array. And now you can use one of these two functions:

Implementation with java.util.zip.CRC32

public boolean isValid() {
    CRC32 m = new CRC32();
    m.update(file);
    long x = 1195433981L;
    
    return (m.getValue() == x);
}

Manual implementation (The table is according to the site https://rosettacode.org/wiki/CRC-32#Lingo or https://web.mit.edu/freebsd/head/sys/libkern/crc32.c)

public class Crc32 {
    private static final long[] numArr2 = new long[] {
            0L, 1996959894L, 3993919788L, 2567524794L, 124634137L, 1886057615L, 3915621685L, 2657392035L, 249268274L, 2044508324L, 3772115230L, 2547177864L, 162941995L, 2125561021L, 3887607047L, 2428444049L, 498536548L, 1789927666L, 4089016648L, 2227061214L, 450548861L, 1843258603L, 4107580753L, 2211677639L, 325883990L, 1684777152L, 4251122042L, 2321926636L, 335633487L, 1661365465L, 4195302755L, 2366115317L, 997073096L, 1281953886L, 3579855332L, 2724688242L, 1006888145L, 1258607687L, 3524101629L, 2768942443L, 901097722L, 1119000684L, 3686517206L, 2898065728L, 853044451L, 1172266101L, 3705015759L, 2882616665L, 651767980L, 1373503546L, 3369554304L, 3218104598L, 565507253L, 1454621731L, 3485111705L, 3099436303L, 671266974L, 1594198024L, 3322730930L, 2970347812L, 795835527L, 1483230225L, 3244367275L, 3060149565L, 1994146192L, 31158534L, 2563907772L, 4023717930L, 1907459465L, 112637215L, 2680153253L, 3904427059L, 2013776290L, 251722036L, 2517215374L, 3775830040L, 2137656763L, 141376813L, 2439277719L, 3865271297L, 1802195444L, 476864866L, 2238001368L, 4066508878L, 1812370925L, 453092731L, 2181625025L, 4111451223L, 1706088902L, 314042704L, 2344532202L, 4240017532L, 1658658271L, 366619977L, 2362670323L, 4224994405L, 1303535960L, 984961486L, 2747007092L, 3569037538L, 1256170817L, 1037604311L, 2765210733L, 3554079995L, 1131014506L, 879679996L, 2909243462L, 3663771856L, 1141124467L, 855842277L, 2852801631L, 3708648649L, 1342533948L, 654459306L, 3188396048L, 3373015174L, 1466479909L, 544179635L, 3110523913L, 3462522015L, 1591671054L, 702138776L, 2966460450L, 3352799412L, 1504918807L, 783551873L, 3082640443L, 3233442989L, 3988292384L, 2596254646L, 62317068L, 1957810842L, 3939845945L, 2647816111L, 81470997L, 1943803523L, 3814918930L, 2489596804L, 225274430L, 2053790376L, 3826175755L, 2466906013L, 167816743L, 2097651377L, 4027552580L, 2265490386L, 503444072L, 1762050814L, 4150417245L, 2154129355L, 426522225L, 1852507879L, 4275313526L, 2312317920L, 282753626L, 1742555852L, 4189708143L, 2394877945L, 397917763L, 1622183637L, 3604390888L, 2714866558L, 953729732L, 1340076626L, 3518719985L, 2797360999L, 1068828381L, 1219638859L, 3624741850L, 2936675148L, 906185462L, 1090812512L, 3747672003L, 2825379669L, 829329135L, 1181335161L, 3412177804L, 3160834842L, 628085408L, 1382605366L, 3423369109L, 3138078467L, 570562233L, 1426400815L, 3317316542L, 2998733608L, 733239954L, 1555261956L, 3268935591L, 3050360625L, 752459403L, 1541320221L, 2607071920L, 3965973030L, 1969922972L, 40735498L, 2617837225L, 3943577151L, 1913087877L, 83908371L, 2512341634L, 3803740692L, 2075208622L, 213261112L, 2463272603L, 3855990285L, 2094854071L, 198958881L, 2262029012L, 4057260610L, 1759359992L, 534414190L, 2176718541L, 4139329115L, 1873836001L, 414664567L, 2282248934L, 4279200368L, 1711684554L, 285281116L, 2405801727L, 4167216745L, 1634467795L, 376229701L, 2685067896L, 3608007406L, 1308918612L, 956543938L, 2808555105L, 3495958263L, 1231636301L, 1047427035L, 2932959818L, 3654703836L, 1088359270L, 936918000L, 2847714899L, 3736837829L, 1202900863L, 817233897L, 3183342108L, 3401237130L, 1404277552L, 615818150L, 3134207493L, 3453421203L, 1423857449L, 601450431L, 3009837614L, 3294710456L, 1567103746L, 711928724L, 3020668471L, 3272380065L, 1510334235L, 755167117L
    };

    private static long crc32(byte[] data){
        long crc = 0xFFFFFFFFL;

        for (byte b : data)
            crc = numArr2[(int)(crc ^ b) & 0xff] ^ (crc >>> 8);

        return crc ^ 0xFFFFFFFFL;
    }
    
    public static boolean isValid(byte[] data, long checkCrc) {
        long crc = crc32(data);
        
        return (checkCrc == crc);
    }
}