javacsvfiledelphicrc

Conversion to Java of a Delphi algorithm for CRC checksum for file


I was given this Delphi code:

unit lib_CRC;
interface uses SysUtils;
function CalculateCRC(Text: String): String;
implementation{ CRC Code generation routines }

const{: @summary CRC Code generation array }
CRCTable : array [0..255] of Cardinal = 
(
    $00000000, $77073096, $ee0e612c, $990951ba,
    $076dc419, $706af48f, $e963a535, $9e6495a3,
    $0edb8832, $79dcb8a4, $e0d5e91e, $97d2d988,
    $09b64c2b, $7eb17cbd, $e7b82d07, $90bf1d91,

    $1db71064, $6ab020f2, $f3b97148, $84be41de,
    $1adad47d, $6ddde4eb, $f4d4b551, $83d385c7,
    $136c9856, $646ba8c0, $fd62f97a, $8a65c9ec,
    $14015c4f, $63066cd9, $fa0f3d63, $8d080df5,

    $3b6e20c8, $4c69105e, $d56041e4, $a2677172,
    $3c03e4d1, $4b04d447, $d20d85fd, $a50ab56b,
    $35b5a8fa, $42b2986c, $dbbbc9d6, $acbcf940,
    $32d86ce3, $45df5c75, $dcd60dcf, $abd13d59,

    $26d930ac, $51de003a, $c8d75180, $bfd06116,
    $21b4f4b5, $56b3c423, $cfba9599, $b8bda50f,
    $2802b89e, $5f058808, $c60cd9b2, $b10be924,
    $2f6f7c87, $58684c11, $c1611dab, $b6662d3d,

    $76dc4190,  $01db7106, $98d220bc,   $efd5102a,
    $71b18589, $06b6b51f, $9fbfe4a5, $e8b8d433,
    $7807c9a2, $0f00f934, $9609a88e, $e10e9818,
    $7f6a0dbb, $086d3d2d, $91646c97, $e6635c01,

    $6b6b51f4, $1c6c6162, $856530d8, $f262004e,
    $6c0695ed, $1b01a57b, $8208f4c1, $f50fc457,
    $65b0d9c6, $12b7e950, $8bbeb8ea, $fcb9887c,
    $62dd1ddf, $15da2d49, $8cd37cf3, $fbd44c65,

    $4db26158, $3ab551ce, $a3bc0074, $d4bb30e2,
    $4adfa541, $3dd895d7, $a4d1c46d, $d3d6f4fb, 
    $4369e96a, $346ed9fc, $ad678846, $da60b8d0,
    $44042d73, $33031de5, $aa0a4c5f, $dd0d7cc9,

    $5005713c, $270241aa, $be0b1010, $c90c2086,
    $5768b525, $206f85b3, $b966d409, $ce61e49f,
    $5edef90e, $29d9c998, $b0d09822, $c7d7a8b4,
    $59b33d17, $2eb40d81, $b7bd5c3b, $c0ba6cad,

    $edb88320, $9abfb3b6, $03b6e20c, $74b1d29a,
    $ead54739, $9dd277af, $04db2615, $73dc1683,
    $e3630b12, $94643b84, $0d6d6a3e, $7a6a5aa8,
    $e40ecf0b, $9309ff9d, $0a00ae27, $7d079eb1,

    $f00f9344, $8708a3d2, $1e01f268, $6906c2fe,
    $f762575d, $806567cb,   $196c3671, $6e6b06e7,
    $fed41b76, $89d32be0, $10da7a5a, $67dd4acc,
    $f9b9df6f, $8ebeeff9, $17b7be43, $60b08ed5,

    $d6d6a3e8, $a1d1937e, $38d8c2c4, $4fdff252,
    $d1bb67f1, $a6bc5767, $3fb506dd, $48b2364b,
    $d80d2bda, $af0a1b4c, $36034af6, $41047a60,
    $df60efc3,  $a867df55, $316e8eef, $4669be79,

    $cb61b38c, $bc66831a, $256fd2a0, $5268e236,
    $cc0c7795, $bb0b4703, $220216b9, $5505262f,
    $c5ba3bbe, $b2bd0b28, $2bb45a92, $5cb36a04,
    $c2d7ffa7, $b5d0cf31, $2cd99e8b, $5bdeae1d,

    $9b64c2b0, $ec63f226, $756aa39c, $026d930a,
    $9c0906a9, $eb0e363f, $72076785, $05005713,
    $95bf4a82, $e2b87a14, $7bb12bae, $0cb61b38,
    $92d28e9b, $e5d5be0d, $7cdcefb7, $0bdbdf21,

    $86d3d2d4, $f1d4e242, $68ddb3f8, $1fda836e,
    $81be16cd, $f6b9265b, $6fb077e1, $18b74777,
    $88085ae6, $ff0f6a70, $66063bca, $11010b5c,
    $8f659eff, $f862ae69, $616bffd3, $166ccf45,

    $a00ae278, $d70dd2ee, $4e048354, $3903b3c2,
    $a7672661, $d06016f7, $4969474d, $3e6e77db,
    $aed16a4a, $d9d65adc, $40df0b66, $37d83bf0,
    $a9bcae53, $debb9ec5, $47b2cf7f, $30b5ffe9,

    $bdbdf21c, $cabac28a, $53b39330, $24b4a3a6,
    $bad03605, $cdd70693, $54de5729, $23d967bf,
    $b3667a2e, $c4614ab8, $5d681b02, $2a6f2b94,
    $b40bbe37, $c30c8ea1, $5a05df1b, $2d02ef8d
);


{: @summary CRC Codegeneration routine }
function CalculateCRC(Text: String): String ;
var Index  : Integer;
    CRCVal : Cardinal;

begin
    CRCVal:=0;
    for Index:=1 to Length(Text)
    do CRCVal:=CRCTable[Byte(CRCVal xor Ord(Text[Index]))] xor((CRCVal shr 8) and $00FFFFFF);
    Result:=UpperCase(IntToHex(CRCVal, 8));
end;
end.

For which I have produced my correspondent Java code:

package com.noemalife.hal.communication.test.drivers;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;

public class LyrasCRC {

    private static final int[] CRC_TABLE = {
                        0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
                        0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
                        0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
                        0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
                        
                        0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
                        0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
                        0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
                        0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
                        
                        0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
                        0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
                        0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
                        0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
                        
                        0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
                        0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
                        0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
                        0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
                        
                        0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
                        0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
                        0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
                        0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
                        
                        0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
                        0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
                        0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
                        0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
                        
                        0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
                        0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 
                        0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
                        0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
                        
                        0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
                        0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
                        0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
                        0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
                        
                        0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
                        0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
                        0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
                        0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
                        
                        0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
                        0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
                        0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
                        0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
                        
                        0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
                        0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
                        0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
                        0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
                        
                        0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
                        0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
                        0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
                        0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
                        
                        0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
                        0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
                        0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
                        0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
                        
                        0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
                        0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
                        0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
                        0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
                        
                        0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
                        0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
                        0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
                        0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
                        
                        0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
                        0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
                        0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
                        0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d};

    public static void main(String [] args) throws IOException {
        byte[] bytes = Files.readAllBytes(new File("C:\\...").toPath());
        System.out.println(calculateLyrasCRC(bytes));
    }
        
    public static String calculateLyrasCRC(byte[] text) {
        int crcValue = 0;
        for(int i = 0; i<text.length; i++) {
            crcValue = CRC_TABLE[(crcValue ^ text[i])] ^ ((crcValue >> 8) & 0x00FFFFFF);
        }
        String crcValueStr = Integer.toHexString(crcValue).toUpperCase();
        return crcValueStr;
    }
}

The ouput of that CRC calculation must be appended at the end of the file before being sent. Anyway, the procedure fails: after one or two iterations it seems to generate a big negative number used to access the CRC_TABLE for which I get a java.lang.ArrayIndexOutOfBoundsException.

I have seen these examples: Example in C Example in C#

but I cannot get the difference, except in the use of the final XOR. Do you have any ideas where I am making the mistake?

POSSIBLE SOLUTION As suggested by @g00se and @Matthias B a working solution may be

crcValue = CRC_TABLE[(crcValue ^ text[i]) & 0xFF] ^ ((crcValue >> 8) & 0x00FFFFFF);

I've said "may be" because actually I have no possibility nor feedback to verify if the calculated value is logically correct


Solution

  • The Java code is missing the type cast to Byte that the Delphi code has.

    The type cast to Byte truncates the value so that it always stays in the 0-255 range, which fits what the array needs to be indexed by.

    Note that in Delphi, Byte is an unsigned 8-bit number, while Java's byte data type is signed, so you cannot use Java's byte directly. I believe that the way to truncate an integer to an unsigned byte in Java is by taking (value & 0xFF).