Same code for CRC32 in JScript and VB.Net produce different result

[Bicurico]

Hello,

Please don't ask why: I need to calculate CRC32 in JScript (embedded in another application, so no access to Crypto stuff) and in VB.Net.

I have this source code for JScript, which at least doesn't produce an error:

Code: [Select]

function CRC32(str){
var CRCTable=[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];
var len=str.length;
var r=0xffffffff;
for(var i=0;i<len;i++){
r=(r>>8)^CRCTable[str[i]^(r&0x000000FF)];
}
return~r;
}

I used ChatGPT to help me convert this code into VB.Net and ended up with this:

Code: [Select]

    Function CRC32(text As String) As UInt64
        Dim CRCTable As UInt32() = {&H0UI, &H77073096UI, &HEE0E612CUI, &H990951BAUI, &H76DC419UI, &H706AF48FUI, &HE963A535UI, &H9E6495A3UI, &HEDB8832UI, &H79DCB8A4UI, &HE0D5E91EUI, &H97D2D988UI, &H9B64C2BUI, &H7EB17CBDUI, &HE7B82D07UI, &H90BF1D91UI, &H1DB71064UI, &H6AB020F2UI, &HF3B97148UI, &H84BE41DEUI, &H1ADAD47DUI, &H6DDDE4EBUI, &HF4D4B551UI, &H83D385C7UI, &H136C9856UI, &H646BA8C0UI, &HFD62F97AUI, &H8A65C9ECUI, &H14015C4FUI, &H63066CD9UI, &HFA0F3D63UI, &H8D080DF5UI, &H3B6E20C8UI, &H4C69105EUI, &HD56041E4UI, &HA2677172UI, &H3C03E4D1UI, &H4B04D447UI, &HD20D85FDUI, &HA50AB56BUI, &H35B5A8FAUI, &H42B2986CUI, &HDBBBC9D6UI, &HACBCF940UI, &H32D86CE3UI, &H45DF5C75UI, &HDCD60DCFUI, &HABD13D59UI, &H26D930ACUI, &H51DE003AUI, &HC8D75180UI, &HBFD06116UI, &H21B4F4B5UI, &H56B3C423UI, &HCFBA9599UI, &HB8BDA50FUI, &H2802B89EUI, &H5F058808UI, &HC60CD9B2UI, &HB10BE924UI, &H2F6F7C87UI, &H58684C11UI, &HC1611DABUI, &HB6662D3DUI, &H76DC4190UI, &H1DB7106UI, &H98D220BCUI, &HEFD5102AUI, &H71B18589UI, &H6B6B51FUI, &H9FBFE4A5UI, &HE8B8D433UI, &H7807C9A2UI, &HF00F934UI, &H9609A88EUI, &HE10E9818UI, &H7F6A0DBBUI, &H86D3D2DUI, &H91646C97UI, &HE6635C01UI, &H6B6B51F4UI, &H1C6C6162UI, &H856530D8UI, &HF262004EUI, &H6C0695EDUI, &H1B01A57BUI, &H8208F4C1UI, &HF50FC457UI, &H65B0D9C6UI, &H12B7E950UI, &H8BBEB8EAUI, &HFCB9887CUI, &H62DD1DDFUI, &H15DA2D49UI, &H8CD37CF3UI, &HFBD44C65UI, &H4DB26158UI, &H3AB551CEUI, &HA3BC0074UI, &HD4BB30E2UI, &H4ADFA541UI, &H3DD895D7UI, &HA4D1C46DUI, &HD3D6F4FBUI, &H4369E96AUI, &H346ED9FCUI, &HAD678846UI, &HDA60B8D0UI, &H44042D73UI, &H33031DE5UI, &HAA0A4C5FUI, &HDD0D7CC9UI, &H5005713CUI, &H270241AAUI, &HBE0B1010UI, &HC90C2086UI, &H5768B525UI, &H206F85B3UI, &HB966D409UI, &HCE61E49FUI, &H5EDEF90EUI, &H29D9C998UI, &HB0D09822UI, &HC7D7A8B4UI, &H59B33D17UI, &H2EB40D81UI, &HB7BD5C3BUI, &HC0BA6CADUI, &HEDB88320UI, &H9ABFB3B6UI, &H3B6E20CUI, &H74B1D29AUI, &HEAD54739UI, &H9DD277AFUI, &H4DB2615UI, &H73DC1683UI, &HE3630B12UI, &H94643B84UI, &HD6D6A3EUI, &H7A6A5AA8UI, &HE40ECF0BUI, &H9309FF9DUI, &HA00AE27UI, &H7D079EB1UI, &HF00F9344UI, &H8708A3D2UI, &H1E01F268UI, &H6906C2FEUI, &HF762575DUI, &H806567CBUI, &H196C3671UI, &H6E6B06E7UI, &HFED41B76UI, &H89D32BE0UI, &H10DA7A5AUI, &H67DD4ACCUI, &HF9B9DF6FUI, &H8EBEEFF9UI, &H17B7BE43UI, &H60B08ED5UI, &HD6D6A3E8UI, &HA1D1937EUI, &H38D8C2C4UI, &H4FDFF252UI, &HD1BB67F1UI, &HA6BC5767UI, &H3FB506DDUI, &H48B2364BUI, &HD80D2BDAUI, &HAF0A1B4CUI, &H36034AF6UI, &H41047A60UI, &HDF60EFC3UI, &HA867DF55UI, &H316E8EEFUI, &H4669BE79UI, &HCB61B38CUI, &HBC66831AUI, &H256FD2A0UI, &H5268E236UI, &HCC0C7795UI, &HBB0B4703UI, &H220216B9UI, &H5505262FUI, &HC5BA3BBEUI, &HB2BD0B28UI, &H2BB45A92UI, &H5CB36A04UI, &HC2D7FFA7UI, &HB5D0CF31UI, &H2CD99E8BUI, &H5BDEAE1DUI, &H9B64C2B0UI, &HEC63F226UI, &H756AA39CUI, &H26D930AUI, &H9C0906A9UI, &HEB0E363FUI, &H72076785UI, &H5005713UI, &H95BF4A82UI, &HE2B87A14UI, &H7BB12BAEUI, &HCB61B38UI, &H92D28E9BUI, &HE5D5BE0DUI, &H7CDCEFB7UI, &HBDBDF21CUI, &HCABAC28AUI, &H53B39330UI, &H24B4A3A6UI, &HBAD03605UI, &HCDD70693UI, &H54DE5729UI, &H23D967BFUI, &HB3667A2EUI, &HC4614AB8UI, &H5D681B02UI, &H2A6F2B94UI, &HB40BBE37UI, &HC30C8EA1UI, &H5A05DF1BUI, &H2D02EF8D}
        Dim len As Integer = text.Length
        Dim r As UInt32 = &HFFFFFFFFUI
        For i As Integer = 0 To len - 1
            r = (r >> 8) Xor CRCTable(Convert.ToByte(text(i)) Xor (r And &HFF))
        Next
        Return Not r
    End Function

If I call the JScript function with argument "AAAAA" I get 337647727 as the result for the CRC32.

But calling the VB.Net function with argument "AAAAA" produces 435704073 as the result for the CRC32.

Has anyone an idea why this is happening?

I don't need this source code to be compatible with any other CRC32 algorithm - I just need the JScript and VB.Net versions to output the same result for any given equal string.

The string can be simple ASCII (just numbers and letters).

Thanks,
Vitor

[Bicurico]

Also, the JScript function produces negative CRC32 numbers for some strings, while the VB.Net version will complain with out of range error.

[magic]

Dunno, I would probably make it print the current values of internal variables on every iteration to see where things go unexpected.

The long expression could be split into parts and each part printed separately.

[ataradov]

The tables are completely different. That's ChatGPT programming for you, the way of the future.

[jm_araujo]

I get the same results with:

Code: [Select]

function CRC32(str){
var CRCTable=[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];
var len=str.length;
var r=0xffffffff;
for(var i=0;i<len;i++){
r=((r>>8)^CRCTable[str[i].charCodeAt()^(r&0x000000FF)]);
}
return(~r>>>0);;
}
In my debugging found out you need the "charCodeAt()" to convert from string to int.
The return with ">>>0" was a trick found online to return unsigned numbers in js

Edit: the VB.Net table is incomplete.

[Bicurico]

@ataradov: The tables are the same, I just added the correct formatting for the VB variant.

@jm_araujo: I tested charCodeAt() but had to modify your code, because as it is, the interpreter would give an error.

This code:

Code: [Select]

function CRC32(str){
var CRCTable=[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];
var len=str.length;
var r=0xffffffff;
for(var i=0;i<len;i++){
r=((r>>8)^CRCTable[str.charCodeAt(i)^(r&0x000000FF)]);
}
return(~r>>>0);;
}

No produces "888815995" for string "AAAAA".

So definitely something changed and it probably is the stupid string handling...

Thanks for the help, I will keep trying to figue this one out.

[ataradov]

They are not even of the same size. The VB one has 223 entries. And the table must have 256 entries.

[KE5FX]

GPT assistants are like Stack Overflow.  They can give you a good starting point but you will have to do some work to integrate and debug the results.  No big surprise there.

AI, however, will get better, while it's safe to say that Stack Overflow won't.

[Bicurico]

They are not even of the same size. The VB one has 223 entries. And the table must have 256 entries.

Hi,

I copied the table manually from the JScript to VB.Net and used Notepad++ to edit the different formatting.
Just double checked and I get 256 UINT values.

Thanks,
Vitor

[ataradov]

Ok, then it is not the same table as included in the first post. Because that one only has 223 entries and the later part of the table is missing a lot of them.

[Bicurico]

Yes, sorry about that.
Initially I used the table from ChatGPT, but then replaced it to make sure tables were the same.

I suspect this is due to ASCII conversion in byte or integer.

The thing is that I don't know JScript and most examples revert to JavaScript for HTML. My use case is automation inside an application that supports Microsoft JScript.

[Bicurico]

I fixed it!

The problem was that JScript always uses INT32, while I was using UINT32 in VB.Net.

The difference is that INT32 is signed, while UINT32 is not - the difference beeing the last bit (most left one). This produced differences in the bit shift.

The two functions produce the same output:

JSCRIPT

Code: [Select]

function CRC32(str){
var CRCTable=[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];
var len=str.length;
var r=0xffffffff;
for(var i=0;i<len;i++){
r=(r>>8)^CRCTable[str.charCodeAt(i)^(r&0x000000FF)];
}
return (~r>>>0);;
}

VB.Net

Code: [Select]

    Function CRC32(text As String) As Int64
        Dim CRCTable As Int32() = {&H0, &H77073096, &HEE0E612C, &H990951BA, &H76DC419, &H706AF48F, &HE963A535, &H9E6495A3, &HEDB8832, &H79DCB8A4, &HE0D5E91E, &H97D2D988, &H9B64C2B, &H7EB17CBD, &HE7B82D07, &H90BF1D91, &H1DB71064, &H6AB020F2, &HF3B97148, &H84BE41DE, &H1ADAD47D, &H6DDDE4EB, &HF4D4B551, &H83D385C7, &H136C9856, &H646BA8C0, &HFD62F97A, &H8A65C9EC, &H14015C4F, &H63066CD9, &HFA0F3D63, &H8D080DF5, &H3B6E20C8, &H4C69105E, &HD56041E4, &HA2677172, &H3C03E4D1, &H4B04D447, &HD20D85FD, &HA50AB56B, &H35B5A8FA, &H42B2986C, &HDBBBC9D6, &HACBCF940, &H32D86CE3, &H45DF5C75, &HDCD60DCF, &HABD13D59, &H26D930AC, &H51DE003A, &HC8D75180, &HBFD06116, &H21B4F4B5, &H56B3C423, &HCFBA9599, &HB8BDA50F, &H2802B89E, &H5F058808, &HC60CD9B2, &HB10BE924, &H2F6F7C87, &H58684C11, &HC1611DAB, &HB6662D3D, &H76DC4190, &H1DB7106, &H98D220BC, &HEFD5102A, &H71B18589, &H6B6B51F, &H9FBFE4A5, &HE8B8D433, &H7807C9A2, &HF00F934, &H9609A88E, &HE10E9818, &H7F6A0DBB, &H86D3D2D, &H91646C97, &HE6635C01, &H6B6B51F4, &H1C6C6162, &H856530D8, &HF262004E, &H6C0695ED, &H1B01A57B, &H8208F4C1, &HF50FC457, &H65B0D9C6, &H12B7E950, &H8BBEB8EA, &HFCB9887C, &H62DD1DDF, &H15DA2D49, &H8CD37CF3, &HFBD44C65, &H4DB26158, &H3AB551CE, &HA3BC0074, &HD4BB30E2, &H4ADFA541, &H3DD895D7, &HA4D1C46D, &HD3D6F4FB, &H4369E96A, &H346ED9FC, &HAD678846, &HDA60B8D0, &H44042D73, &H33031DE5, &HAA0A4C5F, &HDD0D7CC9, &H5005713C, &H270241AA, &HBE0B1010, &HC90C2086, &H5768B525, &H206F85B3, &HB966D409, &HCE61E49F, &H5EDEF90E, &H29D9C998, &HB0D09822, &HC7D7A8B4, &H59B33D17, &H2EB40D81, &HB7BD5C3B, &HC0BA6CAD, &HEDB88320, &H9ABFB3B6, &H3B6E20C, &H74B1D29A, &HEAD54739, &H9DD277AF, &H4DB2615, &H73DC1683, &HE3630B12, &H94643B84, &HD6D6A3E, &H7A6A5AA8, &HE40ECF0B, &H9309FF9D, &HA00AE27, &H7D079EB1, &HF00F9344, &H8708A3D2, &H1E01F268, &H6906C2FE, &HF762575D, &H806567CB, &H196C3671, &H6E6B06E7, &HFED41B76, &H89D32BE0, &H10DA7A5A, &H67DD4ACC, &HF9B9DF6F, &H8EBEEFF9, &H17B7BE43, &H60B08ED5, &HD6D6A3E8, &HA1D1937E, &H38D8C2C4, &H4FDFF252, &HD1BB67F1, &HA6BC5767, &H3FB506DD, &H48B2364B, &HD80D2BDA, &HAF0A1B4C, &H36034AF6, &H41047A60, &HDF60EFC3, &HA867DF55, &H316E8EEF, &H4669BE79, &HCB61B38C, &HBC66831A, &H256FD2A0, &H5268E236, &HCC0C7795, &HBB0B4703, &H220216B9, &H5505262F, &HC5BA3BBE, &HB2BD0B28, &H2BB45A92, &H5CB36A04, &HC2D7FFA7, &HB5D0CF31, &H2CD99E8B, &H5BDEAE1D, &H9B64C2B0, &HEC63F226, &H756AA39C, &H26D930A, &H9C0906A9, &HEB0E363F, &H72076785, &H5005713, &H95BF4A82, &HE2B87A14, &H7BB12BAE, &HCB61B38, &H92D28E9B, &HE5D5BE0D, &H7CDCEFB7, &HBDBDF21, &H86D3D2D4, &HF1D4E242, &H68DDB3F8, &H1FDA836E, &H81BE16CD, &HF6B9265B, &H6FB077E1, &H18B74777, &H88085AE6, &HFF0F6A70, &H66063BCA, &H11010B5C, &H8F659EFF, &HF862AE69, &H616BFFD3, &H166CCF45, &HA00AE278, &HD70DD2EE, &H4E048354, &H3903B3C2, &HA7672661, &HD06016F7, &H4969474D, &H3E6E77DB, &HAED16A4A, &HD9D65ADC, &H40DF0B66, &H37D83BF0, &HA9BCAE53, &HDEBB9EC5, &H47B2CF7F, &H30B5FFE9, &HBDBDF21C, &HCABAC28A, &H53B39330, &H24B4A3A6, &HBAD03605, &HCDD70693, &H54DE5729, &H23D967BF, &HB3667A2E, &HC4614AB8, &H5D681B02, &H2A6F2B94, &HB40BBE37, &HC30C8EA1, &H5A05DF1B, &H2D02EF8D}
        Dim len As Integer = text.Length
        Dim r As Int32 = &HFFFFFFFF
        For i As Integer = 0 To len - 1
            r = (r >> 8) Xor CRCTable(Asc(text(i)) Xor (r And &HFF))
            Debug.Print(r)
        Next
        Return Not r And &HFFFFFFFFUI
    End Function

Thanks to all. Sometimes it is good to be able o talk to someone, in order to see stupid mistakes.

[magic]

JavaScript actually treats numbers as double precision IEEE754 floats and apparently converts them to integers somehow for logical operations, but I don't know the details how it's done. Particularly, what's the bit width and what happens when the number is fractional...

In VB I would expect >> to be logical shift for Uint32 and arithmetic shift for Int32, like in most C implementations. The difference is that logical shift zeros the "emptied" leftmost bits, while arithmetic shift sets them to one if the leftmost bit was previously one (this causes negative numbers to stay negative after shifting).

In JS >> apparently means arithmetic shift, and there is supposedly >>> for logical shift, but hell knows how it works exactly.

edit
Actually, hell knows how this works too. Why is it making any difference if all your numbers appear to be positive? Maybe the type of converted numbers in JS is indeed exactly 32 bit signed.

[SiliconWizard]

I used ChatGPT to help me convert this code into VB.Net and ended up with this:
(...)
Has anyone an idea why this is happening?

 

[Bicurico]

You go on laughing.

ChapGPT was a huge help, since I never had programmed in JScript before and I was totally unfamiliar with the operators.

ChatGPT produced a good working code, translating Jscript into VB.Net. Total time was less than three minutes.

It did stumble on the Int32 Vs Uint32 issue, but even here nobody spotted the reason.

And I used it obviously for the original JScript code, too.

I would recommend ChatGPT as a programming aid any day. Did I mention I am using the free version?

[golden_labels]

Laughing without explaining is not constructive. Even worse, if the laughing person is not right.

Earlier I avoided responding, but I now my 3 cents may be worth something. I see two problems here. One related to ChatGPT, one not.

CRC may use many different polynomials. There are at least a few of degree 32 in use and the actual implementations also differ in how the state is initialized and post-processed. I do not expect a programmer to profoundly understand maths behind CRC, but being conscious of the polynomial in use is critical. You are most likely to encounter IEEE 1003.1 polynomial, but not neccesarily. So your source might’ve given you a version that differs from what you expected. Or, worse, be actually useless for the purpose.⁽¹⁾

GPTs are language models, which makes them suitable for getting a rough translation between computer languages. The key word here is “rough”. ChatGPT is like a tongues prodigy child, who can instantly translate between any two languages, but is absolutely devoid of understanding, what they just translated. If usage patterns do not capture the meaning, the translation is going to be as accurate as “English as she is spoke”. Computer code is very vulnerable to any imperfection. It also must retain logical connections between the elements. So ChatGPT is great as a source of hints. I would claim it beats any other available technology in that matter. But these are only hints: one must use them only as pointers to writing their own solution.

⁽¹⁾ You wrote, that you don’t care about the exact version as long as both are the same. This is not right. Most of the possible polynomials don’t provide good integrity verification.