Does this package have Python crc_hqx function equivalent? about crclib.dart

[postmasters]

You could change the initialValue of that class to 0x1021, perhaps by subclassing? This is how it is currently defined.

class Crc16Xmodem extends ParametricCrc {
  Crc16Xmodem()
      : super(
          16,
          0x1021,
          0x0000,   // <--- initial value.
          0x0000,
          inputReflected: false,
          outputReflected: false);
}

[postmasters]

Perhaps Crc16CcittTrue is the right one? There are many Crc16 with polynomial of 0x1021. See https://reveng.sourceforge.io/crc-catalogue/16.htm. You may have to try each one of them until you find a match. I'm feeling lucky with that class though.

[guyluz11]

Tested all and didn't find it

Did I missed something?.

[guyluz11]

Source

binascii.crc_hqx(data, value)

Compute a 16-bit CRC value of data, starting with value as the initial CRC, and return the result. This uses the CRC-CCITT polynomial x16 + x12 + x5 + 1, often represented as 0x1021. This CRC is used in the binhex4 format.

I don't understand much about this, maybe it will help.

[postmasters]

>>> binary_packet = [254, 240, 82, 0, 2, 50, 161, 0, 0, 0, 0, 0, 52, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 168, 187, 46, 97, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 240, 254, 28, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
>>> data = bytes(binary_packet)
>>> import binascii
>>> binascii.crc_hqx(data, 0)
16372

So looks like Crc16Xmodem is the one?

[guyluz11]

>>> binary_packet = [254, 240, 82, 0, 2, 50, 161, 0, 0, 0, 0, 0, 52, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 168, 187, 46, 97, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 240, 254, 28, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
>>> data = bytes(binary_packet)
>>> import binascii
>>> binascii.crc_hqx(data, 0)
16372

So looks like Crc16Xmodem is the one?

But it is not the same value as I gave

For example I give your binary_packet list in python

import binascii

binary_packet = [254, 240, 82, 0, 2, 50, 161, 0, 0, 0, 0, 0, 52, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 168, 187, 46, 97, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 240, 254, 28, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
result = binascii.crc_hqx(bytes(binary_packet), 0x1021)
print(result)

Result is equal to 58817

Same list in JavaScript

let TABLE = [
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
    0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
    0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
    0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
    0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
    0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
    0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
    0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
    0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
    0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
    0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
    0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
    0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
    0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
    0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
    0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
    0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
    0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
    0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
    0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
    0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
    0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
    0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
    0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
    0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
    0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
    0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
    0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
    0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
  ];

  
const crc16ccitt = defineCrc('ccitt', function(buf, previous) {
    let crc = typeof previous !== 'undefined' ? ~~previous : 0xffff;
    for (let index = 0; index < buf.length; index++) {
        const byte = buf[index];
        crc = (TABLE[((crc >> 8) ^ byte) & 0xff] ^ (crc << 8)) & 0xffff;
    }

    return crc;
});


var binary_packet = [ 254, 240, 82, 0, 2, 50, 161, 0, 0, 0, 0, 0, 52, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 168, 187, 46, 97, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 240, 254, 28, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
result = crc16ccitt(binary_packet, 0x1021)
console.log(result)

Result is 58817

But in dart

import 'package:crclib/catalog.dart';
import 'package:crclib/crclib.dart';

class NoNullSafetyMethods {
  static int getCrc16CcittTrue(List<int> listOfNumbers) {
    CrcValue z = Crc16CcittTrue().convert(listOfNumbers);
    CrcValue r = Crc16Ccitt().convert(listOfNumbers);
    CrcValue n = Crc16A().convert(listOfNumbers);
    CrcValue o = Crc16Acorn().convert(listOfNumbers);
    CrcValue p = Crc16Arc().convert(listOfNumbers);
    CrcValue w = Crc16AugCcitt().convert(listOfNumbers);
    CrcValue x = Crc16CcittFalse().convert(listOfNumbers);
    CrcValue a = Crc16GeniBus().convert(listOfNumbers);
    CrcValue b = Crc16Gsm().convert(listOfNumbers);
    CrcValue c = Crc16Ibm3740().convert(listOfNumbers);
    CrcValue d = Crc16IbmSdlc().convert(listOfNumbers);
    CrcValue e = Crc16IsoIec144433A().convert(listOfNumbers);
    CrcValue f = Crc16Kermit().convert(listOfNumbers);
    CrcValue g = Crc16Mcrf4xx().convert(listOfNumbers);
    CrcValue h = Crc16Riello().convert(listOfNumbers);
    CrcValue j = Crc16SpiFujitsu().convert(listOfNumbers);
    CrcValue l = Crc16Tms37157().convert(listOfNumbers);
    CrcValue m = Crc16Xmodem().convert(listOfNumbers);

    return int.parse(c.toString());
  }
}

void main(List args) async {
  List<int> binary_packet  = [ 254, 240, 82, 0, 2, 50, 161, 0, 0, 0, 0, 0, 52, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 168, 187, 46, 97, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 240, 254, 28, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];

  int a = NoNullSafetyMethods.getCrc16CcittTrue(binary_packet);
}

There is no line that translate this to 58817

Is there extra steps that I am missing?.
(I am using the nullsafety branch)

[guyluz11]

I see now from your + my example that it is Crc16Xmodem/Crc16Acorn.

We are getting different results in python because you use 0 and I use 0x1021

binascii.crc_hqx(bytes(data), 0)

binascii.crc_hqx(bytes(binary_packet), 0x1021)

I am not sure what is the name of the second parameter in my JavaScript example it is called previous.
So in this package by default it is using 0, is there a way to change it?.

[guyluz11]

Found it

crclib.dart/lib/catalog.dart

Line 617 in fd18467

0x0000,

If we change this to 0x1021 we get the 58817.

I can try to create pull request so that users will be able to change this value, tell me what you think.

[postmasters]

Normally initial values are either all 0s, or all 1s. For when you need a different initial value, subclassing ParametricCrc in your own code is more helpful, i.e. not meant for general population.

[guyluz11]

I have extended ParametricCrc with the new value

import 'package:crclib/crclib.dart';

class Crc16XmodemWith0x1021 extends ParametricCrc {
  Crc16XmodemWith0x1021()
      : super(16, 0x1021, 0x1021, 0x0000,
            inputReflected: false, outputReflected: false);
}

And now it works.

Thanks for all the help and support.