Calculate CRC16 CCITT FALSE in Google Apps Script [duplicate] - google-apps-script

Question

This question already has an answer here:
Calculate CRC-16/CCITT-FALSE in Google Apps Script
(1 answer)
Closed 1 year ago.
I have VBA code that calculate the CRC16 CCITT value of string but now i have plan to use it on Google Sheet, but didn't have any idea how it will be on google script
Function crc_ccitt_ffff(strParam As String) As String
Const CRC_POLY_CCITT As Long = &H1021&
Const CRC_START_CCITT_FFFF As Long = &HFFFF&
Dim crc_tabccitt(0 To 255) As Long, crc As Long, b() As Byte, c As Long, i As Long, j As Long
For i = 0 To 255
crc = 0
c = i * 256
For j = 0 To 7
If (crc Xor c) And 32768 Then
crc = (crc * 2) Xor CRC_POLY_CCITT
Else
crc = crc * 2
End If
c = c * 2
Next j
crc_tabccitt(i) = crc
Next i
b = strParam
crc = CRC_START_CCITT_FFFF
For i = 0 To UBound(b) Step 2
crc = (crc * 256) Xor crc_tabccitt(((crc \ 256) Xor b(i)) And 255)
crc = ((crc \ 65536) * 65536) Xor crc
Next i
crc_ccitt_ffff = Hex(crc)
End Function
String on Column A : 00020101021129370016A000000677010111021312345678901215802TH5406500.5553037646304
Expected Results on Column B(or any other column) : 3D85
Can anyone help me with this?

Answer 1

Okay. Just for fun I've managed to translate your VB code (not sure if the code is working) to JS. Here you go:
function crc_ccitt_ffff(str) {
const POLY = 0x1021;
const START = 0xFFFF;
function get_crc_for_num(i) {
var crc = 0;
var c = i * 256;
[...Array(8).keys()].forEach(_ => {
crc = ((crc ^ c) & 0x8000) ? (crc * 2) ^ POLY : crc * 2;
c = c * 2 });
return crc;
}
var table = [...Array(256).keys()].map((_,n) => get_crc_for_num(n));
var crc = START;
str.split('').forEach(c => {
crc = (crc * 0x100) ^ table[ ( ((crc / 0x100) >> 0) ^ c.charCodeAt() ) & 0xFF ];
crc = (((crc / 0x10000) >> 0) * 0x10000) ^ crc;
}
)
return crc.toString(16);
}
var str = '00020101021129370016A000000677010111021312345678901215802TH5406500.5553037646304';
console.log( crc_ccitt_ffff(str) ); // output 3d85
It gives the same result with your data and it gives the same results as here https://crccalc.com/
But, beware, I'm not a real coder and I know next to nothing about VB and CRC-16. So it makes sense to test my code thoroughly before rush it into production.
Here is the code for Google Spreadsheet:
function main() {
const sheet = SpreadsheetApp.getActiveSheet();
const range = sheet.getRange("A1:B");
const data = range.getValues().map(x => [x[0], crc_ccitt_ffff(x[0])]);
range.setValues(data);
}
function crc_ccitt_ffff(str) {
if (str == '') return;
const get_crc_for_num = (n) => {
let crc = 0;
let c = n * 256;
[...Array(8).keys()].forEach(_ => {
crc = ((crc ^ c) & 0x8000) ? (crc * 2) ^ 0x1021 : crc * 2;
c = c * 2;
});
return crc;
}
const table = [...Array(256).keys()].map((_,n) => get_crc_for_num(n));
var crc = 0xFFFF;
str.split('').forEach(c => {
crc = (crc * 0x100) ^ table[(((crc / 0x100) >> 0) ^ c.charCodeAt()) & 0xFF];
crc = (((crc / 0x10000) >> 0) * 0x10000) ^ crc;
});
return crc.toString(16);
}
It takes all strings from column 'A' and put their CRC-16 to column 'B'.

Answer 2

Not sure if my solution is correct. Here is the JS implementation of CRC-16/CCITT: Generate CRC16 CCITT False with Javascript?
It gives 7D133D85 which looks suspiciously like your expected result. I have no idea where the first four digits go in the VB code.
So I took that JS code and updated it a little bit this way:
var crcTable = [
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,
];
function crc16(str) {
var crc = 0xFFFF;
str.split('').forEach(c =>
crc = (crc << 8) ^ crcTable[(c.charCodeAt(0) ^ (crc >> 8)) & 0xFF]);
return crc.toString(16).toUpperCase();
}
var str = "00020101021129370016A000000677010111021312345678901215802TH5406500.5553037646304"
console.log(crc16(str)); // it gives 7d133d85
console.log(crc16(str).substring(4)); // it gives 3d85
As you can see, I use the substring(4) to get rid of the first four digits. Probably it's a stupid idea. Frankly, I'm not sure if this trick is applicable at all. You have to try it on your data.
Or to wait for someone who can translate accurately your VB code to JS. It doesn't look like an unsolvable task.