Сrc8 control

Just simple library to encode and decode data with crc8 tail.
I think it is an important to use it for the open transfered data such as 433 MGz modules HC-12.
The lib:

var Coding = function () {
	this.crc8_table = [
		  0x00, 0x5E, 0xBC, 0xE2, 0x61, 0x3F, 0xDD, 0x83,
		  0xC2, 0x9C, 0x7E, 0x20, 0xA3, 0xFD, 0x1F, 0x41,
		  0x9D, 0xC3, 0x21, 0x7F, 0xFC, 0xA2, 0x40, 0x1E,
		  0x5F, 0x01, 0xE3, 0xBD, 0x3E, 0x60, 0x82, 0xDC,
		  0x23, 0x7D, 0x9F, 0xC1, 0x42, 0x1C, 0xFE, 0xA0,
		  0xE1, 0xBF, 0x5D, 0x03, 0x80, 0xDE, 0x3C, 0x62,
		  0xBE, 0xE0, 0x02, 0x5C, 0xDF, 0x81, 0x63, 0x3D,
		  0x7C, 0x22, 0xC0, 0x9E, 0x1D, 0x43, 0xA1, 0xFF,
		  0x46, 0x18, 0xFA, 0xA4, 0x27, 0x79, 0x9B, 0xC5,
		  0x84, 0xDA, 0x38, 0x66, 0xE5, 0xBB, 0x59, 0x07,
		  0xDB, 0x85, 0x67, 0x39, 0xBA, 0xE4, 0x06, 0x58,
		  0x19, 0x47, 0xA5, 0xFB, 0x78, 0x26, 0xC4, 0x9A,
		  0x65, 0x3B, 0xD9, 0x87, 0x04, 0x5A, 0xB8, 0xE6,
		  0xA7, 0xF9, 0x1B, 0x45, 0xC6, 0x98, 0x7A, 0x24,
		  0xF8, 0xA6, 0x44, 0x1A, 0x99, 0xC7, 0x25, 0x7B,
		  0x3A, 0x64, 0x86, 0xD8, 0x5B, 0x05, 0xE7, 0xB9,
		  0x8C, 0xD2, 0x30, 0x6E, 0xED, 0xB3, 0x51, 0x0F,
		  0x4E, 0x10, 0xF2, 0xAC, 0x2F, 0x71, 0x93, 0xCD,
		  0x11, 0x4F, 0xAD, 0xF3, 0x70, 0x2E, 0xCC, 0x92,
		  0xD3, 0x8D, 0x6F, 0x31, 0xB2, 0xEC, 0x0E, 0x50,
		  0xAF, 0xF1, 0x13, 0x4D, 0xCE, 0x90, 0x72, 0x2C,
		  0x6D, 0x33, 0xD1, 0x8F, 0x0C, 0x52, 0xB0, 0xEE,
		  0x32, 0x6C, 0x8E, 0xD0, 0x53, 0x0D, 0xEF, 0xB1,
		  0xF0, 0xAE, 0x4C, 0x12, 0x91, 0xCF, 0x2D, 0x73,
		  0xCA, 0x94, 0x76, 0x28, 0xAB, 0xF5, 0x17, 0x49,
		  0x08, 0x56, 0xB4, 0xEA, 0x69, 0x37, 0xD5, 0x8B,
		  0x57, 0x09, 0xEB, 0xB5, 0x36, 0x68, 0x8A, 0xD4,
		  0x95, 0xCB, 0x29, 0x77, 0xF4, 0xAA, 0x48, 0x16,
		  0xE9, 0xB7, 0x55, 0x0B, 0x88, 0xD6, 0x34, 0x6A,
		  0x2B, 0x75, 0x97, 0xC9, 0x4A, 0x14, 0xF6, 0xA8,
		  0x74, 0x2A, 0xC8, 0x96, 0x15, 0x4B, 0xA9, 0xF7,
		  0xB6, 0xE8, 0x0A, 0x54, 0xD7, 0x89, 0x6B, 0x35,
		 ];
};
Coding.prototype.get_crc8 = function (data) {
	function expl(dt) {
		var m = [];
		for (var i = 0; i < dt.length; i++) {
			m.push((dt[i]).charCodeAt(0));
		}
		return m;
	}
	var dat = (expl(data));
	var crc = 0;
	for (var i = 0; i < dat.length; i++) {
		var dig = dat[i];
		crc = this.crc8_table[dig^crc];
	}
	return crc;
};

Coding.prototype.decode = function (data) {
	var place = data.indexOf("#");
	if (place < 8) {
		return 'NoCRC:#';
	}
	var dat = data.substring(0, place + 1);
	var crcstr = data.substring(data.indexOf("#") + 1);
	if (crcstr.length > 3) {
		return 'NoCRC:long';
	}

	var crc = parseInt(crcstr, 10);
	var control = this.get_crc8(dat);
	if (crc == control) {
		//console.log('Good!');
		var dt = data.substring(0, data.indexOf("}") + 1);
		return dt;

	} else {
		//console.log('Bad!');
		return 'NoCRC';
	}
};
Coding.prototype.encode = function (data) {
	var first = (Math.random() * 255).toFixed(0);
	var part = data + first + '#';
	var end = this.get_crc8(part).toFixed(0);
	var all = part + end;
	return all;
};

exports.connect = function () {
	  return new Coding();
};

1 Attachment

That's great, thanks!

If you're interested, if you re-wrote the beginning as:

var Coding = function () {
};
Coding.prototype.crc8_table = new Uint8Array([
          0x00, 0x5E, 0xBC, 0xE2, 0x61, 0x3F, 0xDD, 0x83,
          0xC2, 0x9C, 0x7E, 0x20, 0xA3, 0xFD, 0x1F, 0x41,
          0x9D, 0xC3, 0x21, 0x7F, 0xFC, 0xA2, 0x40, 0x1E,
          0x5F, 0x01, 0xE3, 0xBD, 0x3E, 0x60, 0x82, 0xDC,
          0x23, 0x7D, 0x9F, 0xC1, 0x42, 0x1C, 0xFE, 0xA0,
          0xE1, 0xBF, 0x5D, 0x03, 0x80, 0xDE, 0x3C, 0x62,
          0xBE, 0xE0, 0x02, 0x5C, 0xDF, 0x81, 0x63, 0x3D,
          0x7C, 0x22, 0xC0, 0x9E, 0x1D, 0x43, 0xA1, 0xFF,
          0x46, 0x18, 0xFA, 0xA4, 0x27, 0x79, 0x9B, 0xC5,
          0x84, 0xDA, 0x38, 0x66, 0xE5, 0xBB, 0x59, 0x07,
          0xDB, 0x85, 0x67, 0x39, 0xBA, 0xE4, 0x06, 0x58,
          0x19, 0x47, 0xA5, 0xFB, 0x78, 0x26, 0xC4, 0x9A,
          0x65, 0x3B, 0xD9, 0x87, 0x04, 0x5A, 0xB8, 0xE6,
          0xA7, 0xF9, 0x1B, 0x45, 0xC6, 0x98, 0x7A, 0x24,
          0xF8, 0xA6, 0x44, 0x1A, 0x99, 0xC7, 0x25, 0x7B,
          0x3A, 0x64, 0x86, 0xD8, 0x5B, 0x05, 0xE7, 0xB9,
          0x8C, 0xD2, 0x30, 0x6E, 0xED, 0xB3, 0x51, 0x0F,
          0x4E, 0x10, 0xF2, 0xAC, 0x2F, 0x71, 0x93, 0xCD,
          0x11, 0x4F, 0xAD, 0xF3, 0x70, 0x2E, 0xCC, 0x92,
          0xD3, 0x8D, 0x6F, 0x31, 0xB2, 0xEC, 0x0E, 0x50,
          0xAF, 0xF1, 0x13, 0x4D, 0xCE, 0x90, 0x72, 0x2C,
          0x6D, 0x33, 0xD1, 0x8F, 0x0C, 0x52, 0xB0, 0xEE,
          0x32, 0x6C, 0x8E, 0xD0, 0x53, 0x0D, 0xEF, 0xB1,
          0xF0, 0xAE, 0x4C, 0x12, 0x91, 0xCF, 0x2D, 0x73,
          0xCA, 0x94, 0x76, 0x28, 0xAB, 0xF5, 0x17, 0x49,
          0x08, 0x56, 0xB4, 0xEA, 0x69, 0x37, 0xD5, 0x8B,
          0x57, 0x09, 0xEB, 0xB5, 0x36, 0x68, 0x8A, 0xD4,
          0x95, 0xCB, 0x29, 0x77, 0xF4, 0xAA, 0x48, 0x16,
          0xE9, 0xB7, 0x55, 0x0B, 0x88, 0xD6, 0x34, 0x6A,
          0x2B, 0x75, 0x97, 0xC9, 0x4A, 0x14, 0xF6, 0xA8,
          0x74, 0x2A, 0xC8, 0x96, 0x15, 0x4B, 0xA9, 0xF7,
          0xB6, 0xE8, 0x0A, 0x54, 0xD7, 0x89, 0x6B, 0x35,
         ]);

Then it would use a lot less RAM

I use the library by the simple code:

var crc8 = require("crc8").connect();

var dt = '{"ab":22}';
var codeddt = crc8.encode(dt);
// > {"ab":22}212#135

var decdt = crc8.decode(codeddt);
console.log("crc8 Report = ", decdt);
// > crc8 Report =  {"ab":22}
if (decdt.indexOf("CRC") > 0 ){
    return;
}
else {
    // yours code 
}

Then it would use a lot less RAM

Thanks a lot! I am the beginner learning and enjoy Espruino and JS :-)