crc8.js

// works!
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: not #';
		}
		//var dat = data.substring(0, data.indexOf("#")+1);
		var dat = data.substring(0, place+1);
		var crcstr = data.substring(data.indexOf("#")+1);
		if (crcstr.length > 3) {
			return 'NoCRC: long crc';
		}
		
		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: bad crc';
		}
	};

	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();
};