forked from kalmar/DALGLI0
64 lines
1.6 KiB
JavaScript
64 lines
1.6 KiB
JavaScript
let Polynomial = require('./polynomial.js');
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const to_bytes_ascii = a => a.charCodeAt(0);
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const from_bytes_ascii = a => String.fromCharCode(a);
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const to_bin = a => {
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var result = "";
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for (var i = 0; i < a.length; i++) {
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var bin = a[i].charCodeAt().toString(2);
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result += Array(8 - bin.length + 1).join("0") + bin;
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}
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return result;
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}
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const to_ascii = a => {
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a = a.join('');
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return String.fromCharCode(parseInt(a, 2));;
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}
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const fcs = m => {
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bits = m.map(to_bin); //message in binary
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bits = bits.join('').split('').reverse(); //reverse binary decoded message
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let M = new Polynomial.Class(2, bits);
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let L = new Polynomial.Class(2, new Array(16).fill(1));
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let X = new Polynomial.Class(2, [0, 1]);
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let X16 = Polynomial.power(X, 16);
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let G = new Polynomial.Class(2, [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1]); //jako ze można to od razu wymnożyć
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let fcs = Polynomial.multiply(X16, M);
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fcs = Polynomial.add(fcs,
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Polynomial.multiply(
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Polynomial.power(X, m.length * 8),
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L
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)
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)
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fcs = Polynomial.divide(fcs, G);
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for (let i = 0; i < 16 - fcs.coefficients.length; i++) fcs.coefficients.push(0);
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fcs.coefficients.reverse();
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return fcs.coefficients;
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}
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function encode(m) {
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m = m.split('');
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let res = fcs(m);
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let f1 = [];
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let f2 = [];
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for (let i = 0; i < res.length; i++) {
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if (i < 8) {
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f1.push(res[i]);
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} else {
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f2.push(res[i]);
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}
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}
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f1 = to_ascii(f1);
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f2 = to_ascii(f2);
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m.push(f1);
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m.push(f2);
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return m;
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}
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exports.encode = encode; |