03-rozwiazanie.js

@@ -0,0 +1,13 @@
+const crc = require("./crc.js");
+let message = process.argv[3];
+let flag = process.argv[2];
+switch (flag) {
+    case '-e':
+        console.log(crc.encode(message));
+        break;
+    case '-d':
+
+        break;
+    default:
+        throw "incorect flag"
+}

crc.js

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

polynomial.js

@@ -2,7 +2,14 @@ class Polynomial {
     constructor(mod, coefArray) {
         this.mod = mod;
         this.degree = (coefArray.length - 1);
-        this.coefficients = coefArray;
+
+        this.coefficients = Array.from(coefArray); //zeby nie przekazywać referencji
+        this.normalize();
+    }
+    normalize() {
+        while (this.coefficients && this.coefficients[this.coefficients.length - 1] == 0) {
+            this.coefficients.pop();
+        }
     }
 }