program now using polyomial class to calculate FCS

Zadanie-03/src/com/tylkowski/crc/CrcTask.java

@@ -3,158 +3,46 @@ package com.tylkowski.crc;
 import java.util.Arrays;
 
 class CrcTask {
-    private String message;
+    public CrcTask() {
-    private short[] messageAsShortArray;
-    private short[] polyGenerator;
-    private String rawMessage;
-
-    CrcTask(String message) {
-        this.rawMessage = message;
-        this.message = formatMessage(toBinaryString(message)) + "0000000000000000";
-        createGeneratingPolynomial();
     }
 
-
+    public Polynomial encode(String message) {
-    private String formatMessage(String message) {
+        Polynomial g = new Polynomial("[1,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,1]", 2); //G(X)
-        int firstNonZeroVal = 0;
+        Polynomial l = new Polynomial("[1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1]", 2); // L(X) 16 * 1
-        boolean found = false;
+        Polynomial m = new Polynomial("[" + formatMessageToBinaryArrayPolynomial(message) + "]", 2);
-        StringBuilder validString = new StringBuilder();
+        m.reverse();
-        while (!found && firstNonZeroVal < message.length()) {
+        Polynomial tmp2 = new Polynomial(l);
-            if (message.charAt(firstNonZeroVal) == 48) {
+        for (int i = 0; i < m.getSize(); i++) {
-                firstNonZeroVal++;
+            tmp2.append(0, 0);
-            } else {
-                found = true;
-            }
         }
-
+        Polynomial tmp = new Polynomial(m);
-        for (int i = firstNonZeroVal; i < message.length(); i++) {
+        for (int i = 0; i < 16; i++) {
-            if (message.charAt(i) == 48) {
+            tmp.append(0, 0);
-                validString.append(0);
-            } else {
-                validString.append(1);
-            }
         }
-        StringBuilder msg = new StringBuilder(validString.toString());
+        Polynomial sum = tmp.add(tmp2);
-        while (msg.length() % 8 != 0) {
+        Polynomial fcsPoly = sum.moduloPolyDivide(g);
-            msg.insert(0, "0");
+        while (fcsPoly.getSize() < 16) {
+            fcsPoly.append(0, 0);
         }
-
+        fcsPoly.reverse();
-        return msg.toString();
+        return fcsPoly;
     }
 
-    private String generateFCS() {
+    public String generateFCSChars(Polynomial poly) {
-        while (true) {
+        String binString = Arrays.toString(poly.getPolynomialArray());
-            if (messageAsShortArray[0] == 0) {
+        binString = binString.replace(",", "");
-                messageAsShortArray = Arrays.copyOfRange(messageAsShortArray, 1, messageAsShortArray.length);
+        binString = binString.replace("]", "");
-            } else {
+        binString = binString.replace("[", "");
-                short[] piece = Arrays.copyOfRange(messageAsShortArray, 0, Math.min(polyGenerator.length, messageAsShortArray.length));
+        binString = binString.replace(" ", "");
-                if (piece.length < polyGenerator.length) {
+        return "0x" + Integer.toHexString(Integer.parseInt(binString, 2));
-                    fillPolynomial(piece);
-                    return createTwoCharsOfFCS(piece);
-                }
-                short[] remainder = calcXOR(piece, polyGenerator);
-                remainder = removeUnecessaryZeros(remainder);
-                messageAsShortArray = createMessageFromRemainderAndPartFromOldMessage(remainder, messageAsShortArray);
-            }
-        }
-
     }
 
-    private String createTwoCharsOfFCS(short[] piece) {
+    private String formatMessageToBinaryArrayPolynomial(String message) {
-        short[] firstPiece = Arrays.copyOfRange(piece, 0, 8);
+        String msgBinString = toBinaryString(message);
-        short[] secondPiece = Arrays.copyOfRange(piece, piece.length - 8, piece.length);
+        msgBinString = msgBinString.replace("1", "1,");
-        short[] mergedPieces = new short[firstPiece.length + secondPiece.length];
+        msgBinString = msgBinString.replace("0", "0,");
-        for (int i = 0; i < firstPiece.length; i++) {
+        msgBinString = msgBinString.substring(0, msgBinString.length() - 1);
-            mergedPieces[i] = firstPiece[i];
+        return msgBinString;
-            mergedPieces[i + 8] = secondPiece[i];
-        }
-        return "0x" + Integer.toHexString(Integer.parseInt(shortArrayToBinaryString(mergedPieces), 2));
-    }
-
-    private short[] createMessageFromRemainderAndPartFromOldMessage(short[] remainder, short[] msg) {
-        short[] tempArr = new short[remainder.length + msg.length - polyGenerator.length];
-        System.arraycopy(remainder, 0, tempArr, 0, remainder.length);
-        int diff = polyGenerator.length - remainder.length;
-        System.arraycopy(msg, remainder.length + diff, tempArr, remainder.length, msg.length - diff - remainder.length);
-        msg = tempArr;
-        return msg;
-    }
-
-    private short[] removeUnecessaryZeros(short[] remainder) {
-        int firstNonZeroVal = 0;
-        boolean found = false;
-        while (!found && firstNonZeroVal < remainder.length) {
-            if (remainder[firstNonZeroVal] == 0) {
-                firstNonZeroVal++;
-            } else {
-                found = true;
-            }
-        }
-        return Arrays.copyOfRange(remainder, firstNonZeroVal, remainder.length);
-    }
-
-    private short[] calcXOR(short[] piece, short[] polyGenerator) {
-        int a = Integer.parseInt(shortArrayToBinaryString(piece), 2);
-        int b = Integer.parseInt(shortArrayToBinaryString(polyGenerator), 2);
-        String binaryString = Integer.toBinaryString(a ^ b);
-        return convertBinaryStringToShortArray(binaryString);
-    }
-
-    private String shortArrayToBinaryString(short[] value) {
-        StringBuilder binaryString = new StringBuilder();
-        for (Short a : value) {
-            binaryString.append(a);
-        }
-        return binaryString.toString();
-    }
-
-    private void fillPolynomial(short[] piece) {
-        while (piece.length % 8 != 0) {
-            piece = addZeroAtBeginningOfArray(piece);
-        }
-    }
-
-    private short[] addZeroAtBeginningOfArray(short[] piece) {
-        short[] tempArray = new short[piece.length + 1];
-        tempArray[0] = 0;
-        System.arraycopy(piece, 0, tempArray, 1, piece.length);
-        return tempArray;
-    }
-
-    private short[] convertBinaryStringToShortArray(String binaryString) {
-        short[] shortArray = new short[binaryString.length()];
-        for (int i = 0; i < binaryString.length(); i++) {
-            if (binaryString.charAt(i) == 48) {
-                shortArray[i] = 0;
-            } else {
-                shortArray[i] = 1;
-            }
-        }
-        return shortArray;
-    }
-
-    private void createGeneratingPolynomial() {
-        polyGenerator = new short[17];
-        for (int i = 0; i < 17; i++) {
-            polyGenerator[i] = 0;
-        }
-        polyGenerator[0] = 1;
-        polyGenerator[4] = 1;
-        polyGenerator[11] = 1;
-        polyGenerator[16] = 1;
-    }
-
-    private short[] swapPolynomialValues(short[] poly) {
-        for (int i = 0; i < polyGenerator.length - 1; i++) {
-            poly[i] = (short) ((poly[i] + 1) % 2);
-        }
-        return poly;
-    }
-
-    String encode() {
-        messageAsShortArray = convertBinaryStringToShortArray(message);
-        messageAsShortArray = swapPolynomialValues(messageAsShortArray);
-        return rawMessage + generateFCS();
     }
 
     private String letterToBinaryString(char letter) {
@@ -166,33 +54,6 @@ class CrcTask {
         return binaryString.toString();
     }
 
-    boolean decode(String encodedString) {
-        String fcs = encodedString.substring(encodedString.indexOf("0x"), encodedString.length());
-        encodedString = encodedString.replace(fcs, "");
-        encodedString = toBinaryString(encodedString);
-        encodedString = encodedString + toBinaryStringFromHexValue(fcs);
-        encodedString = fillPoly(encodedString);
-        short[] encodedShortArray = convertBinaryStringToShortArray(encodedString);
-        encodedShortArray = swapPolynomialValues(encodedShortArray);
-        while (true) {
-            if (!shortArrayContains(encodedShortArray, 1)) {
-                return true;
-            }
-            if (encodedShortArray[0] == 0) {
-                encodedShortArray = Arrays.copyOfRange(encodedShortArray, 1, encodedShortArray.length);
-            } else {
-                short[] piece = Arrays.copyOfRange(encodedShortArray, 0, Math.min(polyGenerator.length, encodedShortArray.length));
-                if (piece.length < polyGenerator.length) {
-                    return false;
-                }
-
-                short[] remainder = calcXOR(piece, polyGenerator);
-                remainder = removeUnecessaryZeros(remainder);
-                encodedShortArray = createMessageFromRemainderAndPartFromOldMessage(remainder, encodedShortArray);
-            }
-        }
-    }
-
     private String toBinaryStringFromHexValue(String hexString) {
         hexString = hexString.substring(2, hexString.length());
         return String.valueOf(Integer.toBinaryString(Integer.parseInt(hexString, 16)));
@@ -206,20 +67,31 @@ class CrcTask {
         return stringBuilder.toString();
     }
 
-    private boolean shortArrayContains(short[] encodedShortArray, int value) {
+    public boolean decode(String messageString) {
-        for (short item : encodedShortArray) {
+        Polynomial g = new Polynomial("[1,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,1]", 2);
-            if (item == value) {
+        Polynomial l = new Polynomial("[1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1]", 2);
-                return true;
+        String fcs = messageString.substring(messageString.indexOf("0x"), messageString.length());
-            }
+        messageString = messageString.replace(fcs, "");
+        messageString = toBinaryString(messageString);
+        String messageAsBinaryString = messageString + toBinaryStringFromHexValue(fcs);
+        Polynomial message = new Polynomial("[" + toPolynomialStringFromBinaryString(messageAsBinaryString) + "]", 2);
+        message.reverse();
+        for (int i = 0; i < 16; i++) {
+            message.append(0,0);
         }
-        return false;
+        Polynomial tmp = new Polynomial(l);
+        for (int i = 0; i < messageAsBinaryString.length(); i++) {
+            tmp.append(0, 0);
+        }
+        Polynomial sum = message.add(tmp);
+        message = sum.moduloPolyDivide(g);
+        return message.haveOnlyZeros();
     }
 
-    private String fillPoly(String encodedString) {
+    private String toPolynomialStringFromBinaryString(String msgBinString) {
-        StringBuilder stringBuilder = new StringBuilder(encodedString);
+        msgBinString = msgBinString.replace("1", "1,");
-        while (stringBuilder.length() % 8 != 0) {
+        msgBinString = msgBinString.replace("0", "0,");
-            stringBuilder.insert(0, "0");
+        msgBinString = msgBinString.substring(0, msgBinString.length() - 1);
-        }
+        return msgBinString;
-        return stringBuilder.toString();
     }
 }

Zadanie-03/src/com/tylkowski/crc/Main.java

@@ -7,13 +7,15 @@ public class Main {
         // example "1" "b" -> this will encode string "b" and return FCS
         // example "2" "bX" -> this will decode string "bX" and return true if it is valid or false if not
 		// X - FCS
-        CrcTask crcTask = new CrcTask(args[1]);
+        CrcTask crcTask = new CrcTask();
         if (args[0].equals("1")) {
             //create FCS
-            System.out.println(crcTask.encode());
+            System.out.println(args[1] + crcTask.generateFCSChars(crcTask.encode(args[1])));
         } else if (args[0].equals("2")) {
             // check fcs
-            if (args[1].length() >= 3) System.out.println(crcTask.decode(args[1]));
+            if (args[1].length() >= 3) {
+                System.out.println(crcTask.decode(args[1]));
+            }
         }
 
     }

Zadanie-03/src/com/tylkowski/crc/Polynomial.java

@@ -0,0 +1,182 @@
+package com.tylkowski.crc;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class Polynomial {
+    private int[] polynomial;
+    private int modulo;
+
+    public Polynomial(String polyString, int modulo) {
+        this.polynomial = parsePolynomialString(polyString);
+        this.modulo = modulo;
+    }
+
+    public Polynomial(int[] polynomial, int modulo) {
+        this.polynomial = polynomial;
+        this.modulo = modulo;
+    }
+
+    public Polynomial(List<Integer> polynomial, int modulo) {
+        this.polynomial = polynomial.stream().mapToInt(i -> i).toArray();
+        this.modulo = modulo;
+    }
+
+    public Polynomial(Polynomial polynomial) {
+        this.polynomial = polynomial.getPolynomialArray();
+        this.modulo = polynomial.getModulo();
+    }
+
+
+    public void append(int index, int value) {
+        ArrayList<Integer> poly = asArrayList();
+        poly.add(index, value);
+        polynomial = poly.stream().mapToInt(i -> i).toArray();
+    }
+
+
+    private int[] parsePolynomialString(String poly) {
+        poly = poly.substring(1, poly.length() - 1);
+        return Arrays.stream(poly.split(",\\s*")).map(String::trim).mapToInt(Integer::parseInt).toArray();
+    }
+
+    public int[] getPolynomialArray() {
+        return polynomial;
+    }
+
+
+    public int getModulo() {
+        return modulo;
+    }
+
+
+    public Polynomial subtract(Polynomial polyTwo) {
+        Polynomial polyOne = new Polynomial(this);
+        ArrayList<Integer> result = new ArrayList<>();
+        for (int i = 0; i < polyOne.getSize(); ++i) {
+            if (i < polyTwo.getSize()) {
+                result.add(Math.floorMod(polyOne.coeffAt(i) - polyTwo.coeffAt(i), modulo));
+            } else {
+                result.add(polyOne.coeffAt(i));
+            }
+        }
+        return new Polynomial(result, modulo);
+    }
+
+    public int getSize() {
+        return polynomial.length;
+    }
+
+    public int coeffAt(int i) {
+        return polynomial[i];
+    }
+
+    public void set(int index, int value) {
+        polynomial[index] = value;
+    }
+
+    public List<Integer> asList() {
+        return Arrays.stream(polynomial).boxed().collect(Collectors.toList());
+    }
+
+    public ArrayList<Integer> asArrayList() {
+        ArrayList<Integer> result = new ArrayList<>();
+        for (int i = 0; i < polynomial.length; i++) {
+            result.add(polynomial[i]);
+        }
+        return result;
+    }
+
+    public Polynomial add(Polynomial polyTwo) {
+        int size = Math.max(polynomial.length, polyTwo.getSize());
+        int[] result = new int[size];
+        for (int i = 0; i < size; i++) {
+            int res = 0;
+            if (i >= polynomial.length) {
+                res = polyTwo.coeffAt(i);
+            }
+            if (i >= polyTwo.getSize()) {
+                res = polynomial[i];
+            }
+            if (i < polynomial.length && i < polyTwo.getSize()) {
+                res = polynomial[i] + polyTwo.coeffAt(i);
+            }
+            result[i] = res;
+        }
+        Polynomial resultPoly = new Polynomial(result, modulo);
+        resultPoly = resultPoly.moduloPoly(resultPoly);
+        return resultPoly;
+    }
+
+    public Polynomial multiplyByNumber(int a) {
+        ArrayList<Integer> result = new ArrayList<>();
+        for (int i = 0; i < polynomial.length; i++) {
+            result.add((polynomial[i] * a) % modulo);
+        }
+        return new Polynomial(result, modulo);
+    }
+
+    public boolean haveOnlyZeros() {
+        return !asArrayList().contains(1);
+    }
+
+    public Polynomial moduloPoly(Polynomial poly) {
+        for (int i = 0; i < poly.getSize(); i++) {
+            while (poly.coeffAt(i) < 0) {
+                poly.getPolynomialArray()[i] = poly.getPolynomialArray()[i] + modulo;
+            }
+            poly.getPolynomialArray()[i] = poly.getPolynomialArray()[i] % modulo;
+        }
+        return poly;
+    }
+
+    private int findZero(int a, int b, int modulo) {
+        for (int i = 0; i <= modulo; i++) {
+            if ((a + (-(b * i))) == 0) {
+                return i;
+            }
+        }
+        return -1;
+    }
+    public Polynomial moduloPolyDivide(Polynomial polyTwo) {
+        Polynomial polyOne = new Polynomial(this);
+        Polynomial quotient = new Polynomial("[0]", polyOne.getModulo());
+        Polynomial rem = new Polynomial(polyOne);
+        Polynomial tmpPoly;
+        int polyOneIterator = polyOne.getSize() - 1;
+        int polyTwoIterator = polyTwo.getSize() - 1;
+        for (int i = 0; i < polyOneIterator - polyTwoIterator; i++) {
+            quotient.append(0, 0);
+        }
+        int quotientIterator = quotient.getSize() - 1;
+        int tmpZero;
+        while (polyOneIterator >= polyTwoIterator) {
+            tmpZero = findZero(rem.coeffAt(polyOneIterator), polyTwo.coeffAt(polyTwoIterator), polyOne.getModulo());
+            quotient.set(quotientIterator--, tmpZero);
+            tmpPoly = polyTwo.multiplyByNumber(tmpZero);
+            while (tmpPoly.getSize() <= polyOneIterator) {
+                tmpPoly.append(0, 0);
+            }
+            rem = rem.subtract(tmpPoly);
+            polyOneIterator--;
+        }
+        return rem;
+    }
+
+    @Override
+    public String toString() {
+        return "Polynomial{" +
+                "polynomial=" + Arrays.toString(polynomial) +
+                ", modulo=" + modulo +
+                '}';
+    }
+
+    public void reverse() {
+        int[] temp = Arrays.copyOf(getPolynomialArray(), getPolynomialArray().length);
+        for (int i = 0; i < temp.length; i++) {
+            polynomial[i] = temp[temp.length - i - 1];
+        }
+    }
+}