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

@@ -1,20 +1,125 @@
 package com.tylkowski.crc;
 
-public class CrcTask {
+import java.util.Arrays;
+
+class CrcTask {
     private String message;
     private short[] messageAsShortArray;
     private short[] polyGenerator;
+    private String rawMessage;
 
-    public CrcTask(String message) {
-        this.message = message + "0000000000000000";
-        convertMessageToBinaryShortArray();
-        createGeneratingPoly();
-        swapPolyValues();
+    CrcTask(String message, String rawMessage) {
+        this.message = formatMessage(message) + "0000000000000000";
+        this.rawMessage = rawMessage;
+        createGeneratingPolynomial();
+    }
+
+    private String formatMessage(String message) {
+        int firstNonZeroVal = 0;
+        boolean found = false;
+        StringBuilder validString = new StringBuilder();
+        while (!found && firstNonZeroVal < message.length()) {
+            if (message.charAt(firstNonZeroVal) == 48) {
+                firstNonZeroVal++;
+            } else {
+                found = true;
+            }
+        }
+
+        for (int i = firstNonZeroVal; i < message.length(); i++) {
+            if (message.charAt(i) == 48) {
+                validString.append(0);
+            } else {
+                validString.append(1);
+            }
+        }
+        StringBuilder msg = new StringBuilder(validString.toString());
+        while (msg.length() % 8 != 0) {
+            msg.insert(0, "0");
+        }
+
+        return msg.toString();
+    }
+
+    private String generateFCS() {
+        while (true) {
+            if (messageAsShortArray[0] == 0) {
+                messageAsShortArray = Arrays.copyOfRange(messageAsShortArray, 1, messageAsShortArray.length);
+            } else {
+                short[] piece = Arrays.copyOfRange(messageAsShortArray, 0, Math.min(polyGenerator.length, messageAsShortArray.length));
+                if (piece.length < polyGenerator.length) {
+                    fillPolynomial(piece);
+                    return "" + getCharFromShortArray(piece, 0, 8) + getCharFromShortArray(piece, piece.length - 8, piece.length);
+                }
+                short[] remainder = calcXOR(piece, polyGenerator);
+                remainder = removeUnecessaryZeros(remainder);
+                createMessageFromRemainderAndPartFromOldMessage(remainder, remainder.length);
+            }
+
+
+        }
+
+    }
+
+    private void createMessageFromRemainderAndPartFromOldMessage(short[] remainder, int length) {
+        short[] tempArr = new short[remainder.length + messageAsShortArray.length - polyGenerator.length];
+        System.arraycopy(remainder, 0, tempArr, 0, length);
+        int diff = polyGenerator.length - remainder.length;
+        System.arraycopy(messageAsShortArray, length + diff, tempArr, length, messageAsShortArray.length - diff - length);
+        messageAsShortArray = tempArr;
+    }
+
+    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[] chunk, short[] polyGenerator) {
+        int a = Integer.parseInt(shortArrayToBinaryString(chunk), 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 char getCharFromShortArray(short[] chunk, int from, int to) {
+        short[] sign = Arrays.copyOfRange(chunk, from, to);
+        int character = Integer.parseInt(shortArrayToBinaryString(sign), 2);
+//        System.out.println(character);
+        return (char) character;
+    }
+
+    private void fillPolynomial(short[] chunk) {
+        while (chunk.length % 8 != 0) {
+            chunk = addZeroAtBeginningOfArray(chunk);
+        }
+    }
+
+    private short[] addZeroAtBeginningOfArray(short[] chunk) {
+        short[] letterTemp = new short[chunk.length + 1];
+        letterTemp[0] = 0;
+        System.arraycopy(chunk, 0, letterTemp, 1, chunk.length);
+        return letterTemp;
     }
 
     private void convertMessageToBinaryShortArray() {
         messageAsShortArray = new short[message.length()];
-        for (int i = 0; i < message.length(); i++) {
+        for (int i = 0; i < polyGenerator.length; i++) {
             if (message.charAt(i) == 48) {
                 messageAsShortArray[i] = 0;
             } else {
@@ -23,16 +128,38 @@ public class CrcTask {
         }
     }
 
-    private void createGeneratingPoly() {
-        polyGenerator = new short[16];
-        for (int i = 0; i < 16; i++) {
+    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 void swapPolynomialValues() {
+        for (int i = 0; i < polyGenerator.length - 1; i++) {
+            messageAsShortArray[i] = (short) ((messageAsShortArray[i] + 1) % 2);
+        }
     }
 
-    private void swapPolyValues() {
-        for (int i = 0; i < polyGenerator.length; i++) {
-            messageAsShortArray[i] = (short) ((messageAsShortArray[i] +  1) % 2);
-        }
+    String encode() {
+        convertMessageToBinaryShortArray();
+        swapPolynomialValues();
+        return rawMessage + generateFCS();
     }
 }

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

@@ -3,7 +3,8 @@ package com.tylkowski.crc;
 public class Main {
 
     public static void main(String[] args) {
-        CrcTask crcTask = new CrcTask(toBinary(args[0]));
+        CrcTask crcTask = new CrcTask(toBinary(args[0]), args[0]);
+        System.out.println(crcTask.encode());
     }
 
     private static String toBinary(String s) {