forked from kalmar/DALGLI0
valid FCS output
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@ -1,7 +1,5 @@
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package com.tylkowski.crc;
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import java.lang.reflect.Field;
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import java.nio.charset.Charset;
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import java.util.Arrays;
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class CrcTask {
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@ -10,19 +8,12 @@ class CrcTask {
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private short[] polyGenerator;
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private String rawMessage;
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CrcTask(String message, String rawMessage) throws NoSuchFieldException, IllegalAccessException {
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setEncoding();
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CrcTask(String message) {
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this.rawMessage = message;
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this.message = formatMessage(toBinaryString(message)) + "0000000000000000";
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this.rawMessage = rawMessage;
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createGeneratingPolynomial();
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}
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private void setEncoding() throws NoSuchFieldException, IllegalAccessException {
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System.setProperty("file.encoding", "ISO-8859-1");
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Field charset = Charset.class.getDeclaredField("defaultCharset");
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charset.setAccessible(true);
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charset.set(null, null);
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}
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private String formatMessage(String message) {
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int firstNonZeroVal = 0;
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@ -59,7 +50,7 @@ class CrcTask {
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short[] piece = Arrays.copyOfRange(messageAsShortArray, 0, Math.min(polyGenerator.length, messageAsShortArray.length));
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if (piece.length < polyGenerator.length) {
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fillPolynomial(piece);
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return "" + getCharFromShortArray(piece, 0, 8) + getCharFromShortArray(piece, piece.length - 8, piece.length);
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return createTwoCharsOfFCS(piece);
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}
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short[] remainder = calcXOR(piece, polyGenerator);
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remainder = removeUnecessaryZeros(remainder);
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@ -69,6 +60,17 @@ class CrcTask {
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}
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private String createTwoCharsOfFCS(short[] piece) {
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short[] firstPiece = Arrays.copyOfRange(piece, 0, 8);
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short[] secondPiece = Arrays.copyOfRange(piece, piece.length - 8, piece.length);
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short[] mergedPieces = new short[firstPiece.length + secondPiece.length];
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for (int i = 0; i < firstPiece.length; i++) {
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mergedPieces[i] = firstPiece[i];
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mergedPieces[i + 8] = secondPiece[i];
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}
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return "0x" + Integer.toHexString(Integer.parseInt(shortArrayToBinaryString(mergedPieces), 2));
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}
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private short[] createMessageFromRemainderAndPartFromOldMessage(short[] remainder, short[] msg) {
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short[] tempArr = new short[remainder.length + msg.length - polyGenerator.length];
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System.arraycopy(remainder, 0, tempArr, 0, remainder.length);
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@ -106,12 +108,6 @@ class CrcTask {
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return binaryString.toString();
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}
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private char getCharFromShortArray(short[] piece, int from, int to) {
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short[] sign = Arrays.copyOfRange(piece, from, to);
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int character = Integer.parseInt(shortArrayToBinaryString(sign), 2);
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return (char) character;
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}
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private void fillPolynomial(short[] piece) {
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while (piece.length % 8 != 0) {
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piece = addZeroAtBeginningOfArray(piece);
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@ -171,7 +167,10 @@ class CrcTask {
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}
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boolean decode(String encodedString) {
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String fcs = encodedString.substring(encodedString.indexOf("0x"), encodedString.length());
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encodedString = encodedString.replace(fcs, "");
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encodedString = toBinaryString(encodedString);
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encodedString = encodedString + toBinaryStringFromHexValue(fcs);
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encodedString = fillPoly(encodedString);
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short[] encodedShortArray = convertBinaryStringToShortArray(encodedString);
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encodedShortArray = swapPolynomialValues(encodedShortArray);
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@ -194,6 +193,11 @@ class CrcTask {
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}
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}
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private String toBinaryStringFromHexValue(String hexString) {
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hexString = hexString.substring(2, hexString.length());
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return String.valueOf(Integer.toBinaryString(Integer.parseInt(hexString, 16)));
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}
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private String toBinaryString(String encodedString) {
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StringBuilder stringBuilder = new StringBuilder();
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for (int i = 0; i < encodedString.length(); i++) {
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@ -2,13 +2,13 @@ package com.tylkowski.crc;
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public class Main {
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public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
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public static void main(String[] args) {
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// in command line type "1" for mode and "b" for message
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// example "1" "b" -> this will encode string "b" and return FCS
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// example "2" "bXY" -> this will decode string "bXY" and return true if it is valid or false if not
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// X and Y - 1 and 2 character of FCS
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CrcTask crcTask = new CrcTask(args[1], args[1]);
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if(args[0].equals("1")) {
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// example "2" "bX" -> this will decode string "bX" and return true if it is valid or false if not
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// X - FCS
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CrcTask crcTask = new CrcTask(args[1]);
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if (args[0].equals("1")) {
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//create FCS
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System.out.println(crcTask.encode());
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} else if (args[0].equals("2")) {
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