add ReadMuller, Hamming coding, saving messages and info about every …

…message

App.js

@@ -27,6 +27,7 @@ export default class App extends React.Component {
     logout = () => {
         this.setState({screen: LOGIN_SCREEN, nickname: ''});
         AsyncStorage.removeItem('nickname');
+        AsyncStorage.removeItem('messages');
     };
 
     render() {

android/app/src/main/java/com/coder/BitArray.java

@@ -0,0 +1,275 @@
+/*
+ * Copyright 1997-2006 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package com.coder;
+
+import java.io.ByteArrayOutputStream;
+import java.util.Arrays;
+
+/**
+ * A packed array of booleans.
+ *
+ * @author Joshua Bloch
+ * @author Douglas Hoover
+ */
+
+public class BitArray {
+
+    private byte[] repn;
+    private int length;
+
+    private static final int BITS_PER_UNIT = 8;
+
+    private static int subscript(int idx) {
+        return idx / BITS_PER_UNIT;
+    }
+
+    private static int position(int idx) { // bits big-endian in each unit
+        return 1 << (BITS_PER_UNIT - 1 - (idx % BITS_PER_UNIT));
+    }
+
+    /**
+     * Creates a BitArray of the specified size, initialized to zeros.
+     */
+    public BitArray(int length) throws IllegalArgumentException {
+        if (length < 0) {
+            throw new IllegalArgumentException("Negative length for BitArray");
+        }
+
+        this.length = length;
+
+        repn = new byte[(length + BITS_PER_UNIT - 1)/BITS_PER_UNIT];
+    }
+
+
+    /**
+     * Creates a BitArray of the specified size, initialized from the
+     * specified byte array.  The most significant bit of a[0] gets
+     * index zero in the BitArray.  The array a must be large enough
+     * to specify a value for every bit in the BitArray.  In other words,
+     * 8*a.length <= length.
+     */
+    public BitArray(int length, byte[] a) throws IllegalArgumentException {
+
+        if (length < 0) {
+            throw new IllegalArgumentException("Negative length for BitArray");
+        }
+        if (a.length * BITS_PER_UNIT < length) {
+            throw new IllegalArgumentException("Byte array too short to represent " +
+                                               "bit array of given length");
+        }
+
+        this.length = length;
+
+        int repLength = ((length + BITS_PER_UNIT - 1)/BITS_PER_UNIT);
+        int unusedBits = repLength*BITS_PER_UNIT - length;
+        byte bitMask = (byte) (0xFF << unusedBits);
+
+        /*
+         normalize the representation:
+          1. discard extra bytes
+          2. zero out extra bits in the last byte
+         */
+        repn = new byte[repLength];
+        System.arraycopy(a, 0, repn, 0, repLength);
+        if (repLength > 0) {
+            repn[repLength - 1] &= bitMask;
+        }
+    }
+
+    /**
+     * Create a BitArray whose bits are those of the given array
+     * of Booleans.
+     */
+    public BitArray(boolean[] bits) {
+        length = bits.length;
+        repn = new byte[(length + 7)/8];
+
+        for (int i=0; i < length; i++) {
+            set(i, bits[i]);
+        }
+    }
+
+
+    /**
+     *  Copy constructor (for cloning).
+     */
+    private BitArray(BitArray ba) {
+        length = ba.length;
+        repn = ba.repn.clone();
+    }
+
+    /**
+     *  Returns the indexed bit in this BitArray.
+     */
+    public boolean get(int index) throws ArrayIndexOutOfBoundsException {
+        if (index < 0 || index >= length) {
+            throw new ArrayIndexOutOfBoundsException(Integer.toString(index));
+        }
+
+        return (repn[subscript(index)] & position(index)) != 0;
+    }
+
+    /**
+     *  Sets the indexed bit in this BitArray.
+     */
+    public void set(int index, boolean value)
+    throws ArrayIndexOutOfBoundsException {
+        if (index < 0 || index >= length) {
+            throw new ArrayIndexOutOfBoundsException(Integer.toString(index));
+        }
+        int idx = subscript(index);
+        int bit = position(index);
+
+        if (value) {
+            repn[idx] |= bit;
+        } else {
+            repn[idx] &= ~bit;
+        }
+    }
+
+    /**
+     * Returns the length of this BitArray.
+     */
+    public int length() {
+        return length;
+    }
+
+    /**
+     * Returns a Byte array containing the contents of this BitArray.
+     * The bit stored at index zero in this BitArray will be copied
+     * into the most significant bit of the zeroth element of the
+     * returned byte array.  The last byte of the returned byte array
+     * will be contain zeros in any bits that do not have corresponding
+     * bits in the BitArray.  (This matters only if the BitArray's size
+     * is not a multiple of 8.)
+     */
+    public byte[] toByteArray() {
+        return repn.clone();
+    }
+
+    public boolean equals(Object obj) {
+        if (obj == this) return true;
+        if (obj == null || !(obj instanceof BitArray)) return false;
+
+        BitArray ba = (BitArray) obj;
+
+        if (ba.length != length) return false;
+
+        for (int i = 0; i < repn.length; i += 1) {
+            if (repn[i] != ba.repn[i]) return false;
+        }
+        return true;
+    }
+
+    /**
+     * Return a boolean array with the same bit values a this BitArray.
+     */
+    public boolean[] toBooleanArray() {
+        boolean[] bits = new boolean[length];
+
+        for (int i=0; i < length; i++) {
+            bits[i] = get(i);
+        }
+        return bits;
+    }
+
+    /**
+     * Returns a hash code value for this bit array.
+     *
+     * @return  a hash code value for this bit array.
+     */
+    public int hashCode() {
+        int hashCode = 0;
+
+        for (int i = 0; i < repn.length; i++)
+            hashCode = 31*hashCode + repn[i];
+
+        return hashCode ^ length;
+    }
+
+
+    public Object clone() {
+        return new BitArray(this);
+    }
+
+
+    private static final byte[][] NYBBLE = {
+        { (byte)'0',(byte)'0',(byte)'0',(byte)'0'},
+        { (byte)'0',(byte)'0',(byte)'0',(byte)'1'},
+        { (byte)'0',(byte)'0',(byte)'1',(byte)'0'},
+        { (byte)'0',(byte)'0',(byte)'1',(byte)'1'},
+        { (byte)'0',(byte)'1',(byte)'0',(byte)'0'},
+        { (byte)'0',(byte)'1',(byte)'0',(byte)'1'},
+        { (byte)'0',(byte)'1',(byte)'1',(byte)'0'},
+        { (byte)'0',(byte)'1',(byte)'1',(byte)'1'},
+        { (byte)'1',(byte)'0',(byte)'0',(byte)'0'},
+        { (byte)'1',(byte)'0',(byte)'0',(byte)'1'},
+        { (byte)'1',(byte)'0',(byte)'1',(byte)'0'},
+        { (byte)'1',(byte)'0',(byte)'1',(byte)'1'},
+        { (byte)'1',(byte)'1',(byte)'0',(byte)'0'},
+        { (byte)'1',(byte)'1',(byte)'0',(byte)'1'},
+        { (byte)'1',(byte)'1',(byte)'1',(byte)'0'},
+        { (byte)'1',(byte)'1',(byte)'1',(byte)'1'}
+    };
+
+    private static final int BYTES_PER_LINE = 8;
+
+    /**
+     *  Returns a string representation of this BitArray.
+     */
+    public String toString() {
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+
+        for (int i = 0; i < repn.length - 1; i++) {
+            out.write(NYBBLE[(repn[i] >> 4) & 0x0F], 0, 4);
+            out.write(NYBBLE[repn[i] & 0x0F], 0, 4);
+
+            if (i % BYTES_PER_LINE == BYTES_PER_LINE - 1) {
+                out.write('\n');
+            } else {
+                out.write(' ');
+            }
+        }
+
+        // in last byte of repn, use only the valid bits
+        for (int i = BITS_PER_UNIT * (repn.length - 1); i < length; i++) {
+            out.write(get(i) ? '1' : '0');
+        }
+
+        return new String(out.toByteArray());
+
+    }
+
+    public BitArray truncate() {
+        for (int i=length-1; i>=0; i--) {
+            if (get(i)) {
+                return new BitArray(i+1, Arrays.copyOf(repn, (i + BITS_PER_UNIT)/BITS_PER_UNIT));
+            }
+        }
+        return new BitArray(1);
+    }
+
+}

android/app/src/main/java/com/coder/Hamming/Hamming74Coder.java

@@ -0,0 +1,98 @@
+/**
+ * This class used for Hamming(7,4) coding
+ * @author Pavel Kozlov
+ */
+
+package com.coder.Hamming;
+
+public class Hamming74Coder {
+
+    public Hamming74Coder() {
+    }
+
+    public byte[] coding(byte[] byteSequence){
+
+        int[] bits = new int[8 * byteSequence.length];
+        //converting all bytes to bits
+        for (int i = 0; i < bits.length; i++) {
+            bits[i] = (byteSequence[i / 8] >> (7 - i % 8)) & 1;
+        }
+
+
+        int[] codedBits = new int[7 * (bits.length/4)];
+
+
+        for (int i = 0; i < (bits.length/4); i++) {
+            int[] tempBits = code4bits(new int[]{bits[4*i],bits[4*i+1],bits[4*i+2],bits[4*i+3]});
+            codedBits[7*i] = tempBits[0];
+            codedBits[7*i+1] = tempBits[1];
+            codedBits[7*i+2] = tempBits[2];
+            codedBits[7*i+3] = tempBits[3];
+            codedBits[7*i+4] = tempBits[4];
+            codedBits[7*i+5] = tempBits[5];
+            codedBits[7*i+6] = tempBits[6];
+        }
+
+        if(codedBits.length % 8 != 0){
+            int[] oldcodedBits = codedBits;
+            codedBits = new int[(oldcodedBits.length/8+1) * 8];
+            int cnst = codedBits.length-oldcodedBits.length;
+            for (int i = 0; i < cnst; i++) {
+                codedBits[i] = 0;
+            }
+
+            for (int i = 0; i < oldcodedBits.length; i++) {
+                codedBits[cnst+i] = oldcodedBits[i];
+            }
+        }
+
+        byte[] encodedSequence = new byte[codedBits.length/8];
+
+        String str;
+        int count = 0;
+        //converting bits to bytes
+        for(int i=0; i < codedBits.length; i+=8){
+            str = new String();
+            for(int k=0; k<8; k++) {
+                str += codedBits[i+k];
+            }
+            int tr = Integer.parseInt(str, 2);
+            encodedSequence[count] = (byte) tr;
+            count++;
+        }
+
+        return encodedSequence;
+
+    }
+
+    private int[] code4bits (int[] initialBits){
+        int[] out_boolean = new int[]{0,0,0,0,0,0,0};
+        out_boolean[0] = initialBits[0];
+        out_boolean[1] = initialBits[0];
+        out_boolean[2] = initialBits[0];
+
+        out_boolean[0] += initialBits[1];
+        out_boolean[4] = initialBits[1];
+        out_boolean[3] += initialBits[1];
+
+        out_boolean[1] += initialBits[2];
+        out_boolean[5] = initialBits[2];
+        out_boolean[3] += initialBits[2];
+
+        out_boolean[0] += initialBits[3];
+        out_boolean[6] = initialBits[3];
+        out_boolean[1] += initialBits[3];
+        out_boolean[3] += initialBits[3];
+
+        out_boolean[0] %= 2;
+        out_boolean[1] %= 2;
+        out_boolean[2] %= 2;
+        out_boolean[3] %= 2;
+        out_boolean[4] %= 2;
+        out_boolean[5] %= 2;
+        out_boolean[6] %= 2;
+
+        return out_boolean;
+    }
+
+}