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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. import java.util.LinkedList;
  9.  
  10. // one class needs to have a main() method
  11. class VariableByte {
  12.  
  13.     static class Byte {
  14.         int[] abyte;
  15.  
  16.         Byte(){
  17.             abyte = new int[8];
  18.         }
  19.  
  20.         public void readInt(int n) {
  21.             // n must be less than 128 !!
  22.             String bin = Integer.toBinaryString(n);
  23.  
  24.             for(int i = 0 ; i < (8 - bin.length()) ; i++) {
  25.                 abyte[i] = 0;
  26.             }
  27.             for(int i = 0 ; i < bin.length() ; i++){
  28.                 abyte[i + (8 - bin.length())] = bin.charAt(i) - 48; // ASCII code for '0' is 48
  29.             }
  30.             //System.out.println(" Byte ***** " + this.toString());
  31.         }
  32.  
  33.         public void switchFirst(){
  34.             abyte[0] = 1;
  35.         }
  36.  
  37.         public int toInt(){
  38.             //System.out.println(" Byte ***** " + this.toString());
  39.             int res = 0;
  40.             for (int i = 0 ; i < 8 ; i++){
  41.                 res += abyte[i] * Math.pow(2, (7 - i));
  42.             }
  43.             //System.out.println(" Value ***** " + res);
  44.             return res;
  45.         }
  46.  
  47.         public String toString(){
  48.             String res ="";
  49.             for(int i = 0 ; i < 8 ; i++) {
  50.                 res += abyte[i];
  51.             }
  52.             return res;
  53.         }
  54.  
  55.     }
  56.  
  57.  
  58.     public static LinkedList<Byte> vbEncode(LinkedList<Integer> numbers) {
  59.         LinkedList<Byte> code = new LinkedList<Byte>();
  60.         while (numbers.size() > 0) {
  61.             int n = numbers.poll();
  62.             code.addAll(vbEncodeNumber(n));
  63.         }
  64.         return code;
  65.     }
  66.  
  67.     public static LinkedList<Byte> vbEncodeNumber(int n) {
  68.         LinkedList<Byte> bytestream = new LinkedList<Byte>();
  69.         int num = n;
  70.         while (true) {
  71.             Byte b = new Byte();
  72.             b.readInt(num % 128);
  73.             bytestream.addFirst(b);
  74.             if (num < 128) {break;}
  75.             num /= 128;     //right-shift of length 7 (128 = 2^7)
  76.         }
  77.         Byte last = bytestream.get(bytestream.size() - 1); //retrieving the last byte
  78.         last.switchFirst(); //setting the continuation bit to 1
  79.         return bytestream;
  80.     }
  81.  
  82.     public static LinkedList<Integer> vbDecode(LinkedList<Byte> code){
  83.         LinkedList<Integer> numbers = new LinkedList<Integer>();
  84.         int n = 0;
  85.         for(int i = 0 ; !(code.isEmpty()) ; i++){
  86.             Byte b = code.poll(); // read leading byte
  87.             //System.out.println(" Reading byte " + b.toString() );
  88.  
  89.             int  bi = b.toInt();  // decimal value of this byte
  90.             if (bi < 128) {       //continuation bit is set to 0
  91.                 n = 128 * n + bi;
  92.             } else {              // continuation bit is set to 1
  93.                 n = 128 * n + (bi - 128);
  94.                 numbers.add(n);   // number is stored
  95.                 n = 0;            // reset
  96.             }
  97.         }
  98.         return numbers;
  99.     }
  100.  
  101.     public static void main(String[] args) {
  102.         LinkedList<Integer> test = new LinkedList<Integer>();
  103.         test.add(825);
  104.         //test.add(Integer.parseInt(args[0]));
  105.         //test.add(1234);
  106.  
  107.         //System.out.println("Input values: 5 - 824 - 1234");
  108.  
  109.         LinkedList<Byte> code = vbEncode(test);
  110.  
  111.         System.out.println("Variable-byte code:");
  112.         for(int i = 0 ; i < code.size() ; i++){
  113.             System.out.print(code.get(i).toString() + " ");
  114.         }
  115.         System.out.println();
  116.  
  117.         LinkedList<Integer> decode = vbDecode(code);
  118.  
  119.         System.out.println("After decoding:");
  120.         for(int i = 0 ; i < decode.size() ; i++){
  121.             System.out.print(decode.get(i) + " ");
  122.         }
  123.         System.out.println();
  124.     }
  125. }
Success #stdin #stdout 0.05s 711168KB
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Standard input is empty
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Variable-byte code:
00000110 10111001 
After decoding:
825
https://ideone.com/BTjvtB
language:
Java (12.0.1)
created:
7 years ago
visibility:
public

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