src/main/java/eu/svjatoslav/commons/data/BitOutputStream.java

   1 /*
   2  * Svjatoslav Commons - shared library of common functionality.
   3  * Copyright ©2012-2014, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 3 of the GNU Lesser General Public License
   7  * or later as published by the Free Software Foundation.
   8  */
   9
  10 package eu.svjatoslav.commons.data;
  11
  12 /**
  13  * Write individual bits to the output stream.
  14  */
  15
  16 import java.io.IOException;
  17 import java.io.OutputStream;
  18
  19 public class BitOutputStream {
  20
  21         int currentByte;
  22         int currentBytePointer;
  23
  24         OutputStream outputStream;
  25
  26         public BitOutputStream(final OutputStream outputStream) {
  27                 currentByte = 0;
  28                 currentBytePointer = 0;
  29                 this.outputStream = outputStream;
  30         };
  31
  32         public void finishByte() throws IOException {
  33                 if (currentBytePointer != 0) {
  34                         outputStream.write(currentByte);
  35                         currentBytePointer = 0;
  36                 }
  37         }
  38
  39         public void storeBits(final int data, final int bitCount)
  40                         throws IOException {
  41                 for (int i = bitCount - 1; i >= 0; i--) {
  42
  43                         int mask = 1;
  44                         mask = mask << i;
  45
  46                         final int currentBit = data & mask;
  47                         currentByte = currentByte << 1;
  48
  49                         if (currentBit != 0)
  50                                 currentByte = currentByte | 1;
  51                         currentBytePointer++;
  52
  53                         if (currentBytePointer == 8) {
  54                                 currentBytePointer = 0;
  55                                 outputStream.write(currentByte);
  56                                 currentByte = 0;
  57                         }
  58                 }
  59         }
  60
  61         public void storeIntegerCompressed8(final int data) throws IOException {
  62                 if (data < 256) {
  63                         storeBits(0, 1);
  64                         storeBits(data, 8);
  65                 } else {
  66                         storeBits(1, 1);
  67                         storeBits(data, 32);
  68                 }
  69         }
  70
  71 }