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

   1 /*
   2  * Svjatoslav Commons - shared library of common functionality.
   3  * Copyright ©2012-2019, 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 import java.io.IOException;
  14 import java.io.OutputStream;
  15
  16 /**
  17  * Write individual bits to the output stream.
  18  */
  19 public class BitOutputStream {
  20
  21     private final OutputStream outputStream;
  22     private int currentByte;
  23     private int currentBytePointer;
  24
  25     public BitOutputStream(final OutputStream outputStream) {
  26         currentByte = 0;
  27         currentBytePointer = 0;
  28         this.outputStream = outputStream;
  29     }
  30
  31     public void finishByte() throws IOException {
  32         if (currentBytePointer != 0) {
  33             outputStream.write(currentByte);
  34             currentBytePointer = 0;
  35         }
  36     }
  37
  38     public void storeBits(final int data, final int bitCount)
  39             throws IOException {
  40         for (int i = bitCount - 1; i >= 0; i--) {
  41
  42             int mask = 1;
  43             mask = mask << i;
  44
  45             final int currentBit = data & mask;
  46             currentByte = currentByte << 1;
  47
  48             if (currentBit != 0)
  49                 currentByte = currentByte | 1;
  50             currentBytePointer++;
  51
  52             if (currentBytePointer == 8) {
  53                 currentBytePointer = 0;
  54                 outputStream.write(currentByte);
  55                 currentByte = 0;
  56             }
  57         }
  58     }
  59
  60 }