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

   1 /*
   2  * Svjatoslav Commons - shared library of common functionality. Author: Svjatoslav Agejenko.
   3  * This project is released under Creative Commons Zero (CC0) license.
   4  */
   5 package eu.svjatoslav.commons.data;
   6
   7
   8 import java.io.IOException;
   9 import java.io.OutputStream;
  10
  11 /**
  12  * Write individual bits to the output stream.
  13  */
  14 public class BitOutputStream {
  15
  16     private final OutputStream outputStream;
  17     private int currentByte;
  18     private int currentBytePointer;
  19
  20     public BitOutputStream(final OutputStream outputStream) {
  21         currentByte = 0;
  22         currentBytePointer = 0;
  23         this.outputStream = outputStream;
  24     }
  25
  26     public void finishByte() throws IOException {
  27         if (currentBytePointer != 0) {
  28             outputStream.write(currentByte);
  29             currentBytePointer = 0;
  30         }
  31     }
  32
  33     public void storeBits(final int data, final int bitCount)
  34             throws IOException {
  35         for (int i = bitCount - 1; i >= 0; i--) {
  36
  37             int mask = 1;
  38             mask = mask << i;
  39
  40             final int currentBit = data & mask;
  41             currentByte = currentByte << 1;
  42
  43             if (currentBit != 0)
  44                 currentByte = currentByte | 1;
  45             currentBytePointer++;
  46
  47             if (currentBytePointer == 8) {
  48                 currentBytePointer = 0;
  49                 outputStream.write(currentByte);
  50                 currentByte = 0;
  51             }
  52         }
  53     }
  54
  55 }