src/main/java/eu/svjatoslav/imagesqueeze/codec/BitInputStream.java

   1 package eu.svjatoslav.imagesqueeze.codec;
   2
   3 /**
   4  * Read individual bits from the input stream.
   5  */
   6
   7 import java.io.IOException;
   8 import java.io.InputStream;
   9
  10 public class BitInputStream {
  11
  12
  13         int currentByte;
  14         int currentBytePointer = -1;
  15
  16         InputStream inputStream;
  17
  18         public BitInputStream(InputStream inputStream){
  19                 this.inputStream = inputStream;
  20         }
  21
  22         public int readBits(int bitCount) throws IOException {
  23
  24                 int readableByte = 0;
  25                 for (int i=0; i < bitCount; i++){
  26
  27                         readableByte = readableByte << 1;
  28
  29                         if (currentBytePointer == -1){
  30                                 currentBytePointer = 7;
  31                                 currentByte = inputStream.read();
  32                         }
  33
  34                         int mask = 1;
  35                         mask = mask << currentBytePointer;
  36
  37                         int currentBit = currentByte & mask;
  38
  39                         if (currentBit != 0){
  40                                 readableByte = readableByte | 1;
  41                         }
  42
  43                         currentBytePointer--;
  44                 }
  45                 return readableByte;
  46         }
  47
  48         public int readIntegerCompressed8() throws IOException{
  49                 if (readBits(1) == 0){
  50                         return readBits(8);
  51                 } else {
  52                         return readBits(32);
  53                 }
  54         }
  55
  56 }