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Java Source format, 12 months 7 hours old, and 137 hits.

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Anonymous
Wednesday, May 23rd, 2012 at 4:47:25pm MDT 

  1. package TDC.Compression.Arithmetic;
  2.  
  3. import java.io.InputStream;
  4. import java.io.IOException;
  5.  
  6. /**
  7. * Reads input from an underlying input stream a bit at a time. Bits are
  8. * returned as booleans, with
  9. * <code>true=1</code> and
  10. * <code>false=0</code>.
  11. * @author Inna Tuzhikova
  12. *
  13. */
  14. public final class BitInput {
  15.  
  16.     /**
  17.      * Constructs a bit input from an underlying input stream.
  18.      *
  19.      * @param in Input stream backing this bit input.
  20.      * @throws IOException If there is an exception reading from the specified
  21.      * input stream.
  22.      */
  23.     public BitInput(InputStream in) throws IOException {
  24.         _in = in;
  25.         readAhead();
  26.     }
  27.  
  28.     /**
  29.      * Returns number of bits available for reading. Will always be
  30.      * <code>0</code> or
  31.      * <code>1</code>.
  32.      *
  33.      * @return Number of bits available for reading.
  34.      * @throws IOException If there is an exception checking available bytes in
  35.      * the underlying input stream.
  36.      */
  37.     public long available() throws IOException {
  38.         return endOfStream() ? 0 : 1;
  39.     }
  40.  
  41.     /**
  42.      * Closes the underlying input stream.
  43.      *
  44.      * @throws IOException If there is an exception closing the underlying input
  45.      * stream.
  46.      */
  47.     public void close() throws IOException {
  48.         _in.close();
  49.     }
  50.  
  51.     /**
  52.      * Returns
  53.      * <code>true</code> if all of the available bits have been read.
  54.      *
  55.      * @return
  56.      * <code>true</code> if all of the available bits have been read.
  57.      */
  58.     public boolean endOfStream() {
  59.         return _endOfStream;
  60.     }
  61.  
  62.     /**
  63.      * Reads the next bit from the input stream. Returns garbage if reading
  64.      * while available() is false.
  65.      *
  66.      * @return The boolean value of the next bit,
  67.      * <code>true</code>=1,
  68.      * <code>false</code>=0.
  69.      * @throws IOException If there is an exception reading a byte from the
  70.      * underlying stream.
  71.      */
  72.     public boolean readBit() throws IOException {
  73.         if (_nextBitIndex > 0) {
  74.             // inspects bit in buffered byte
  75.             return ((_nextByte & (1 << _nextBitIndex--)) != 0);
  76.         }
  77.         // on last bit in byte; buffer new byte
  78.         boolean result = ((_nextByte & 1) != 0);
  79.         readAhead();
  80.         return result;
  81.     }
  82.     /**
  83.      * Underlying input stream.
  84.      */
  85.     private final InputStream _in;
  86.     /**
  87.      * Buffered byte from which bits are read.
  88.      */
  89.     private int _nextByte; // implied = 0;
  90.     /**
  91.      * Position of next bit in the buffered byte.
  92.      */
  93.     private int _nextBitIndex;
  94.     /**
  95.      * Set to true when all bits have been read.
  96.      */
  97.     private boolean _endOfStream = false;
  98.  
  99.     /**
  100.      * Reads the next byte from the input stream into
  101.      * <code>_nextByte</code>.
  102.      *
  103.      * @throws IOException If there is an IOException reading from the stream.
  104.      */
  105.     private void readAhead() throws IOException {
  106.         if (_endOfStream) {
  107.             return;
  108.         }
  109.         _nextByte = _in.read();
  110.         if (_nextByte == -1) {
  111.             _endOfStream = true;
  112.             return;
  113.         }
  114.         _nextBitIndex = 7;
  115.     }
  116. }

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