jwo.utils.gifutils
Class BitInputStream

java.lang.Object
  java.io.InputStream
      java.io.FilterInputStream
          jwo.utils.gifutils.BitInputStream

All Implemented Interfaces:

Closeable

Direct Known Subclasses:

GIFInputStream

public class BitInputStream
extends FilterInputStream

Allows the reading of 1 to 32 bits at a time, on any bit boundary. Bits are read from bytes, least significant bit first.

Version:

2.3, 22nd August, 1998, modified 11th April, 2006.

Author:

Benjamin E. Norman, Minor modificiations, Jo Wood.

Field Summary

protected long	cachedBits Stores any cached bits which have been read in from the underlying stream but not yet returned to the user
protected int	numCachedBits Number of valid bits in 'cachedBits'.

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

BitInputStream(InputStream is)
Creates a BitInputStream, assuming that at least 5 bytes are available on the underlying stream.

Method Summary

int	read() Reads a byte at the current bit boundary.
int	readBit() Reads the next bit from the underlying input stream.
int	readBits(int numBits) Reads the given number of bits (1 to 32) from the underlying input stream.

Methods inherited from class java.io.FilterInputStream

available, close, mark, markSupported, read, read, reset, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

cachedBits

protected long cachedBits

Stores any cached bits which have been read in from the underlying stream but not yet returned to the user

numCachedBits

protected int numCachedBits

Number of valid bits in 'cachedBits'. This should always be >= 32 for efficiency, unless EOF has been reached

Constructor Detail

BitInputStream

public BitInputStream(InputStream is)

Creates a BitInputStream, assuming that at least 5 bytes are available on the underlying stream.

Parameters:

is - Underlying input stream upon which to base this one.

Method Detail

read

public int read()
         throws IOException

Reads a byte at the current bit boundary.

Overrides:

read in class FilterInputStream

Returns:

The byte that has been read or -1 if 8 bits are not available before EOF is reached.

Throws:

IOException - If problem reading from input stream.

readBits

public int readBits(int numBits)
             throws EOFException,
                    IllegalArgumentException,
                    IOException

Reads the given number of bits (1 to 32) from the underlying input stream.

Parameters:

numBits - Number of bits to read.

Returns:

Data read from input stream.

Throws:

EOFException - if the given number of bits are not available before EOF.

IllegalArgumentException - if numBits is not between 1 and 32.

IOException - if problem reading bits from input stream.

readBit

public int readBit()
            throws IOException

Reads the next bit from the underlying input stream.

Returns:

The read data or -1 on EOF.

Throws:

IOException - if problem reading bits from input stream.