/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.pdfbox.io;
import java.io.InputStream;
import java.io.IOException;
/**
* This is an n-bit input stream. This means that you can read chunks of data
* as any number of bits, not just 8 bits like the regular input stream. Just set the
* number of bits that you would like to read on each call. The default is 8.
*
* @author <a href="mailto:ben@benlitchfield.com">Ben Litchfield</a>
* @version $Revision: 1.4 $
*/
public class NBitInputStream
{
private int bitsInChunk;
private InputStream in;
private int currentByte;
private int bitsLeftInCurrentByte;
/**
* Constructor.
*
* @param is The input stream to read from.
*/
public NBitInputStream( InputStream is )
{
in = is;
bitsLeftInCurrentByte = 0;
bitsInChunk = 8;
}
/**
* This will unread some data.
*
* @param data The data to put back into the stream.
*/
public void unread( long data )
{
data <<= bitsLeftInCurrentByte;
currentByte |= data;
bitsLeftInCurrentByte += bitsInChunk;
}
/**
* This will read the next n bits from the stream and return the unsigned
* value of those bits.
*
* @return The next n bits from the stream.
*
* @throws IOException If there is an error reading from the underlying stream.
*/
public long read() throws IOException
{
long retval = 0;
for( int i=0; i<bitsInChunk && retval != -1; i++ )
{
if( bitsLeftInCurrentByte == 0 )
{
currentByte = in.read();
bitsLeftInCurrentByte = 8;
}
if( currentByte == -1 )
{
retval = -1;
}
else
{
retval <<= 1;
retval |= ((currentByte >> (bitsLeftInCurrentByte-1))&0x1);
bitsLeftInCurrentByte--;
}
}
return retval;
}
/** Getter for property bitsToRead.
* @return Value of property bitsToRead.
*/
public int getBitsInChunk()
{
return bitsInChunk;
}
/** Setter for property bitsToRead.
* @param bitsInChunkValue New value of property bitsToRead.
*/
public void setBitsInChunk(int bitsInChunkValue)
{
bitsInChunk = bitsInChunkValue;
}
}