com.phloc.commons.io.streams.NonBlockingBitOutputStream Maven / Gradle / Ivy
/**
* Copyright (C) 2006-2015 phloc systems
* http://www.phloc.com
* office[at]phloc[dot]com
*
* Licensed 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 com.phloc.commons.io.streams;
import java.io.Closeable;
import java.io.Flushable;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteOrder;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.phloc.commons.CGlobal;
import com.phloc.commons.ValueEnforcer;
import com.phloc.commons.string.ToStringGenerator;
/**
* The {@link NonBlockingBitOutputStream} allows writing individual bits to a
* general Java OutputStream. Like the various Stream-classes from Java, the
* BitOutputStream has to be created based on another OutputStream. This class
* is able to write a single bit to a stream (even though a byte has to be
* filled until the data is flushed to the underlying output stream). It is also
* able to write an integer value to the stream using the specified number of
* bits.
* For a thread-safe version see {@link BitOutputStream}
*
* @author Andreas Jakl
* @author Philip Helger
*/
public class NonBlockingBitOutputStream implements Closeable, Flushable
{
private static final Logger s_aLogger = LoggerFactory.getLogger (NonBlockingBitOutputStream.class);
/**
* The Java OutputStream that is used to write completed bytes.
*/
private OutputStream m_aOS;
private final boolean m_bHighOrderBitFirst;
/**
* The temporary buffer containing the individual bits until a byte has been
* completed and can be committed to the output stream.
*/
private int m_nBuffer;
/**
* Counts how many bits have been cached up to now.
*/
private int m_nBufferedBitCount;
/**
* Create a new bit output stream based on an existing Java OutputStream.
*
* @param aOS
* the output stream this class should use. May not be
* null.
* @param aByteOrder
* The non-null byte order to use.
*/
public NonBlockingBitOutputStream (@Nonnull final OutputStream aOS, @Nonnull final ByteOrder aByteOrder)
{
ValueEnforcer.notNull (aOS, "OutputStream");
ValueEnforcer.notNull (aByteOrder, "ByteOrder");
m_aOS = aOS;
m_bHighOrderBitFirst = aByteOrder.equals (ByteOrder.LITTLE_ENDIAN);
m_nBufferedBitCount = 0;
}
/**
* @return The byte order used. Never null.
*/
@Nonnull
public ByteOrder getByteOrder ()
{
return m_bHighOrderBitFirst ? ByteOrder.LITTLE_ENDIAN : ByteOrder.BIG_ENDIAN;
}
/**
* Write a single bit to the stream. It will only be flushed to the underlying
* OutputStream when a byte has been completed or when flush() manually.
*
* @param aBit
* 1 if the bit should be set, 0 if not
* @throws IOException
* In case writing to the output stream failed
*/
public void writeBit (final int aBit) throws IOException
{
if (m_aOS == null)
throw new IllegalStateException ("Already closed");
if (aBit != CGlobal.BIT_NOT_SET && aBit != CGlobal.BIT_SET)
throw new IllegalArgumentException (aBit + " is not a bit");
if (aBit == CGlobal.BIT_SET)
if (m_bHighOrderBitFirst)
m_nBuffer |= (aBit << (7 - m_nBufferedBitCount));
else
m_nBuffer |= (aBit << m_nBufferedBitCount);
if (++m_nBufferedBitCount == CGlobal.BITS_PER_BYTE)
flush ();
}
/**
* Write the specified number of bits from the int value to the stream.
* Corresponding to the InputStream, the bits are written starting at the
* highest bit ( >> aNumberOfBits ), going down to the lowest bit ( >> 0 ).
*
* @param aValue
* the int containing the bits that should be written to the stream.
* @param nNumBits
* how many bits of the integer should be written to the stream.
* @throws IOException
* In case writing to the output stream failed
*/
public void writeBits (final int aValue, @Nonnegative final int nNumBits) throws IOException
{
ValueEnforcer.isBetweenInclusive (nNumBits, "NumberOfBits", 1, CGlobal.BITS_PER_INT);
for (int i = nNumBits - 1; i >= 0; i--)
writeBit ((aValue >> i) & 1);
}
/**
* Write the current cache to the stream and reset the buffer.
*
* @throws IOException
* In case writing to the output stream failed
*/
public void flush () throws IOException
{
if (m_nBufferedBitCount > 0)
{
if (m_nBufferedBitCount != CGlobal.BITS_PER_BYTE)
if (s_aLogger.isDebugEnabled ())
s_aLogger.debug ("Flushing BitOutputStream with only " + m_nBufferedBitCount + " bits");
m_aOS.write ((byte) m_nBuffer);
m_nBufferedBitCount = 0;
m_nBuffer = 0;
}
}
/**
* Flush the data and close the underlying output stream.
*/
public void close ()
{
StreamUtils.flush (this);
StreamUtils.close (m_aOS);
m_aOS = null;
}
@Override
public String toString ()
{
return new ToStringGenerator (this).append ("OS", m_aOS)
.append ("highOrderBitFirst", m_bHighOrderBitFirst)
.append ("buffer", m_nBuffer)
.append ("bitCount", m_nBufferedBitCount)
.toString ();
}
}