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/*
 * 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.sanselan.common.mylzw;

import java.io.IOException;
import java.io.OutputStream;

import org.apache.sanselan.common.BinaryConstants;

public class MyBitOutputStream extends OutputStream implements BinaryConstants
{
	private final OutputStream os;
	private final int byteOrder;

	public MyBitOutputStream(OutputStream os, int byteOrder)
	{
		this.byteOrder = byteOrder;
		this.os = os;
	}

	public void write(int value) throws IOException
	{
		writeBits(value, 8);
	}

	private int bitsInCache = 0;
	private int bitCache = 0;

	// TODO: in and out streams CANNOT accurately read/write 32bits at a time,
	// as int will overflow.  should have used a long
	public void writeBits(int value, int SampleBits) throws IOException
	{
		int sampleMask = (1 << SampleBits) - 1;
		value &= sampleMask;

		if (byteOrder == BYTE_ORDER_NETWORK) // MSB, so add to right
		{
			bitCache = (bitCache << SampleBits) | value;
		}
		else if (byteOrder == BYTE_ORDER_INTEL) // LSB, so add to left
		{
			bitCache = bitCache | (value << bitsInCache);
		}
		else
			throw new IOException("Unknown byte order: " + byteOrder);
		bitsInCache += SampleBits;

		while (bitsInCache >= 8)
		{
			if (byteOrder == BYTE_ORDER_NETWORK) // MSB, so write from left
			{
				int b = 0xff & (bitCache >> (bitsInCache - 8));
				actualWrite(b);

				bitsInCache -= 8;
			}
			else if (byteOrder == BYTE_ORDER_INTEL) // LSB, so write from right
			{
				int b = 0xff & bitCache;
				actualWrite(b);

				bitCache >>= 8;
				bitsInCache -= 8;
			}
			int remainderMask = (1 << bitsInCache) - 1; // unneccesary
			bitCache &= remainderMask; // unneccesary
		}

	}

	private int bytesWritten = 0;

	private void actualWrite(int value) throws IOException
	{
		os.write(value);
		bytesWritten++;
	}

	public void flushCache() throws IOException
	{
		if (bitsInCache > 0)
		{
			int bitMask = (1 << bitsInCache) - 1;
			int b = bitMask & bitCache;

			if (byteOrder == BYTE_ORDER_NETWORK) // MSB, so write from left
			{
				b <<= 8 - bitsInCache; // left align fragment.
				os.write(b);
			}
			else if (byteOrder == BYTE_ORDER_INTEL) // LSB, so write from right
			{
				os.write(b);
			}
		}

		bitsInCache = 0;
		bitCache = 0;
	}

	public int getBytesWritten()
	{
		return bytesWritten + ((bitsInCache > 0) ? 1 : 0);
	}

}