001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.imaging.common.mylzw;
018
019import java.io.IOException;
020import java.io.OutputStream;
021import java.nio.ByteOrder;
022
023public class MyBitOutputStream extends OutputStream {
024    private final OutputStream os;
025    private final ByteOrder byteOrder;
026    private int bitsInCache;
027    private int bitCache;
028    private int bytesWritten;
029
030    public MyBitOutputStream(final OutputStream os, final ByteOrder byteOrder) {
031        this.byteOrder = byteOrder;
032        this.os = os;
033    }
034
035    @Override
036    public void write(final int value) throws IOException {
037        writeBits(value, 8);
038    }
039
040    // TODO: in and out streams CANNOT accurately read/write 32bits at a time,
041    // as int will overflow. should have used a long
042    public void writeBits(int value, final int sampleBits) throws IOException {
043        final int sampleMask = (1 << sampleBits) - 1;
044        value &= sampleMask;
045
046        if (byteOrder == ByteOrder.BIG_ENDIAN) {
047            // MSB, so add to right
048            bitCache = (bitCache << sampleBits) | value;
049        } else {
050            // LSB, so add to left
051            bitCache = bitCache | (value << bitsInCache);
052        }
053        bitsInCache += sampleBits;
054
055        while (bitsInCache >= 8) {
056            if (byteOrder == ByteOrder.BIG_ENDIAN) {
057                // MSB, so write from left
058                final int b = 0xff & (bitCache >> (bitsInCache - 8));
059                actualWrite(b);
060
061                bitsInCache -= 8;
062            } else {
063                // LSB, so write from right
064                final int b = 0xff & bitCache;
065                actualWrite(b);
066
067                bitCache >>= 8;
068                bitsInCache -= 8;
069            }
070            final int remainderMask = (1 << bitsInCache) - 1; // unnecessary
071            bitCache &= remainderMask; // unnecessary
072        }
073
074    }
075
076    private void actualWrite(final int value) throws IOException {
077        os.write(value);
078        bytesWritten++;
079    }
080
081    public void flushCache() throws IOException {
082        if (bitsInCache > 0) {
083            final int bitMask = (1 << bitsInCache) - 1;
084            int b = bitMask & bitCache;
085
086            if (byteOrder == ByteOrder.BIG_ENDIAN) {
087                // MSB, so write from left
088                b <<= 8 - bitsInCache; // left align fragment.
089                os.write(b);
090            } else {
091                // LSB, so write from right
092                os.write(b);
093            }
094        }
095
096        bitsInCache = 0;
097        bitCache = 0;
098    }
099
100    public int getBytesWritten() {
101        return bytesWritten + ((bitsInCache > 0) ? 1 : 0);
102    }
103
104}