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.mylzw; 018 019import java.io.FilterInputStream; 020import java.io.IOException; 021import java.io.InputStream; 022import java.nio.ByteOrder; 023 024public class MyBitInputStream extends FilterInputStream { 025 private final ByteOrder byteOrder; 026 private final boolean tiffLZWMode; 027 private long bytesRead; 028 private int bitsInCache; 029 private int bitCache; 030 031 public MyBitInputStream(final InputStream is, final ByteOrder byteOrder, final boolean tiffLZWMode) { 032 super(is); 033 this.byteOrder = byteOrder; 034 this.tiffLZWMode = tiffLZWMode; 035 } 036 037 public void flushCache() { 038 bitsInCache = 0; 039 bitCache = 0; 040 } 041 042 public long getBytesRead() { 043 return bytesRead; 044 } 045 046 @Override 047 public int read() throws IOException { 048 return readBits(8); 049 } 050 051 public int readBits(final int sampleBits) throws IOException { 052 while (bitsInCache < sampleBits) { 053 final int next = in.read(); 054 055 if (next < 0) { 056 if (tiffLZWMode) { 057 // pernicious special case! 058 return 257; 059 } 060 return -1; 061 } 062 063 final int newByte = 0xff & next; 064 065 if (byteOrder == ByteOrder.BIG_ENDIAN) { 066 bitCache = bitCache << 8 | newByte; 067 } else { 068 bitCache = newByte << bitsInCache | bitCache; 069 } 070 071 bytesRead++; 072 bitsInCache += 8; 073 } 074 final int sampleMask = (1 << sampleBits) - 1; 075 076 int sample; 077 078 if (byteOrder == ByteOrder.BIG_ENDIAN) { 079 sample = sampleMask & bitCache >> bitsInCache - sampleBits; 080 } else { 081 sample = sampleMask & bitCache; 082 bitCache >>= sampleBits; 083 } 084 085 final int result = sample; 086 087 bitsInCache -= sampleBits; 088 final int remainderMask = (1 << bitsInCache) - 1; 089 bitCache &= remainderMask; 090 091 return result; 092 } 093 094}