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.InputStream; 021import java.nio.ByteOrder; 022 023public class MyBitInputStream extends InputStream { 024 private final InputStream is; 025 private final ByteOrder byteOrder; 026 private boolean tiffLZWMode; 027 private long bytesRead; 028 private int bitsInCache; 029 private int bitCache; 030 031 public MyBitInputStream(final InputStream is, final ByteOrder byteOrder) { 032 this.byteOrder = byteOrder; 033 this.is = is; 034 } 035 036 @Override 037 public int read() throws IOException { 038 return readBits(8); 039 } 040 041 public void setTiffLZWMode() { 042 tiffLZWMode = true; 043 } 044 045 public int readBits(final int sampleBits) throws IOException { 046 while (bitsInCache < sampleBits) { 047 final int next = is.read(); 048 049 if (next < 0) { 050 if (tiffLZWMode) { 051 // pernicious special case! 052 return 257; 053 } 054 return -1; 055 } 056 057 final int newByte = (0xff & next); 058 059 if (byteOrder == ByteOrder.BIG_ENDIAN) { 060 bitCache = (bitCache << 8) | newByte; 061 } else { 062 bitCache = (newByte << bitsInCache) | bitCache; 063 } 064 065 bytesRead++; 066 bitsInCache += 8; 067 } 068 final int sampleMask = (1 << sampleBits) - 1; 069 070 int sample; 071 072 if (byteOrder == ByteOrder.BIG_ENDIAN) { 073 sample = sampleMask & (bitCache >> (bitsInCache - sampleBits)); 074 } else { 075 sample = sampleMask & bitCache; 076 bitCache >>= sampleBits; 077 } 078 079 final int result = sample; 080 081 bitsInCache -= sampleBits; 082 final int remainderMask = (1 << bitsInCache) - 1; 083 bitCache &= remainderMask; 084 085 return result; 086 } 087 088 public void flushCache() { 089 bitsInCache = 0; 090 bitCache = 0; 091 } 092 093 public long getBytesRead() { 094 return bytesRead; 095 } 096 097}