BitInputStreamFlexible.java
/*
* 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.commons.imaging.formats.tiff.itu_t4;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.commons.imaging.ImagingException;
/**
* Input stream that allows reading up to 32 bits across byte boundaries in most significant bit first order.
*/
final class BitInputStreamFlexible extends FilterInputStream {
// TODO should be byte order conscious, that is, TIFF for reading
// samples size < 8 - shouldn't that effect their order within byte?
private int cache;
private int cacheBitsRemaining;
private long bytesRead;
BitInputStreamFlexible(final InputStream is) {
super(is);
}
public void flushCache() {
cacheBitsRemaining = 0;
}
public long getBytesRead() {
return bytesRead;
}
@Override
public int read() throws IOException {
if (cacheBitsRemaining > 0) {
throw new ImagingException("BitInputStream: incomplete bit read");
}
return in.read();
}
public int readBits(int count) throws IOException {
if (count <= 32) {
// catch-all
int result = 0;
// int done = 0;
if (cacheBitsRemaining > 0) {
if (count >= cacheBitsRemaining) {
result = (1 << cacheBitsRemaining) - 1 & cache;
count -= cacheBitsRemaining;
cacheBitsRemaining = 0;
} else {
// cache >>= count;
cacheBitsRemaining -= count;
result = (1 << count) - 1 & cache >> cacheBitsRemaining;
count = 0;
}
}
while (count >= 8) {
cache = in.read();
if (cache < 0) {
throw new ImagingException("Couldn't read bits");
}
// System.out.println("cache 1: " + cache + " ("
// + Integer.toHexString(cache) + ", "
// + Integer.toBinaryString(cache) + ")");
bytesRead++;
result = result << 8 | 0xff & cache;
count -= 8;
}
if (count > 0) {
cache = in.read();
if (cache < 0) {
throw new ImagingException("Couldn't read bits");
}
// System.out.println("cache 2: " + cache + " ("
// + Integer.toHexString(cache) + ", "
// + Integer.toBinaryString(cache) + ")");
bytesRead++;
cacheBitsRemaining = 8 - count;
result = result << count | (1 << count) - 1 & cache >> cacheBitsRemaining;
count = 0;
}
return result;
}
throw new ImagingException("BitInputStream: unknown error");
}
}