org.apache.commons.imaging.formats.tiff.datareaders.BitInputStream Maven / Gradle / Ivy
/*
* 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.datareaders;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteOrder;
/**
* Input stream reading 1-8, 16, 24 or 32 bits, starting from the most
* significant bit, but incapable of reading non-aligned and
* < 8 bit fields across byte boundaries.
*/
class BitInputStream extends InputStream {
private final InputStream is;
private final ByteOrder byteOrder;
private int cache;
private int cacheBitsRemaining;
private long bytesRead;
public BitInputStream(final InputStream is, final ByteOrder byteOrder) {
this.is = is;
this.byteOrder = byteOrder;
}
@Override
public int read() throws IOException {
if (cacheBitsRemaining > 0) {
throw new IOException("BitInputStream: incomplete bit read");
}
return is.read();
}
public final int readBits(final int count) throws IOException {
if (count < 8) {
if (cacheBitsRemaining == 0) {
// fill cache
cache = is.read();
cacheBitsRemaining = 8;
bytesRead++;
}
if (count > cacheBitsRemaining) {
throw new IOException(
"BitInputStream: can't read bit fields across bytes");
}
// int bits_to_shift = cache_bits_remaining - count;
cacheBitsRemaining -= count;
final int bits = cache >> cacheBitsRemaining;
switch (count) {
case 1:
return bits & 1;
case 2:
return bits & 3;
case 3:
return bits & 7;
case 4:
return bits & 15;
case 5:
return bits & 31;
case 6:
return bits & 63;
case 7:
return bits & 127;
}
}
if (cacheBitsRemaining > 0) {
throw new IOException("BitInputStream: incomplete bit read");
}
if (count == 8) {
bytesRead++;
return is.read();
}
/**
* Taking default order of the Tiff to be Little Endian and reversing
* the bytes in the end if its Big Endian.This is done because majority
* (may be all) of the files will be of Little Endian.
*/
if (byteOrder == ByteOrder.BIG_ENDIAN) {
if (count == 16) {
bytesRead += 2;
return (is.read() << 8) | (is.read() << 0);
}
if (count == 24) {
bytesRead += 3;
return (is.read() << 16) | (is.read() << 8) | (is.read() << 0);
}
if (count == 32) {
bytesRead += 4;
return (is.read() << 24) | (is.read() << 16) | (is.read() << 8)
| (is.read() << 0);
}
} else {
if (count == 16) {
bytesRead += 2;
return ((is.read() << 0) | (is.read() << 8));
}
if (count == 24) {
bytesRead += 3;
return ((is.read() << 0) | (is.read() << 8) | (is.read() << 16));
}
if (count == 32) {
bytesRead += 4;
return ((is.read() << 0) | (is.read() << 8) | (is.read() << 16) | (is
.read() << 24));
}
}
throw new IOException("BitInputStream: unknown error");
}
public void flushCache() {
cacheBitsRemaining = 0;
}
public long getBytesRead() {
return bytesRead;
}
}