com.twelvemonkeys.io.enc.PackBitsDecoder Maven / Gradle / Ivy
The newest version!
/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name "TwelveMonkeys" nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.twelvemonkeys.io.enc;
import java.io.IOException;
import java.io.InputStream;
import java.io.EOFException;
/**
* Decoder implementation for Apple PackBits run-length encoding.
*
* From Wikipedia, the free encyclopedia
* PackBits is a fast, simple compression scheme for run-length encoding of
* data.
*
* Apple introduced the PackBits format with the release of MacPaint on the
* Macintosh computer. This compression scheme is one of the types of
* compression that can be used in TIFF-files.
*
* A PackBits data stream consists of packets of one byte of header followed by
* data. The header is a signed byte; the data can be signed, unsigned, or
* packed (such as MacPaint pixels).
*
* Header byte Data 0 to 127 1 + n literal bytes of data 0 to -127 One byte of data, repeated 1 - n times in
* the decompressed output -128 No operation
*
* Note that interpreting 0 as positive or negative makes no difference in the
* output. Runs of two bytes adjacent to non-runs are typically written as
* literal data.
*
* See Understanding PackBits
*
* @author Harald Kuhr
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/io/enc/PackBitsDecoder.java#1 $
*/
public final class PackBitsDecoder implements Decoder {
private final boolean mDisableNoop;
private int mLeftOfRun;
private boolean mSplitRun;
private boolean mEOF;
/** Creates a {@code PackBitsDecoder}. */
public PackBitsDecoder() {
this(false);
}
/**
* Creates a {@code PackBitsDecoder}, with optional compatibility mode.
*
* As some implementations of PackBits-like encoders treat {@code -128} as length of
* a compressed run, instead of a no-op, it's possible to disable no-ops
* for compatibility.
* Should be used with caution, even though, most known encoders never write
* no-ops in the compressed streams.
*
* @param pDisableNoop {@code true} if {@code -128} should be treated as a compressed run, and not a no-op
*/
public PackBitsDecoder(final boolean pDisableNoop) {
mDisableNoop = pDisableNoop;
}
/**
* Decodes bytes from the given input stream, to the given buffer.
*
* @param pStream the stream to decode from
* @param pBuffer a byte array, minimum 128 (or 129 if no-op is disabled)
* bytes long
* @return The number of bytes decoded
*
* @throws IOException
*/
public int decode(final InputStream pStream, final byte[] pBuffer) throws IOException {
if (mEOF) {
return -1;
}
int read = 0;
final int max = pBuffer.length;
// TODO: Don't decode more than single runs, because some writers add pad bytes inside the stream...
while (read < max) {
int n;
if (mSplitRun) {
// Continue run
n = mLeftOfRun;
mSplitRun = false;
}
else {
// Start new run
int b = pStream.read();
if (b < 0) {
mEOF = true;
break;
}
n = (byte) b;
}
// Split run at or before max
if (n >= 0 && n + 1 + read > max) {
mLeftOfRun = n;
mSplitRun = true;
break;
}
else if (n < 0 && -n + 1 + read > max) {
mLeftOfRun = n;
mSplitRun = true;
break;
}
try {
if (n >= 0) {
// Copy next n + 1 bytes literally
readFully(pStream, pBuffer, read, n + 1);
read += n + 1;
}
// Allow -128 for compatibility, see above
else if (mDisableNoop || n != -128) {
// Replicate the next byte -n + 1 times
byte value = readByte(pStream);
for (int i = -n + 1; i > 0; i--) {
pBuffer[read++] = value;
}
}
// else NOOP (-128)
}
catch (IndexOutOfBoundsException e) {
throw new DecodeException("Error in PackBits decompression, data seems corrupt", e);
}
}
return read;
}
private static byte readByte(final InputStream pStream) throws IOException {
int read = pStream.read();
if (read < 0) {
throw new EOFException("Unexpected end of PackBits stream");
}
return (byte) read;
}
private static void readFully(final InputStream pStream, final byte[] pBuffer, final int pOffset, final int pLength) throws IOException {
if (pLength < 0) {
throw new IndexOutOfBoundsException();
}
int read = 0;
while (read < pLength) {
int count = pStream.read(pBuffer, pOffset + read, pLength - read);
if (count < 0) {
throw new EOFException("Unexpected end of PackBits stream");
}
read += count;
}
}
}