XMPScanner.java
/*
* Copyright (c) 2009, 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 of the copyright holder 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 HOLDER 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.imageio.metadata.xmp;
import com.twelvemonkeys.imageio.util.IIOUtil;
import javax.imageio.ImageIO;
import javax.imageio.stream.ImageInputStream;
import java.io.*;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
/**
* XMPScanner
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haraldk$
* @version $Id: XMPScanner.java,v 1.0 Nov 11, 2009 4:49:00 PM haraldk Exp$
*/
public final class XMPScanner {
/**
* {@code <?xpacket begin=}
* <p>
* <ul>
* <li>
* 8-bit (UTF-8):
* 0x3C 0x3F 0x78 0x70 0x61 0x63 0x6B 0x65 0x74 0x20
* 0x62 0x65 0x67 0x69 0x6E 0x3D
* </li>
* <li>16-bit encoding (UCS-2, UTF-16): (either big- or little-endian order)
* 0x3C 0x00 0x3F 0x00 0x78 0x00 0x70 0x00 0x61 0x00
* 0x63 0x00 0x6B 0x00 0x65 0x00 0x74 0x00 0x20 0x00 0x62 0x00
* 0x65 0x00 0x67 0x00 0x69 0x00 0x6E 0x00 0x3D [0x00]
* </li>
* <li>32-bit encoding (UCS-4):
* As 16 bit UCS2, with three 0x00 instead of one.</li>
* </ul>
* </p>
*/
private static final byte[] XMP_PACKET_BEGIN = {
0x3C, 0x3F, 0x78, 0x70, 0x61, 0x63, 0x6B, 0x65, 0x74, 0x20,
0x62, 0x65, 0x67, 0x69, 0x6E, 0x3D
};
/**
* {@code <?xpacket end=}
*/
private static final byte[] XMP_PACKET_END = {
0x3C, 0x3F, 0x78, 0x70, 0x61, 0x63, 0x6B, 0x65, 0x74, 0x20,
0x65, 0x6E, 0x64, 0x3D
};
/**
* Scans the given input for an XML metadata packet.
* The scanning process involves reading every byte in the file, while searching for an XMP packet.
* This process is very inefficient, compared to reading a known file format.
* <p>
* <em>NOTE: The XMP Specification says this method of reading an XMP packet
* should be considered a last resort.</em>
* <br>
* This is because files may contain multiple XMP packets, some which may be related to embedded resources,
* some which may be obsolete (or even incomplete).
* </p>
*
* @param pInput the input to scan. The input may be an {@link javax.imageio.stream.ImageInputStream} or
* any object that can be passed to {@link ImageIO#createImageInputStream(Object)}.
* Typically this may be a {@link File}, {@link InputStream} or {@link java.io.RandomAccessFile}.
*
* @return a character Reader
*
* @throws java.nio.charset.UnsupportedCharsetException if the encoding specified within the BOM is not supported
* by the JRE.
* @throws IOException if an I/O exception occurs reading from {@code pInput}.
* @see ImageIO#createImageInputStream(Object)
*/
@SuppressWarnings("StatementWithEmptyBody")
static public Reader scanForXMPPacket(final Object pInput) throws IOException {
ImageInputStream stream = pInput instanceof ImageInputStream ? (ImageInputStream) pInput : ImageIO.createImageInputStream(pInput);
// TODO: Might be more than one XMP block per file (it's possible to re-start for now)..
long pos;
pos = scanForSequence(stream, XMP_PACKET_BEGIN);
if (pos >= 0) {
// Skip ' OR " (plus possible nulls for 16/32 bit)
byte quote = stream.readByte();
if (quote == '\'' || quote == '"') {
Charset cs = null;
// Read BOM
byte[] bom = new byte[4];
stream.readFully(bom);
// NOTE: Empty string should be treated as UTF-8 for backwards compatibility
if (bom[0] == (byte) 0xEF && bom[1] == (byte) 0xBB && bom[2] == (byte) 0xBF && bom[3] == quote ||
bom[0] == quote) {
// UTF-8
cs = StandardCharsets.UTF_8;
}
else if (bom[0] == (byte) 0xFE && bom[1] == (byte) 0xFF && bom[2] == 0x00 && bom[3] == quote) {
// UTF-16 BIG endian
cs = StandardCharsets.UTF_16BE;
}
else if (bom[0] == 0x00 && bom[1] == (byte) 0xFF && bom[2] == (byte) 0xFE && bom[3] == quote) {
stream.skipBytes(1); // Alignment
// UTF-16 little endian
cs = StandardCharsets.UTF_16LE;
}
else if (bom[0] == 0x00 && bom[1] == 0x00 && bom[2] == (byte) 0xFE && bom[3] == (byte) 0xFF) {
// NOTE: 32-bit character set not supported by default
// UTF 32 BIG endian
cs = Charset.forName("UTF-32BE");
}
else if (bom[0] == 0x00 && bom[1] == 0x00 && bom[2] == 0x00 && bom[3] == (byte) 0xFF && stream.read() == 0xFE) {
stream.skipBytes(2); // Alignment
// NOTE: 32-bit character set not supported by default
// UTF 32 little endian
cs = Charset.forName("UTF-32LE");
}
if (cs != null) {
// Read all bytes until <?xpacket end= up-front or filter stream
stream.mark();
long end = scanForSequence(stream, XMP_PACKET_END);
stream.reset();
long length = end - stream.getStreamPosition();
Reader reader = new InputStreamReader(IIOUtil.createStreamAdapter(stream, length), cs);
// Skip until ?>
while (reader.read() != '>') {
}
// Return reader?
// How to decide between w or r?!
return reader;
}
}
}
return null;
}
/**
* Scans for a given ASCII sequence.
*
* @param pStream the stream to scan
* @param pSequence the byte sequence to search for
*
* @return the start position of the given sequence.
*
* @throws IOException if an I/O exception occurs during scanning
*/
private static long scanForSequence(final ImageInputStream pStream, final byte[] pSequence) throws IOException {
long start = -1L;
int index = 0;
int nullBytes = 0;
for (int read; (read = pStream.read()) >= 0;) {
if (pSequence[index] == (byte) read) {
// If this is the first byte in the sequence, store position
if (start == -1) {
start = pStream.getStreamPosition() - 1;
}
// Inside the sequence, there might be 1 or 3 null bytes, depending on 16/32 byte encoding
if (nullBytes == 1 || nullBytes == 3) {
pStream.skipBytes(nullBytes);
}
index++;
// If we found the entire sequence, we're done, return start position
if (index == pSequence.length) {
return start;
}
}
else if (index == 1 && read == 0 && nullBytes < 3) {
// Skip 1 or 3 null bytes for 16/32 bit encoding
nullBytes++;
}
else if (index != 0) {
// Start over
index = 0;
start = -1;
nullBytes = 0;
}
}
return -1L;
}
public static void main(final String[] pArgs) throws IOException {
ImageInputStream stream = ImageIO.createImageInputStream(new File(pArgs[0]));
Reader xmp;
while ((xmp = scanForXMPPacket(stream)) != null) {
BufferedReader reader = new BufferedReader(xmp);
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
}
stream.close();
}
}