SVGImageReaderSpi.java
/*
* 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 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.plugins.svg;
import com.twelvemonkeys.imageio.spi.ImageReaderSpiBase;
import com.twelvemonkeys.lang.SystemUtil;
import javax.imageio.ImageReader;
import javax.imageio.spi.ServiceRegistry;
import javax.imageio.stream.ImageInputStream;
import java.io.ByteArrayOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.util.Locale;
import java.util.function.Predicate;
import static com.twelvemonkeys.imageio.util.IIOUtil.deregisterProvider;
/**
* SVGImageReaderSpi
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @version $Id: SVGImageReaderSpi.java,v 1.1 2003/12/02 16:45:00 haku Exp $
*/
public final class SVGImageReaderSpi extends ImageReaderSpiBase {
final static boolean SVG_READER_AVAILABLE = SystemUtil.isClassAvailable("com.twelvemonkeys.imageio.plugins.svg.SVGImageReader", SVGImageReaderSpi.class);
/**
* Creates an {@code SVGImageReaderSpi}.
*/
@SuppressWarnings("WeakerAccess")
public SVGImageReaderSpi() {
super(new SVGProviderInfo());
}
public boolean canDecodeInput(final Object source) throws IOException {
return source instanceof ImageInputStream && canDecode((ImageInputStream) source);
}
@SuppressWarnings("StatementWithEmptyBody")
private static boolean canDecode(final ImageInputStream input) throws IOException {
// NOTE: This test is quite quick as it does not involve any parsing,
// however it may not recognize all kinds of SVG documents.
try {
input.mark();
// TODO: This is not ok for UTF-16 and other wide encodings
// TODO: Use an XML (encoding) aware Reader instance instead
// Need to figure out pretty fast if this is XML or not
int b;
while (Character.isWhitespace((char) (b = input.read()))) {
// Skip over leading WS
}
// If it's not a tag, this can't be valid XML
if (b != '<') {
return false;
}
// Algorithm for detecting SVG:
// - Skip until begin tag '<' and read 4 bytes
// - if next is "?" skip until "?>" and start over
// - else if next is "!--" skip until "-->" and start over
// - else if next is "!DOCTYPE " skip any whitespace
// - compare next 3 bytes against "svg", return result
// - else
// - compare next 3 bytes against "svg", return result
byte[] buffer = new byte[4];
while (true) {
input.readFully(buffer);
if (buffer[0] == '?') {
// This is the XML declaration or a processing instruction
while (!((input.readByte() & 0xFF) == '?' && input.read() == '>')) {
// Skip until end of XML declaration or processing instruction or EOF
}
}
else if (buffer[0] == '!') {
if (buffer[1] == '-' && buffer[2] == '-') {
// This is a comment
while (!((input.readByte() & 0xFF) == '-' && input.read() == '-' && input.read() == '>')) {
// Skip until end of comment or EOF
}
}
else if (buffer[1] == 'D' && buffer[2] == 'O' && buffer[3] == 'C'
&& input.read() == 'T' && input.read() == 'Y'
&& input.read() == 'P' && input.read() == 'E') {
// This is the DOCTYPE declaration
while (Character.isWhitespace((char) (b = input.read()))) {
// Skip over WS
}
if (b == 's' && input.read() == 'v' && input.read() == 'g') {
// It's SVG, identified by DOCTYPE
return true;
}
// DOCTYPE found, but not SVG
return false;
}
// Something else, we'll skip
}
else {
// This is a normal tag
if (buffer[0] == 's' && buffer[1] == 'v' && buffer[2] == 'g'
&& (Character.isWhitespace((char) buffer[3]) || buffer[3] == ':')) {
// It's SVG, identified by root tag
return true;
}
// Read the full tag name (may contain a prefix of any length)
final int MAX_TAG_NAME = 256;
ByteArrayOutputStream nameBuf = new ByteArrayOutputStream(MAX_TAG_NAME);
// We already have 4 bytes in 'buffer' (from input.readFully(buffer))
int consumedFromBuffer = 0;
for (; consumedFromBuffer < buffer.length; consumedFromBuffer++) {
byte bb = buffer[consumedFromBuffer];
if (bb == '>' || Character.isWhitespace((char) bb) || bb == '/') {
break;
}
nameBuf.write(bb);
}
// If tag name not terminated yet, keep reading bytes (within limit)
final boolean incompleteTagName = consumedFromBuffer == buffer.length;
readBuffer(input, nameBuf, output -> incompleteTagName && output.size() < MAX_TAG_NAME,
bb -> bb == '>' || Character.isWhitespace(bb) || bb == '/');
final String name = nameBuf.toString("US-ASCII");
if (name.toLowerCase(Locale.ENGLISH).endsWith(":svg")) {
// Scan the rest of the tag attributes until '>' to find the SVG namespace URI
ByteArrayOutputStream attrBuf = new ByteArrayOutputStream();
final int MAX_ATTR_SCAN = 1024; // safe upper bound to keep it fast
readBuffer(input, attrBuf, output -> output.size() < MAX_ATTR_SCAN, bb -> bb == '>');
// If the tag contains the SVG namespace, it's SVG.
if (attrBuf.toString("US-ASCII").matches(
".*xmlns:" + name.split(":")[0] + "\\s*=\\s*\"http://www.w3.org/2000/svg\".*")) {
return true;
}
}
// If the tag is not "svg", this isn't SVG
return false;
}
while ((input.readByte() & 0xFF) != '<') {
// Skip over, until next begin tag or EOF
}
}
}
catch (EOFException ignore) {
// Possible for small files...
return false;
}
finally {
//noinspection ThrowFromFinallyBlock
input.reset();
}
}
private static void readBuffer(final ImageInputStream input, final ByteArrayOutputStream buffer,
final Predicate<ByteArrayOutputStream> loopCondition, Predicate<Byte> breakCondition) throws IOException {
while (loopCondition.test(buffer)) {
byte bb = input.readByte();
if (breakCondition.test(bb)) {
break;
}
buffer.write(bb);
}
}
public ImageReader createReaderInstance(final Object extension) throws IOException {
return new SVGImageReader(this);
}
public String getDescription(final Locale locale) {
return "Scalable Vector Graphics (SVG) format image reader";
}
@SuppressWarnings({"deprecation"})
@Override
public void onRegistration(final ServiceRegistry registry, final Class<?> category) {
// TODO: Perhaps just try to create an instance, and de-register if we fail?
if (!SVG_READER_AVAILABLE) {
System.err.println("Could not instantiate SVGImageReader (missing support classes).");
try {
// NOTE: This will break, but it gives us some useful debug info
new SVGImageReader(this);
}
catch (Throwable t) {
t.printStackTrace();
}
deregisterProvider(registry, this, category);
}
}
}