/*
Copyright 2001,2003 The Apache Software Foundation
Licensed 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.batik.ext.awt.image.spi;
import java.io.IOException;
import java.io.InputStream;
import java.io.StreamCorruptedException;
/**
* This Image tag registry entry is built around the notion of magic
* numbers. These are strings of bytes that are at a well known
* location in the input stream (often the start).
*
* This base class can handle the compatiblity check based on a list
* of Magic Numbers that correspond to your format (Some formats have
* multiple magic numbers associated with them).
*/
public abstract class MagicNumberRegistryEntry
extends AbstractRegistryEntry
implements StreamRegistryEntry {
public static final float PRIORITY = 1000;
/**
* Inner class that represents one magic number. Simply consists
* of an offset in bytes from the start of the file, and a byte
* array that must match.
*/
public static class MagicNumber {
int offset;
byte [] magicNumber;
byte [] buffer;
/**
* Constructor.
* @param offset the location of the magic number in file.
* @param magicNumber the sequence of bytes that must match.
*/
public MagicNumber(int offset, byte[]magicNumber) {
this.offset = offset;
this.magicNumber = (byte[])magicNumber.clone();
buffer = new byte[magicNumber.length];
}
/**
* Returns the maximum number of bytes that will be read for
* this magic number compairison.
*/
int getReadlimit() {
return offset+magicNumber.length;
}
/**
* Performs the check of is.
*/
boolean isMatch(InputStream is)
throws StreamCorruptedException {
int idx = 0;
is.mark(getReadlimit());
try {
// Skip to the offset location.
while (idx < offset) {
int rn = (int)is.skip(offset-idx);
if (rn == -1) return false;
idx += rn;
}
idx = 0;
while (idx < buffer.length) {
int rn = is.read(buffer, idx, buffer.length-idx);
if (rn == -1) return false;
idx += rn;
}
for (int i=0; i<magicNumber.length; i++) {
if (magicNumber[i] != buffer[i])
return false;
}
} catch (IOException ioe) {
return false;
} finally {
try {
// Make sure we always put back what we have read.
// If this throws an IOException then the current
// stream should be closed an reopend by the registry.
is.reset();
} catch (IOException ioe) {
throw new StreamCorruptedException(ioe.getMessage());
}
}
return true;
}
}
/** The list of magic numbers associated with this entry */
MagicNumber [] magicNumbers;
/**
* Constructor, simplifies construction of entry when only
* one extension and one magic number is required.
* @param name Format Name
* @param ext Standard extension
* @param offset Offset of magic number
* @param magicNumber byte array to match.
*/
public MagicNumberRegistryEntry(String name,
String ext,
String mimeType,
int offset, byte[]magicNumber) {
super(name, PRIORITY, ext, mimeType);
magicNumbers = new MagicNumber[1];
magicNumbers[0] = new MagicNumber(offset, magicNumber);
}
/**
* Constructor, simplifies construction of entry when only
* one extension is required.
* @param name Format Name
* @param ext Standard extension
* @param magicNumbers Array of magic numbers any of which can match.
*/
public MagicNumberRegistryEntry(String name,
String ext,
String mimeType,
MagicNumber [] magicNumbers) {
super(name, PRIORITY, ext, mimeType);
this.magicNumbers = magicNumbers;
}
/**
* Constructor, simplifies construction of entry when only
* one magic number is required.
* @param name Format Name
* @param exts Standard set of extensions
* @param offset Offset of magic number
* @param magicNumber byte array to match.
*/
public MagicNumberRegistryEntry(String name,
String [] exts,
String [] mimeTypes,
int offset, byte[]magicNumber) {
super(name, PRIORITY, exts, mimeTypes);
magicNumbers = new MagicNumber[1];
magicNumbers[0] = new MagicNumber(offset, magicNumber);
}
/**
* Constructor
* @param name Format Name
* @param exts Standard set of extensions
* @param magicNumbers array of magic numbers any of which can match.
*/
public MagicNumberRegistryEntry(String name,
String [] exts,
String [] mimeTypes,
MagicNumber [] magicNumbers) {
super(name, PRIORITY, exts, mimeTypes);
this.magicNumbers = magicNumbers;
}
/**
* Constructor, allows for overriding the default priority of
* magic number entries. This should be needed very rarely since
* magic number checks are fairly relyable and hence aren't usually
* sensative to order issues.
* @param name Format Name
* @param exts Standard set of extensions
* @param magicNumbers array of magic numbers any of which can match.
* @param priority The priority of this entry (1000 is baseline)
*/
public MagicNumberRegistryEntry(String name,
String [] exts,
String [] mimeTypes,
MagicNumber [] magicNumbers,
float priority) {
super(name, priority, exts, mimeTypes);
this.magicNumbers = magicNumbers;
}
/**
* Returns the maximume read ahead needed for all magic numbers.
*/
public int getReadlimit() {
int maxbuf = 0;
for (int i=0; i<magicNumbers.length; i++) {
int req = magicNumbers[i].getReadlimit();
if (req > maxbuf) maxbuf = req;
}
return maxbuf;
}
/**
* Check if the stream contains an image that can be
* handled by this format handler
*/
public boolean isCompatibleStream(InputStream is)
throws StreamCorruptedException {
for (int i=0; i<magicNumbers.length; i++) {
if (magicNumbers[i].isMatch(is))
return true;
}
return false;
}
}