de.intarsys.pdf.cos.COSObjectProxy Maven / Gradle / Ivy
/*
* Copyright (c) 2007, intarsys consulting GmbH
*
* 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 intarsys 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
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
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package de.intarsys.pdf.cos;
import java.io.IOException;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import de.intarsys.pdf.writer.COSWriter;
import de.intarsys.tools.collection.EmptyIterator;
import de.intarsys.tools.randomaccess.IRandomAccess;
/**
* A "proxy object" used to intercept the visitor callback from the serializer.
*
* You can use this for example to implement an elegant solution for PDF
* signing, which is defined on the serialized bytes, except some defined byte
* range. The proxy mechanics allow for creating a placeholder for the signature
* data, filled in at the correct position later by some post processing.
*
*/
abstract public class COSObjectProxy extends COSCompositeObject implements
Cloneable {
/** The position when the signal from the serializer was detected */
private long position = -1;
private int length;
private COSObject object;
/**
* Create a {@link COSObjectProxy}
*/
public COSObjectProxy() {
//
}
@Override
public Object accept(ICOSObjectVisitor visitor) throws COSVisitorException {
if (object != null) {
return object.accept(visitor);
}
if (visitor instanceof ICOSProxyVisitor) {
return ((ICOSProxyVisitor) visitor).visitFromProxy(this);
}
return null;
}
@Override
public Iterator basicIterator() {
if (object == null) {
return EmptyIterator.UNIQUE;
}
return object.basicIterator();
}
@Override
protected String basicToString() {
if (object == null) {
return "COSObjectProxy: empty"; //$NON-NLS-1$
}
return object.stringValue();
}
@Override
protected Object clone() {
try {
return super.clone();
} catch (CloneNotSupportedException e) {
return null;
}
}
@Override
protected COSObject copyBasic() {
COSObjectProxy proxy = (COSObjectProxy) clone();
proxy.reserveData(getLength());
return proxy;
}
@Override
public COSObject copyDeep(Map copied) {
if (object != null) {
return object.copyDeep(copied);
}
return super.copyDeep(copied);
}
@Override
public COSObject copyShallow() {
if (object != null) {
return object.copyShallow();
}
return super.copyShallow();
}
/**
* The wrapped {@link COSObject}, according to COS level semantics. This
* method returns never null.
*
* @return The wrapped {@link COSObject}, according to COS level semantics.
*/
public COSObject cosGetObject() {
return object == null ? COSNull.NULL : object;
}
/**
* Realize the represented object.
*
* @param randomAccessData
* @return the represented object
* @throws IOException
*/
abstract protected COSObject createCOSObject(IRandomAccess randomAccessData)
throws IOException;
@Override
public COSObject dereference() {
return (object == null) ? this : object;
}
/**
* Attention: The user must handle encryption by himself. The COSWriter
* doesn't handle encryption in this state.
*
* @param writer
* @throws IOException
*/
public void ended(COSWriter writer) throws IOException {
if (object != null) {
// already done
return;
}
IOException createObjException = null;
IRandomAccess data = writer.getRandomAccess();
data.mark();
try {
try {
object = createCOSObject(data);
} catch (IOException e) {
createObjException = e;
}
data.seek(getPosition());
if (object != null) {
writer.writeObject(object);
} else {
writer.writeObject(COSNull.create());
}
long endPosition = getPosition() + getLength();
if (data.getOffset() < endPosition) {
long dif = endPosition - data.getOffset();
byte[] padding = new byte[(int) dif];
Arrays.fill(padding, (byte) ' ');
writer.write(padding);
} else if (data.getOffset() > endPosition) {
throw new IOException(
"Destroyed document, wrote more bytes than reserved!"); //$NON-NLS-1$
}
if (createObjException != null) {
throw createObjException;
}
} finally {
data.reset();
}
}
/**
* The length within the data stream for the serialization of this.
*
* @return The length within the data stream for the serialization of this.
*/
public int getLength() {
return length;
}
/**
* The object represented by the proxy.
*
* @return The object represented by the proxy.
*/
public COSObject getObject() {
return object;
}
/**
* The position within the data stream for the serialization of this.
*
* @return The position within the data stream for the serialization of
* this.
*/
public long getPosition() {
return position;
}
@Override
public Iterator iterator() {
if (object == null) {
return EmptyIterator.UNIQUE;
}
return object.iterator();
}
@Override
public boolean mayBeSwapped() {
return false;
}
/**
* Reserve length bytes for the serialization of this.
*
* @param pLength
* Number of bytes to be reserved.
*/
public void reserveData(int pLength) {
this.length = pLength;
}
public Object saveState() {
return null;
}
protected void setObject(COSObject object) {
this.object = object;
}
/**
* Assign the position within the data stream.
*
* @param position
* The position within the data stream.
*/
public void setPosition(long position) {
this.position = position;
}
}