de.intarsys.pdf.st.STXRefEntryFree Maven / Gradle / Ivy

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/*
 * 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
 * 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 de.intarsys.pdf.st;

import de.intarsys.pdf.cos.COSObject;
import de.intarsys.pdf.crypt.ISystemSecurityHandler;

/**
 * Represents a free object entry in a pdf xref table.
 * 
 */
public class STXRefEntryFree extends STXRefEntry {
	/** a link to the next free XRef entry */
	private STXRefEntryFree next = this;

	/** a link to the prev free XRef entry */
	private STXRefEntryFree prev = this;

	private int nextFreeObject;

	public STXRefEntryFree(int objectNumber, int generationNumber,
			int nextFreeObject) {
		super(objectNumber, generationNumber);
		this.nextFreeObject = nextFreeObject;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see de.intarsys.pdf.storage.STXRefEntry#accept(de.intarsys.pdf.storage.IXRefEntryVisitor)
	 */
	@Override
	public void accept(IXRefEntryVisitor visitor)
			throws XRefEntryVisitorException {
		visitor.visitFromFree(this);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see de.intarsys.pdf.storage.STXRefEntry#copy()
	 */
	@Override
	public STXRefEntry copy() {
		return new STXRefEntryFree(getObjectNumber(), getGenerationNumber(),
				getNextFreeObjectNumber());
	}

	/**
	 * Add a new free entry in the linked list of free entries. The linked list
	 * is formed by the head entry with index 0. This entry and all subsequent
	 * hold a reference to their successor and predecessor. Adding a new entry
	 * means that we look up the entry in the linked list, starting at the head,
	 * that has the highest index smaller than the index of the new entry. The
	 * new entry is inserted after that position in the linked list.
	 * 
	 * @param entry
	 *            The new entry to insert in the linked list.
	 */
	public void enqueue(STXRefEntryFree entry) {
		int prevIndex = getPrev().getObjectNumber();
		if ((prevIndex == 0) || (prevIndex < entry.getObjectNumber())) {
			entry.setNext(this);
			entry.setPrev(getPrev());
			getPrev().setNext(entry);
			this.setPrev(entry);
		} else {
			getPrev().enqueue(entry);
		}
	}

	@Override
	public STXRefEntryOccupied fill(int pos) {
		unlink();

		/*
		 * STXRefEntry newEntry = STXRefEntryOccupied.create( getObjectNumber(),
		 * pos, getGenerationNumber() ); return newEntry.fill(pos);
		 */
		return null;
	}

	@Override
	public long getColumn1() {
		return getNextFreeObjectNumber();
	}

	@Override
	public int getColumn2() {
		return getGenerationNumber();
	}

	protected STXRefEntryFree getNext() {
		return next;
	}

	public int getNextFreeObjectNumber() {
		return nextFreeObject;
	}

	protected STXRefEntryFree getPrev() {
		return prev;
	}

	@Override
	public boolean isFree() {
		return true;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see de.intarsys.pdf.storage.STXRefEntry#loadObject(de.intarsys.pdf.cos.COSIndirectObject)
	 */
	@Override
	public COSObject load(STDocument doc, ISystemSecurityHandler securityHandler) {
		return null;
	}

	private void setNext(STXRefEntryFree free) {
		next = free;
	}

	private void setPrev(STXRefEntryFree free) {
		prev = free;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see de.intarsys.pdf.writer.XRefEntry#unlink()
	 */
	@Override
	protected void unlink() {
		getPrev().setNext(getNext());
		getNext().setPrev(getPrev());
		setPrev(this);
		setNext(this);
	}
}