/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

/* $Id: PDFReference.java 1661887 2015-02-24 11:23:44Z ssteiner $ */

package org.apache.fop.pdf;

import java.io.OutputStream;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;

Class representing a PDF object reference. The object holds a soft reference to the actual
PDF object so the garbage collector can free the object if it's not referenced elsewhere. The
important thing about the class is the reference information to the actual PDF object in the
PDF file.
/**
 * Class representing a PDF object reference. The object holds a soft reference to the actual
 * PDF object so the garbage collector can free the object if it's not referenced elsewhere. The
 * important thing about the class is the reference information to the actual PDF object in the
 * PDF file.
 */
public class PDFReference implements PDFWritable {

    private PDFObjectNumber objectNumber;
    private int generation;

    private Reference<PDFObject> objReference;

    
Creates a new PDF reference.
Params:
obj – the object to be referenced/**
     * Creates a new PDF reference.
     * @param obj the object to be referenced
     */
    public PDFReference(PDFObject obj) {
        this.objectNumber = obj.getObjectNumber();
        this.generation = obj.getGeneration();
        this.objReference = new SoftReference<PDFObject>(obj);
    }

    
Creates a new PDF reference, but without a reference to the original object.
Params:
ref – an object reference/**
     * Creates a new PDF reference, but without a reference to the original object.
     * @param ref an object reference
     */
    public PDFReference(String ref) {
        if (ref == null) {
            throw new NullPointerException("ref must not be null");
        }
        String[] parts = ref.split(" ");
        assert parts.length == 3;
        this.objectNumber = new PDFObjectNumber(Integer.parseInt(parts[0]));
        this.generation = Integer.parseInt(parts[1]);
        assert "R".equals(parts[2]);
    }

    
Returns the PDF object
Returns:
the PDF object, or null if it has been released/**
     * Returns the PDF object
     * @return the PDF object, or null if it has been released
     */
    public PDFObject getObject() {
        if (this.objReference != null) {
            PDFObject obj = this.objReference.get();
            if (obj == null) {
                this.objReference = null;
            }
            return obj;
        } else {
            return null;
        }
    }

    
Returns the object number.
Returns:
the object number/**
     * Returns the object number.
     * @return the object number
     */
    public PDFObjectNumber getObjectNumber() {
        return this.objectNumber;
    }

    
Returns the generation.
Returns:
the generation/**
     * Returns the generation.
     * @return the generation
     */
    public int getGeneration() {
        return this.generation;
    }

    
{@inheritDoc} /** {@inheritDoc} */
    @Override
    public String toString() {
        StringBuilder textBuffer = new StringBuilder();
        outputInline(null, textBuffer);
        return textBuffer.toString();
    }

    
{@inheritDoc} /** {@inheritDoc} */
    public void outputInline(OutputStream out, StringBuilder textBuffer) {
        textBuffer.append(getObjectNumber().getNumber()).append(' ').append(getGeneration()).append(" R");
    }

}