# ObjectStreamXReference.java

    /*
     * 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.
     */
    package org.apache.pdfbox.pdfparser.xref;

    import org.apache.pdfbox.cos.COSBase;
    import org.apache.pdfbox.cos.COSObject;
    import org.apache.pdfbox.cos.COSObjectKey;
    import org.apache.pdfbox.pdfparser.PDFXRefStream;

    /**
     * A class representing a reference to an object stream entry in a PDF's crossreference stream ({@link PDFXRefStream}).
     *
     * @author Christian Appl
     */
    public class ObjectStreamXReference extends AbstractXReference
    {

        private final int objectStreamIndex;
        private final COSObjectKey key;
        private final COSBase object;
        private final COSObjectKey parentKey;

        /**
         * Prepares a object stream entry reference for the given {@link COSObject} in a PDF's crossreference stream
         * ({@link PDFXRefStream}).
         *
         * @param objectStreamIndex The index of the {@link COSObject} in the containing object stream.
         * @param key The {@link COSObjectKey}, that is represented by this entry.
         * @param object The {@link COSObject}, that is represented by this entry.
         * @param parentKey The {@link COSObjectKey} of the object stream, that is containing the object.
         */
        public ObjectStreamXReference(int objectStreamIndex, COSObjectKey key, COSBase object,
                COSObjectKey parentKey)
        {
            super(XReferenceType.OBJECT_STREAM_ENTRY);
            this.objectStreamIndex = objectStreamIndex;
            this.key = key;
            this.object = object;
            this.parentKey = parentKey;
        }

        /**
         * Returns the index of the {@link COSObject} in it's containing object stream.
         *
         * @return The index of the {@link COSObject} in it's containing object stream.
         */
        public int getObjectStreamIndex()
        {
            return objectStreamIndex;
        }

        /**
         * Returns the {@link COSObjectKey} of the object, that is described by this crossreference stream entry.
         *
         * @return The {@link COSObjectKey} of the object, that is described by this crossreference stream entry.
         */
        @Override
        public COSObjectKey getReferencedKey()
        {
            return key;
        }

        /**
         * Returns the {@link COSObject}, that is described by this crossreference stream entry.
         *
         * @return The {@link COSObject}, that is described by this crossreference stream entry.
         */
        public COSBase getObject()
        {
            return object;
        }

        /**
         * Returns the {@link COSObjectKey} of the object stream, that is containing the object.
         *
         * @return The {@link COSObjectKey} of the object stream, that is containing the object.
         */
        public COSObjectKey getParentKey()
        {
            return parentKey;
        }

        /**
         * Returns the value for the second column of the crossreference stream entry. (This is object number from the
         * {@link COSObjectKey} of the object stream, that is containing the object represented by this entry - for entries
         * of this type..)
         *
         * @return The value for the second column of the crossreference stream entry.
         */
        @Override
        public long getSecondColumnValue()
        {
            return getParentKey().getNumber();
        }

        /**
         * Returns the value for the third column of the crossreference stream entry. (This is index of the
         * {@link COSObject} in the containing object stream - for entries of this type.)
         *
         * @return The value for the third column of the crossreference stream entry.
         */
        @Override
        public long getThirdColumnValue()
        {
            return getObjectStreamIndex();
        }

        /**
         * Returns a string representation of this crossreference stream entry.
         *
         * @return A string representation of this crossreference stream entry.
         */
        @Override
        public String toString()
        {
            return "ObjectStreamEntry{" + " key=" + key + ", type=" + getType().getNumericValue()
                    + ", objectStreamIndex=" + objectStreamIndex + ", parent=" + parentKey + " }";
        }
    }