itextpdf-master/xtra/src/main/java/com/itextpdf/text/pdf/util/PdfResourceCounter.java
/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2022 iText Group NV
 * Authors: Bruno Lowagie, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
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 */
package com.itextpdf.text.pdf.util;

import com.itextpdf.text.pdf.PRIndirectReference;
import com.itextpdf.text.pdf.PdfArray;
import com.itextpdf.text.pdf.PdfDictionary;
import com.itextpdf.text.pdf.PdfName;
import com.itextpdf.text.pdf.PdfObject;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

/**
 * This class can be used to count the number of bytes needed when copying
 * pages from an existing PDF into a newly created PDF.
 */
public class PdfResourceCounter {
    /** A map of the resources that are already taken into account */
    protected Map<Integer, PdfObject> resources;
    
    /**
     * Creates a PdfResourceCounter instance to be used to count the resources
     * needed for either a page (in this case pass a page dictionary) or the
     * trailer (root and info dictionary) of a PDF file.
     * @param object    the object we want to examine
     */
    public PdfResourceCounter(PdfObject object) {
        resources = new HashMap<Integer, PdfObject>();
        process(object);
    }
    
    /**
     * Processes an object. If the object is indirect, it is added to the
     * list of resources. If not, it is just processed.
     * @param object    the object to process
     */
    protected final void process(PdfObject object) {
        PRIndirectReference ref = object.getIndRef();
        if (ref == null || resources.put(ref.getNumber(), object) == null) {
            loopOver(object);
        }
    }
    
    /**
     * In case an object is an array, a dictionary or a stream,
     * we need to loop over the entries and process them one by one.
     * @param object    the object to examine
     */
    protected final void loopOver(PdfObject object) {
        switch (object.type()) {
            case PdfObject.ARRAY:
                PdfArray array = (PdfArray)object;
                for (int i = 0; i < array.size(); i++) {
                    process(array.getDirectObject(i));
                }
                break;
            case PdfObject.DICTIONARY:
            case PdfObject.STREAM:
                PdfDictionary dict = (PdfDictionary)object;
                if (dict.isPages()) break;
                for (PdfName name : dict.getKeys()) {
                    process(dict.getDirectObject(name));
                }
                break;
        }
    }
    
    /**
     * Returns a map with the resources.
     * @return the resources
     */
    public Map<Integer, PdfObject> getResources() {
        return resources;
    }
    
    /**
     * Returns the resources needed for the object that was used to create
     * this PdfResourceCounter. If you pass a Map with resources that were
     * already used by other objects, these objects will not be taken into
     * account.
     * @param res   the resources that can be excluded when counting the bytes
     * @return the number of bytes needed for an object
     * @throws java.io.IOException
     */
    public long getLength(Map<Integer, PdfObject> res) throws IOException {
        long length = 0;
        PdfObject object;
        for (int ref : resources.keySet()) {
            if (res != null && res.containsKey(ref)) {
                continue;
            }
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            object = resources.get(ref);
            object.toPdf(null, baos);
            length += baos.size();
        }
        return length;
    }
}
