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#region PDFsharp - A .NET library for processing PDF
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// Stefan Lange (mailto:Stefan.Lange@pdfsharp.com)
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// Copyright (c) 2005-2008 empira Software GmbH, Cologne (Germany)
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// http://www.pdfsharp.com
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// http://sourceforge.net/projects/pdfsharp
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// Permission is hereby granted, free of charge, to any person obtaining a
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// copy of this software and associated documentation files (the "Software"),
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// to deal in the Software without restriction, including without limitation
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// the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// and/or sell copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following conditions:
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// The above copyright notice and this permission notice shall be included
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// in all copies or substantial portions of the Software.
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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// With this define each iref object gets a unique number (uid) to make them distinguishable in the debugger
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using System.Diagnostics;
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using System.Collections;
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using PdfSharp.Internal;
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using PdfSharp.Pdf.IO;
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namespace PdfSharp.Pdf.Advanced
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/// Represents an indirect reference to a PdfObject.
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[DebuggerDisplay("iref({ObjectNumber}, {GenerationNumber})")]
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public sealed class PdfReference : PdfItem
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// * A PdfReference holds the either ObjectID or the PdfObject or both.
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// * Each PdfObject has a PdfReference if and only if it is an indirect object. Direct objects have
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// no PdfReference, because they are embedded in a parent objects.
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// * PdfReference objects are used to reference PdfObject instances. A value in a PDF dictionary
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// or array that is a PdfReference represents an indirect reference. A value in a PDF dictionary or
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// or array that is a PdfObject represents a direct (or embeddded) object.
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// * When a PDF file is imported, the PdfXRefTable is filled with PdfReference objects keeping the
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// ObjectsIDs and file positions (offsets) of all indirect objects.
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// * Indirect objects can easily be renumbered because they do not rely on their ObjectsIDs.
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// * During modification of a document the ObjectID of an indirect object has no meaning,
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// except that they must be different in pairs.
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/// Initializes a new PdfReference instance for the specified indirect object.
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public PdfReference(PdfObject pdfObject)
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Debug.Assert(pdfObject.Reference == null, "Must not create iref for an object that already has one.");
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this.value = pdfObject;
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#if UNIQUE_IREF && DEBUG
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this.uid = ++PdfReference.counter;
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/// Initializes a new PdfReference instance from the specified object identifier and file position.
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public PdfReference(PdfObjectID objectID, int position)
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this.objectID = objectID;
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this.position = position;
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#if UNIQUE_IREF && DEBUG
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this.uid = ++PdfReference.counter;
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/// Writes the object in PDF iref table format.
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internal void WriteXRefEnty(PdfWriter writer)
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// PDFsharp does not yet support PDF 1.5 object streams.
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// Each line must be exactly 20 bytes long, otherwise Acrobat repairs the file.
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string text = String.Format("{0:0000000000} {1:00000} n\n",
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this.position, this.objectID.GenerationNumber); // this.InUse ? 'n' : 'f');
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writer.WriteRaw(text);
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/// Writes an indirect reference.
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internal override void WriteObject(PdfWriter writer)
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/// Gets or sets the object identifier.
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public PdfObjectID ObjectID
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get { return this.objectID; }
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if (this.objectID != value)
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this.objectID = value;
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if (this.Document != null)
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//PdfXRefTable table = this.Document.xrefTable;
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//table.Remove(this);
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//this.objectID = value;
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PdfObjectID objectID;
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/// Gets the object number of the object identifier.
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public int ObjectNumber
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get { return this.objectID.ObjectNumber; }
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/// Gets the generation number of the object identifier.
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public int GenerationNumber
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get { return this.objectID.GenerationNumber; }
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/// Gets or sets the file position of the related PdfObject.
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get { return this.position; }
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set { this.position = value; }
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int position; // I know it should be long, but I have never seen a 2GB PDF file.
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// get {return this.inUse;}
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// set {this.inUse = value;}
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/// Gets or sets the referenced PdfObject.
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public PdfObject Value
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get { return this.value; }
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// value must never be null
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value.Reference = this;
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/// Hack for dead objects.
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internal void SetObject(PdfObject value)
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/// Gets or sets the document this object belongs to.
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public PdfDocument Document
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get { return this.document; }
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set { this.document = value; }
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PdfDocument document;
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/// Gets a string representing the object identifier.
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public override string ToString()
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return this.objectID.ToString() + " R";
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internal static PdfReferenceComparer Comparer
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get { return new PdfReferenceComparer(); }
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/// Implements a comparer that compares PdfReference objects by their PdfObjectID.
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internal class PdfReferenceComparer : IComparer
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public int Compare(object x, object y)
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PdfReference l = x as PdfReference;
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PdfReference r = y as PdfReference;
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return l.objectID.CompareTo(r.objectID);
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#if UNIQUE_IREF && DEBUG
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static int counter = 0;
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lib/PdfSharp/PdfSharp.Pdf.Advanced/PdfReference.cs
