158 lines
7.4 KiB
C#
158 lines
7.4 KiB
C#
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#region PDFsharp - A .NET library for processing PDF
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//
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// Authors:
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// Stefan Lange
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//
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// Copyright (c) 2005-2017 empira Software GmbH, Cologne Area (Germany)
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//
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// http://www.pdfsharp.com
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// http://sourceforge.net/projects/pdfsharp
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//
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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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//
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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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//
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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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#endregion
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using System.Collections.Generic;
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using System.Diagnostics;
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namespace PdfSharp.Pdf.Advanced
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{
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/// <summary>
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/// Represents a PDF cross-reference stream.
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/// </summary>
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internal sealed class PdfCrossReferenceStream : PdfTrailer // Reference: 3.4.7 Cross-Reference Streams / Page 106
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{
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/// <summary>
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/// Initializes a new instance of the <see cref="PdfObjectStream"/> class.
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/// </summary>
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public PdfCrossReferenceStream(PdfDocument document)
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: base(document)
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{
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#if DEBUG && CORE
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if (Internal.PdfDiagnostics.TraceXrefStreams)
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{
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Debug.WriteLine("PdfCrossReferenceStream created.");
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}
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#endif
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}
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public readonly List<CrossReferenceStreamEntry> Entries = new List<CrossReferenceStreamEntry>();
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public struct CrossReferenceStreamEntry
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{
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// Reference: TABLE 3.16 Entries in a cross-reference stream / Page 109
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public uint Type; // 0, 1, or 2.
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public uint Field2;
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public uint Field3;
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}
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/// <summary>
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/// Predefined keys for cross-reference dictionaries.
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/// </summary>
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public new class Keys : PdfTrailer.Keys // Reference: TABLE 3.15 Additional entries specific to a cross-reference stream dictionary / Page 107
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{
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/// <summary>
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/// (Required) The type of PDF object that this dictionary describes;
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/// must be XRef for a cross-reference stream.
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/// </summary>
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[KeyInfo(KeyType.Name | KeyType.Required, FixedValue = "XRef")]
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public const string Type = "/Type";
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/// <summary>
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/// (Required) The number one greater than the highest object number
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/// used in this section or in any section for which this is an update.
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/// It is equivalent to the Size entry in a trailer dictionary.
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/// </summary>
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[KeyInfo(KeyType.Integer | KeyType.Required)]
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public new const string Size = "/Size";
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/// <summary>
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/// (Optional) An array containing a pair of integers for each subsection in this section.
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/// The first integer is the first object number in the subsection; the second integer
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/// is the number of entries in the subsection.
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/// The array is sorted in ascending order by object number. Subsections cannot overlap;
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/// an object number may have at most one entry in a section.
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/// Default value: [0 Size].
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/// </summary>
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[KeyInfo(KeyType.Array | KeyType.Optional)]
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public const string Index = "/Index";
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/// <summary>
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/// (Present only if the file has more than one cross-reference stream; not meaningful in
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/// hybrid-reference files) The byte offset from the beginning of the file to the beginning
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/// of the previous cross-reference stream. This entry has the same function as the Prev
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/// entry in the trailer dictionary.
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/// </summary>
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[KeyInfo(KeyType.Integer | KeyType.Optional)]
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public new const string Prev = "/Prev";
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/// <summary>
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/// (Required) An array of integers representing the size of the fields in a single
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/// cross-reference entry. The table describes the types of entries and their fields.
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/// For PDF 1.5, W always contains three integers; the value of each integer is the
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/// number of bytes (in the decoded stream) of the corresponding field. For example,
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/// [1 2 1] means that the fields are one byte, two bytes, and one byte, respectively.
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///
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/// A value of zero for an element in the W array indicates that the corresponding field
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/// is not present in the stream, and the default value is used, if there is one. If the
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/// first element is zero, the type field is not present, and it defaults to type 1.
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///
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/// The sum of the items is the total length of each entry; it can be used with the
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/// Indexarray to determine the starting position of each subsection.
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///
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/// Note: Different cross-reference streams in a PDF file may use different values for W.
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///
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/// Entries in a cross-reference stream.
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///
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/// TYPE FIELD DESCRIPTION
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/// 0 1 The type of this entry, which must be 0. Type 0 entries define the linked list of free objects (corresponding to f entries in a cross-reference table).
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/// 2 The object number of the next free object.
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/// 3 The generation number to use if this object number is used again.
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/// 1 1 The type of this entry, which must be 1. Type 1 entries define objects that are in use but are not compressed (corresponding to n entries in a cross-reference table).
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/// 2 The byte offset of the object, starting from the beginning of the file.
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/// 3 The generation number of the object. Default value: 0.
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/// 2 1 The type of this entry, which must be 2. Type 2 entries define compressed objects.
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/// 2 The object number of the object stream in which this object is stored. (The generation number of the object stream is implicitly 0.)
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/// 3 The index of this object within the object stream.
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/// </summary>
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[KeyInfo(KeyType.Array | KeyType.Required)]
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public const string W = "/W";
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/// <summary>
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/// Gets the KeysMeta for these keys.
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/// </summary>
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public static new DictionaryMeta Meta
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{
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get { return _meta ?? (_meta = CreateMeta(typeof(Keys))); }
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}
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static DictionaryMeta _meta;
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}
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/// <summary>
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/// Gets the KeysMeta of this dictionary type.
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/// </summary>
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internal override DictionaryMeta Meta
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{
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get { return Keys.Meta; }
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}
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}
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}
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