Add document loading

@@ -7,6 +7,7 @@
 - Add GridPaper widget
 - Improve internal sructure
 - Add some asserts on the TtfParser
+- Add document loading
 
 ## 1.13.0
 

@@ -92,9 +92,10 @@ final file = File("example.pdf");
 await file.writeAsBytes(pdf.save());
 ```
 
-## Encryption and Digital Signature
+## Encryption, Digital Signature, and loading a PDF Document
 
 Encryption using RC4-40, RC4-128, AES-128, and AES-256 is fully supported using a separate library.
 This library also provides SHA1 or SHA-256 Digital Signature using your x509 certificate. The graphic signature is represented by a clickable widget that shows Digital Signature information.
+It implememts a PDF parser to load an existing document and add pages, change pages, and add a signature.
 
 Drop me an email for availability and more information.

@@ -20,6 +20,7 @@ export 'src/border.dart';
 export 'src/color.dart';
 export 'src/colors.dart';
 export 'src/document.dart';
+export 'src/document_parser.dart';
 export 'src/encryption.dart';
 export 'src/exif.dart';
 export 'src/font.dart';

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+import 'dart:collection';
 import 'dart:convert';
 import 'dart:typed_data';
 
@@ -54,6 +55,18 @@ class PdfBool extends PdfDataType {
   void output(PdfStream s) {
     s.putString(value ? 'true' : 'false');
   }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfBool) {
+      return value == other.value;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => value.hashCode;
 }
 
 class PdfNum extends PdfDataType {
@@ -86,6 +99,18 @@ class PdfNum extends PdfDataType {
       s.putString(r);
     }
   }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfNum) {
+      return value == other.value;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => value.hashCode;
 }
 
 class PdfNumList extends PdfDataType {
@@ -102,6 +127,18 @@ class PdfNumList extends PdfDataType {
       PdfNum(values[n]).output(s);
     }
   }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfNumList) {
+      return values == other.values;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => values.hashCode;
 }
 
 enum PdfStringFormat { binary, litteral }
@@ -255,6 +292,18 @@ class PdfString extends PdfDataType {
   void output(PdfStream s) {
     _output(s, value);
   }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfString) {
+      return value == other.value;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => value.hashCode;
 }
 
 class PdfSecString extends PdfString {
@@ -337,6 +386,18 @@ class PdfName extends PdfDataType {
     }
     s.putBytes(bytes);
   }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfName) {
+      return value == other.value;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => value.hashCode;
 }
 
 class PdfNull extends PdfDataType {
@@ -346,6 +407,14 @@ class PdfNull extends PdfDataType {
   void output(PdfStream s) {
     s.putString('null');
   }
+
+  @override
+  bool operator ==(Object other) {
+    return other is PdfNull;
+  }
+
+  @override
+  int get hashCode => null.hashCode;
 }
 
 class PdfIndirect extends PdfDataType {
@@ -359,6 +428,18 @@ class PdfIndirect extends PdfDataType {
   void output(PdfStream s) {
     s.putString('$ser $gen R');
   }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfIndirect) {
+      return ser == other.ser && gen == other.gen;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => ser.hashCode + gen.hashCode;
 }
 
 class PdfArray extends PdfDataType {
@@ -401,6 +482,33 @@ class PdfArray extends PdfDataType {
     }
     s.putString(']');
   }
+
+  /// Make all values unique, preserving the order
+  void uniq() {
+    if (values.length <= 1) {
+      return;
+    }
+
+    // ignore: prefer_collection_literals
+    final uniques = LinkedHashMap<PdfDataType, bool>();
+    for (final s in values) {
+      uniques[s] = true;
+    }
+    values.clear();
+    values.addAll(uniques.keys);
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfArray) {
+      return values == other.values;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => values.hashCode;
 }
 
 class PdfDict extends PdfDataType {
@@ -427,6 +535,10 @@ class PdfDict extends PdfDataType {
     values[k] = v;
   }
 
+  PdfDataType operator [](String k) {
+    return values[k];
+  }
+
   @override
   void output(PdfStream s) {
     s.putBytes(const <int>[0x3c, 0x3c]);
@@ -443,6 +555,39 @@ class PdfDict extends PdfDataType {
   bool containsKey(String key) {
     return values.containsKey(key);
   }
+
+  void merge(PdfDict other) {
+    for (final key in other.values.keys) {
+      final value = other[key];
+      final current = values[key];
+      if (current == null) {
+        values[key] = value;
+      } else if (value is PdfArray && current is PdfArray) {
+        current.values.addAll(value.values);
+        current.uniq();
+      } else if (value is PdfDict && current is PdfDict) {
+        current.merge(value);
+      } else {
+        values[key] = value;
+      }
+    }
+  }
+
+  void addAll(PdfDict other) {
+    values.addAll(other.values);
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfDict) {
+      return values == other.values;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => values.hashCode;
 }
 
 class PdfColorType extends PdfDataType {
@@ -468,4 +613,16 @@ class PdfColorType extends PdfDataType {
       ]).output(s);
     }
   }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is PdfColorType) {
+      return color == other.color;
+    }
+
+    return false;
+  }
+
+  @override
+  int get hashCode => color.hashCode;
 }

@@ -23,6 +23,7 @@ import '../io/interface.dart'
     if (dart.library.io) '../io/vm.dart'
     if (dart.library.js) '../io/js.dart';
 import 'catalog.dart';
+import 'document_parser.dart';
 import 'encryption.dart';
 import 'font.dart';
 import 'graphic_state.dart';
@@ -70,7 +71,8 @@ class PdfDocument {
     PdfPageMode pageMode = PdfPageMode.none,
     DeflateCallback deflate,
     bool compress = true,
-  }) : deflate = compress ? (deflate ?? defaultDeflate) : null {
+  })  : deflate = compress ? (deflate ?? defaultDeflate) : null,
+        prev = null {
     _objser = 1;
 
     // Now create some standard objects
@@ -79,9 +81,30 @@ class PdfDocument {
     catalog = PdfCatalog(this, pdfPageList, pageMode, pdfNames);
   }
 
+  PdfDocument.load(
+    this.prev, {
+    PdfPageMode pageMode = PdfPageMode.none,
+    DeflateCallback deflate,
+    bool compress = true,
+  }) : deflate = compress ? (deflate ?? defaultDeflate) : null {
+    _objser = prev.size;
+
+    // Now create some standard objects
+    pdfPageList = PdfPageList(this);
+    pdfNames = PdfNames(this);
+    catalog = PdfCatalog(this, pdfPageList, pageMode, pdfNames);
+
+    // Import the existing document
+    prev.mergeDocument(this);
+  }
+
+  final PdfDocumentParserBase prev;
+
   /// This is used to allocate objects a unique serial number in the document.
   int _objser;
 
+  int get objser => _objser;
+
   /// This vector contains each indirect object within the document.
   final Set<PdfObject> objects = <PdfObject>{};
 
@@ -146,7 +169,7 @@ class PdfDocument {
   /// This returns a specific page. It's used mainly when using a
   /// Serialized template file.
   PdfPage page(int page) {
-    return pdfPageList.getPage(page);
+    return pdfPageList.pages[page];
   }
 
   /// The root outline
@@ -182,6 +205,9 @@ class PdfDocument {
   /// Generate the PDF document as a memory file
   Uint8List save() {
     final os = PdfStream();
+    if (prev != null) {
+      os.putBytes(prev.bytes);
+    }
     _write(os);
     return os.output();
   }

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed 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.
+ */
+
+import 'dart:typed_data';
+
+import 'package:pdf/src/document.dart';
+
+/// Base class for loading an existing PDF document.
+abstract class PdfDocumentParserBase {
+  /// Create a Document loader instance
+  PdfDocumentParserBase(this.bytes);
+
+  /// The existing PDF document content
+  final Uint8List bytes;
+
+  /// The objects size of the existing PDF document
+  int get size;
+
+  /// The offset of the previous cross reference table
+  int get xrefOffset;
+
+  /// Import the existing objects into the new PDF document
+  void mergeDocument(PdfDocument pdfDocument);
+}

@@ -138,6 +138,14 @@ mixin PdfGraphicStream on PdfObject {
       resources['/ExtGState'] = pdfDocument.graphicStates.ref();
     }
 
+    if (params.containsKey('/Resources')) {
+      final res = params['/Resources'];
+      if (res is PdfDict) {
+        res.merge(resources);
+        return;
+      }
+    }
+
     params['/Resources'] = resources;
   }
 }

@@ -83,4 +83,7 @@ class PdfObject {
 
   /// Returns the unique serial number in Pdf format
   PdfIndirect ref() => PdfIndirect(objser, objgen);
+
+  @override
+  String toString() => '$runtimeType $params';
 }

@@ -72,26 +72,23 @@ class PdfOutput {
     final xref = os.offset;
     os.putString('xref\n');
 
-    // Now scan through the offsets list. The should be in sequence,
-    // but just in case:
+    // Now scan through the offsets list. They should be in sequence.
+    offsets.sort((a, b) => a.id.compareTo(b.id));
+
     var firstid = 0; // First id in block
-    var lastid = -1; // The last id used
+    var lastid = 0; // The last id used
     final block = <PdfXref>[]; // xrefs in this block
 
     // We need block 0 to exist
     block.add(PdfXref(0, 0, generation: 65535));
 
     for (var x in offsets) {
-      if (firstid == -1) {
-        firstid = x.id;
-      }
-
-      // check to see if block is in range (-1 means empty)
-      if (lastid > -1 && x.id != (lastid + 1)) {
+      // check to see if block is in range
+      if (lastid != null && x.id != (lastid + 1)) {
         // no, so write this block, and reset
         writeblock(firstid, block);
         block.clear();
-        firstid = -1;
+        firstid = x.id;
       }
 
       // now add to block
@@ -100,9 +97,7 @@ class PdfOutput {
     }
 
     // now write the last block
-    if (firstid > -1) {
-      writeblock(firstid, block);
-    }
+    writeblock(firstid, block);
 
     // now the trailer object
     os.putString('trailer\n');
@@ -110,7 +105,7 @@ class PdfOutput {
     final params = PdfDict();
 
     // the number of entries (REQUIRED)
-    params['/Size'] = PdfNum(offsets.length + 1);
+    params['/Size'] = PdfNum(rootID.pdfDocument.objser);
 
     // the /Root catalog indirect reference (REQUIRED)
     if (rootID != null) {
@@ -132,6 +127,10 @@ class PdfOutput {
       params['/Encrypt'] = encryptID.ref();
     }
 
+    if (rootID.pdfDocument.prev != null) {
+      params['/Prev'] = PdfNum(rootID.pdfDocument.prev.xrefOffset);
+    }
+
     // end the trailer object
     params.output(os);
     os.putString('\nstartxref\n$xref\n%%EOF\n');

@@ -27,9 +27,16 @@ import 'page_format.dart';
 class PdfPage extends PdfObject with PdfGraphicStream {
   /// This constructs a Page object, which will hold any contents for this
   /// page.
-  PdfPage(PdfDocument pdfDocument, {this.pageFormat = PdfPageFormat.standard})
-      : super(pdfDocument, type: '/Page') {
-    pdfDocument.pdfPageList.pages.add(this);
+  PdfPage(
+    PdfDocument pdfDocument, {
+    this.pageFormat = PdfPageFormat.standard,
+    int index,
+  }) : super(pdfDocument, type: '/Page') {
+    if (index != null) {
+      pdfDocument.pdfPageList.pages.insert(index, this);
+    } else {
+      pdfDocument.pdfPageList.pages.add(this);
+    }
   }
 
   /// This is this page format, ie the size of the page, margins, and rotation
@@ -38,10 +45,6 @@ class PdfPage extends PdfObject with PdfGraphicStream {
   /// This holds the contents of the page.
   List<PdfObjectStream> contents = <PdfObjectStream>[];
 
-  /// Object ID that contains a thumbnail sketch of the page.
-  /// -1 indicates no thumbnail.
-  PdfObject thumbnail;
-
   /// This holds any Annotations contained within this page.
   List<PdfAnnot> annotations = <PdfAnnot>[];
 
@@ -72,30 +75,38 @@ class PdfPage extends PdfObject with PdfGraphicStream {
     params['/MediaBox'] =
         PdfArray.fromNum(<double>[0, 0, pageFormat.width, pageFormat.height]);
 
-    // Rotation (if not zero)
-//        if(rotate!=0) {
-//            os.write("/Rotate ");
-//            os.write(Integer.toString(rotate).getBytes());
-//            os.write("\n");
-//        }
-
-    // the /Contents pages object
+    // The graphic operations to draw the page
     if (contents.isNotEmpty) {
-      if (contents.length == 1) {
-        params['/Contents'] = contents.first.ref();
-      } else {
-        params['/Contents'] = PdfArray.fromObjects(contents);
+      final contentList = PdfArray.fromObjects(contents);
+
+      if (params.containsKey('/Contents')) {
+        final prevContent = params['/Contents'];
+        if (prevContent is PdfArray) {
+          contentList.values.insertAll(0, prevContent.values);
+        } else {
+          contentList.values.insert(0, prevContent);
+        }
       }
-    }
 
-    // The thumbnail
-    if (thumbnail != null) {
-      params['/Thumb'] = thumbnail.ref();
+      contentList.uniq();
+
+      if (contentList.values.length == 1) {
+        params['/Contents'] = contentList.values.first;
+      } else {
+        params['/Contents'] = contentList;
+      }
     }
 
     // The /Annots object
     if (annotations.isNotEmpty) {
-      params['/Annots'] = PdfArray.fromObjects(annotations);
+      if (params.containsKey('/Annots')) {
+        final annotsList = params['/Annots'];
+        if (annotsList is PdfArray) {
+          annotsList.values.addAll(PdfArray.fromObjects(annotations).values);
+        }
+      } else {
+        params['/Annots'] = PdfArray.fromObjects(annotations);
+      }
     }
   }
 }

@@ -17,10 +17,10 @@
  */
 
 import 'package:meta/meta.dart';
-import 'package:pdf/pdf.dart';
 
 import 'data_types.dart';
 import 'document.dart';
+import 'function.dart';
 import 'graphic_stream.dart';
 import 'graphics.dart';
 import 'rect.dart';

@@ -39,4 +39,7 @@ class PdfXref {
     }
     return rs + ' n ';
   }
+
+  @override
+  String toString() => '$runtimeType $id $generation $offset';
 }

@@ -22,18 +22,18 @@ import 'page.dart';
 import 'theme.dart';
 
 class Document {
-  Document(
-      {PdfPageMode pageMode = PdfPageMode.none,
-      DeflateCallback deflate,
-      bool compress = true,
-      this.theme,
-      String title,
-      String author,
-      String creator,
-      String subject,
-      String keywords,
-      String producer})
-      : document = PdfDocument(
+  Document({
+    PdfPageMode pageMode = PdfPageMode.none,
+    DeflateCallback deflate,
+    bool compress = true,
+    this.theme,
+    String title,
+    String author,
+    String creator,
+    String subject,
+    String keywords,
+    String producer,
+  }) : document = PdfDocument(
           pageMode: pageMode,
           deflate: deflate,
           compress: compress,
@@ -44,13 +44,51 @@ class Document {
         subject != null ||
         keywords != null ||
         producer != null) {
-      document.info = PdfInfo(document,
-          title: title,
-          author: author,
-          creator: creator,
-          subject: subject,
-          keywords: keywords,
-          producer: producer);
+      document.info = PdfInfo(
+        document,
+        title: title,
+        author: author,
+        creator: creator,
+        subject: subject,
+        keywords: keywords,
+        producer: producer,
+      );
+    }
+  }
+
+  Document.load(
+    PdfDocumentParserBase parser, {
+    PdfPageMode pageMode = PdfPageMode.none,
+    DeflateCallback deflate,
+    bool compress = true,
+    this.theme,
+    String title,
+    String author,
+    String creator,
+    String subject,
+    String keywords,
+    String producer,
+  }) : document = PdfDocument.load(
+          parser,
+          pageMode: pageMode,
+          deflate: deflate,
+          compress: compress,
+        ) {
+    if (title != null ||
+        author != null ||
+        creator != null ||
+        subject != null ||
+        keywords != null ||
+        producer != null) {
+      document.info = PdfInfo(
+        document,
+        title: title,
+        author: author,
+        creator: creator,
+        subject: subject,
+        keywords: keywords,
+        producer: producer,
+      );
     }
   }
 
@@ -64,8 +102,13 @@ class Document {
 
   bool _paint = false;
 
-  void addPage(Page page) {
-    page.generate(this);
+  void addPage(Page page, {int index}) {
+    page.generate(this, index: index);
+    _pages.add(page);
+  }
+
+  void editPage(int index, Page page) {
+    page.generate(this, index: index, insert: false);
     _pages.add(page);
   }
 

@@ -150,7 +150,7 @@ class MultiPage extends Page {
   }
 
   @override
-  void generate(Document document) {
+  void generate(Document document, {bool insert = true, int index}) {
     if (_buildList == null) {
       return;
     }
@@ -178,7 +178,7 @@ class MultiPage extends Page {
     Context context;
     double offsetEnd;
     double offsetStart;
-    var index = 0;
+    var _index = 0;
     var sameCount = 0;
     final baseContext =
         Context(document: document.document).inheritFromAll(<Inherited>[
@@ -189,8 +189,8 @@ class MultiPage extends Page {
     final children = _buildList(baseContext);
     WidgetContext widgetContext;
 
-    while (index < children.length) {
-      final child = children[index];
+    while (_index < children.length) {
+      final child = children[_index];
       var canSpan = false;
       if (child is SpanningWidget) {
         canSpan = child.canSpan;
@@ -207,7 +207,11 @@ class MultiPage extends Page {
 
       // Create a new page if we don't already have one
       if (context == null || child is NewPage) {
-        final pdfPage = PdfPage(document.document, pageFormat: pageFormat);
+        final pdfPage = PdfPage(
+          document.document,
+          pageFormat: pageFormat,
+          index: index == null ? null : (index++),
+        );
         context =
             baseContext.copyWith(page: pdfPage, canvas: pdfPage.getGraphics());
 
@@ -293,7 +297,7 @@ class MultiPage extends Page {
         // Has it finished spanning?
         if (!span.hasMoreWidgets) {
           sameCount = 0;
-          index++;
+          _index++;
         }
 
         // Schedule a new page
@@ -313,7 +317,7 @@ class MultiPage extends Page {
 
       offsetStart -= child.box.height;
       sameCount = 0;
-      index++;
+      _index++;
     }
   }
 

@@ -96,8 +96,17 @@ class Page {
       ..fillPath();
   }
 
-  void generate(Document document) {
-    _pdfPage = PdfPage(document.document, pageFormat: pageFormat);
+  void generate(Document document, {bool insert = true, int index}) {
+    if (index != null) {
+      if (insert) {
+        _pdfPage =
+            PdfPage(document.document, pageFormat: pageFormat, index: index);
+      } else {
+        _pdfPage = document.document.page(index);
+      }
+    } else {
+      _pdfPage = PdfPage(document.document, pageFormat: pageFormat);
+    }
   }
 
   void postProcess(Document document) {

@@ -4,7 +4,7 @@ description: A pdf producer for Dart. It can create pdf files for both web or fl
 homepage: https://github.com/DavBfr/dart_pdf/tree/master/pdf
 repository: https://github.com/DavBfr/dart_pdf
 issue_tracker: https://github.com/DavBfr/dart_pdf/issues
-version: 1.13.0
+version: 1.14.0
 
 environment:
   sdk: ">=2.3.0 <3.0.0"

@@ -183,9 +183,10 @@ final title = 'Flutter Demo';
 await Printing.layoutPdf(onLayout: (format) => _generatePdf(format, title));
 ```
 
-## Encryption and Digital Signature
+## Encryption, Digital Signature, and loading a PDF Document
 
 Encryption using RC4-40, RC4-128, AES-128, and AES-256 is fully supported using a separate library.
 This library also provides SHA1 or SHA-256 Digital Signature using your x509 certificate. The graphic signature is represented by a clickable widget that shows Digital Signature information.
+It implememts a PDF parser to load an existing document and add pages, change pages, and add a signature.
 
 Drop me an email for availability and more information.