Feature: output to file stream

pdf/lib/src/pdf/document.dart

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+import 'dart:io';
 import 'dart:math' as math;
 import 'dart:typed_data';
 
@@ -251,10 +252,22 @@ class PdfDocument {
     }
   }
 
+  /// Generate the PDF document in a file
+  Future<void> saveFile(File file) async {
+    return pdfCompute(() async {
+      final os = PdfStreamFile(file);
+      if (prev != null) {
+        os.putBytes(prev!.bytes);
+      }
+      await _write(os);
+      os.close();
+    });
+  }
+
   /// Generate the PDF document as a memory file
   Future<Uint8List> save() async {
     return pdfCompute(() async {
-      final os = PdfStream();
+      final os = PdfStreamBuffer();
       if (prev != null) {
         os.putBytes(prev!.bytes);
       }

pdf/lib/src/pdf/format/base.dart

@@ -28,8 +28,8 @@ abstract class PdfDataType {
 
   void output(PdfObjectBase o, PdfStream s, [int? indent]);
 
-  PdfStream _toStream([int? indent]) {
-    final s = PdfStream();
+  PdfStreamBuffer _toStream([int? indent]) {
+    final s = PdfStreamBuffer();
     output(
       PdfObjectBase(
         objser: 0,

pdf/lib/src/pdf/format/diagnostic.dart

@@ -43,7 +43,7 @@ mixin PdfDiagnostic {
   void writeDebug(PdfStream os) {
     assert(() {
       if (_offset != null) {
-        final o = PdfStream();
+        final o = PdfStreamBuffer();
         _properties.forEach(o.putComment);
         final b = o.output();
         os.setBytes(

pdf/lib/src/pdf/format/stream.dart

@@ -14,9 +14,46 @@
  * limitations under the License.
  */
 
+import 'dart:io';
 import 'dart:typed_data';
 
-class PdfStream {
+abstract class PdfStream {
+  void putByte(int s);
+
+  void putBytes(List<int> s);
+
+  void setBytes(int offset, Iterable<int> iterable);
+
+  void putStream(PdfStreamBuffer s);
+
+  int get offset;
+
+  void putString(String? s) {
+    assert(() {
+      for (final codeUnit in s!.codeUnits) {
+        if (codeUnit > 0x7f) {
+          return false;
+        }
+      }
+      return true;
+    }());
+    putBytes(s!.codeUnits);
+  }
+
+  void putComment(String s) {
+    if (s.isEmpty) {
+      putByte(0x0a);
+    } else {
+      for (final l in s.split('\n')) {
+        if (l.isNotEmpty) {
+          putBytes('% $l\n'.codeUnits);
+        }
+      }
+    }
+  }
+}
+
+class PdfStreamBuffer extends PdfStream {
   static const int _grow = 65536;
 
   Uint8List _stream = Uint8List(_grow);
@@ -34,50 +71,71 @@ class PdfStream {
     _stream = newBuffer;
   }
 
+  @override
   void putByte(int s) {
     _ensureCapacity(1);
     _stream[_offset++] = s;
   }
 
+  @override
   void putBytes(List<int> s) {
     _ensureCapacity(s.length);
     _stream.setAll(_offset, s);
     _offset += s.length;
   }
 
+  @override
   void setBytes(int offset, Iterable<int> iterable) {
     _stream.setAll(offset, iterable);
   }
 
-  void putStream(PdfStream s) {
+  @override
+  void putStream(PdfStreamBuffer s) {
     putBytes(s._stream);
   }
 
+  @override
   int get offset => _offset;
 
   Uint8List output() => _stream.sublist(0, _offset);
+}
 
-  void putString(String? s) {
-    assert(() {
-      for (final codeUnit in s!.codeUnits) {
-        if (codeUnit > 0x7f) {
-          return false;
-        }
-      }
-      return true;
-    }());
-    putBytes(s!.codeUnits);
+class PdfStreamFile extends PdfStream {
+  PdfStreamFile(File file) {
+    _raf = file.openSync(mode: FileMode.write);
   }
 
-  void putComment(String s) {
-    if (s.isEmpty) {
-      putByte(0x0a);
-    } else {
-      for (final l in s.split('\n')) {
-        if (l.isNotEmpty) {
-          putBytes('% $l\n'.codeUnits);
-        }
-      }
-    }
+  late RandomAccessFile _raf;
+
+  void close() {
+    _raf.closeSync();
+  }
+
+  @override
+  void putByte(int s) {
+    _raf.writeByteSync(s);
+  }
+
+  @override
+  void putBytes(List<int> s) {
+    _raf.writeFromSync(s);
+  }
+
+  @override
+  void setBytes(int offset, Iterable<int> iterable) {
+    final originalOffset = _raf.positionSync();
+    _raf.setPositionSync(offset);
+    _raf.writeFromSync(iterable.toList());
+    _raf.setPositionSync(originalOffset);
+  }
+
+  @override
+  void putStream(PdfStreamBuffer s) {
+    putBytes(s._stream);
+  }
+
+  @override
+  int get offset {
+    return _raf.positionSync();
   }
 }

pdf/lib/src/pdf/format/string.dart

@@ -39,7 +39,7 @@ class PdfString extends PdfDataType {
   }
 
   factory PdfString.fromStream(
-    PdfStream value, {
+    PdfStreamBuffer value, {
     PdfStringFormat format = PdfStringFormat.literal,
     bool encrypted = true,
   }) {

pdf/lib/src/pdf/obj/annotation.dart

@@ -81,7 +81,7 @@ class PdfChoiceField extends PdfAnnotWidget {
       params['/V'] = const PdfNull();
     }
 
-    final buf = PdfStream();
+    final buf = PdfStreamBuffer();
     final g = PdfGraphics(page, buf);
     g.setFillColor(textColor);
     g.setFont(font, fontSize);
@@ -928,7 +928,7 @@ class PdfTextField extends PdfFormField {
       params['/MaxLen'] = PdfNum(maxLength!);
     }
 
-    final buf = PdfStream();
+    final buf = PdfStreamBuffer();
     final g = PdfGraphics(page, buf);
     g.setFillColor(textColor);
     g.setFont(font, fontSize);

pdf/lib/src/pdf/obj/object_stream.dart

@@ -36,7 +36,7 @@ class PdfObjectStream extends PdfObject<PdfDict> {
         );
 
   /// This holds the stream's content.
-  final PdfStream buf = PdfStream();
+  final PdfStreamBuffer buf = PdfStreamBuffer();
 
   /// defines if the stream needs to be converted to ascii85
   final bool isBinary;

pdf/lib/src/widgets/document.dart

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:xml/xml.dart';
@@ -124,6 +125,16 @@ class Document {
     _pages.add(page);
   }
 
+  Future<void> saveFile(File file) async {
+    if (!_paint) {
+      for (final page in _pages) {
+        page.postProcess(this);
+      }
+      _paint = true;
+    }
+    await document.saveFile(file);
+  }
+
   Future<Uint8List> save() async {
     if (!_paint) {
       for (final page in _pages) {

pdf/lib/src/widgets/page.dart

@@ -69,7 +69,7 @@ class Page {
 
   PageOrientation get orientation => pageTheme.orientation;
 
-  final BuildCallback _build;
+  BuildCallback? _build;
 
   ThemeData? get theme => pageTheme.theme;
 
@@ -81,6 +81,8 @@ class Page {
 
   EdgeInsets? get resolvedMargin => margin?.resolve(pageTheme.textDirection);
 
+  bool processed = false;
+
   @protected
   void debugPaint(Context context) {
     final _margin = resolvedMargin!;
@@ -113,6 +115,11 @@ class Page {
   }
 
   void postProcess(Document document) {
+    if (processed) {
+      return;
+    }
+    assert(_build != null);
+
     final canvas = _pdfPage!.getGraphics();
     canvas.reset();
     final _margin = resolvedMargin;
@@ -139,7 +146,7 @@ class Page {
     Widget? content;
     Widget? foreground;
 
-    content = _build(context);
+    content = _build!(context);
 
     final size = layout(content, context, constraints);
 
@@ -181,6 +188,8 @@ class Page {
     if (foreground != null) {
       paint(foreground, context);
     }
+    processed = true;
+    _build = null;
   }
 
   @protected