Added withReadStream option to load a file in chunks (useful for large files)

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 2.1.0
+Adds `withReadStream` that allows bigger files to be streamed read into a `Stream<List<int>>`. Thanks @redsolver.
+
 ## 2.0.13
 Updates `extension` helper getter to use the `name` property instead of `path`, since the latest isn't available on the Web, hence, the extension wouldn't be as well. Thank you @markgrancapal.
 

lib/src/file_picker.dart

@@ -49,6 +49,9 @@ abstract class FilePicker extends PlatformInterface {
   /// If [withData] is set, picked files will have its byte data immediately available on memory as [Uint8List]
   /// which can be useful if you are picking it for server upload or similar.
   ///
+  /// If [withReadStream] is set, picked files will have its byte data available as a [Stream<List<int>>]
+  /// which can be useful for uploading and processing large files.
+  ///
   /// If you want to track picking status, for example, because some files may take some time to be
   /// cached (particularly those picked from cloud providers), you may want to set [onFileLoading] handler
   /// that will give you the current status of picking.
@@ -64,6 +67,7 @@ abstract class FilePicker extends PlatformInterface {
     bool allowCompression,
     bool allowMultiple = false,
     bool withData,
+    bool withReadStream,
   }) async =>
       throw UnimplementedError('pickFiles() has not been implemented.');
 

lib/src/file_picker_io.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:io';
 
 import 'package:file_picker/file_picker.dart';
 import 'package:file_picker/src/platform_file.dart';
@@ -25,6 +26,7 @@ class FilePickerIO extends FilePicker {
     bool allowCompression = true,
     bool allowMultiple = false,
     bool withData = false,
+    bool withReadStream = false,
   }) =>
       _getPath(
         type,
@@ -33,6 +35,7 @@ class FilePickerIO extends FilePicker {
         allowedExtensions,
         onFileLoading,
         withData,
+        withReadStream,
       );
 
   @override
@@ -59,6 +62,7 @@ class FilePickerIO extends FilePicker {
     List<String> allowedExtensions,
     Function(FilePickerStatus) onFileLoading,
     bool withData,
+    bool withReadStream,
   ) async {
     final String type = describeEnum(fileType);
     if (type != 'custom' && (allowedExtensions?.isNotEmpty ?? false)) {
@@ -87,8 +91,20 @@ class FilePickerIO extends FilePicker {
         return null;
       }
 
-      return FilePickerResult(
+      final List<PlatformFile> platformFiles = <PlatformFile>[];
-          result.map((file) => PlatformFile.fromMap(file)).toList());
+
+      for (final platformFileMap in result) {
+        platformFiles.add(
+          PlatformFile.fromMap(
+            platformFileMap,
+            readStream: withReadStream
+                ? File(platformFileMap['path']).openRead()
+                : null,
+          ),
+        );
+      }
+
+      return FilePickerResult(platformFiles);
     } on PlatformException catch (e) {
       print('[$_tag] Platform exception: $e');
       rethrow;

lib/src/file_picker_web.dart

@@ -12,6 +12,8 @@ class FilePickerWeb extends FilePicker {
   Element _target;
   final String _kFilePickerInputsDomId = '__file_picker_web-file-input';
 
+  final int _readStreamChunkSize = 1000 * 1000; // 1 MB
+
   static final FilePickerWeb platform = FilePickerWeb._();
 
   FilePickerWeb._() {
@@ -43,6 +45,7 @@ class FilePickerWeb extends FilePicker {
     Function(FilePickerStatus) onFileLoading,
     bool allowCompression,
     bool withData = true,
+    bool withReadStream = false,
   }) async {
     final Completer<List<PlatformFile>> filesCompleter =
         Completer<List<PlatformFile>>();
@@ -63,12 +66,18 @@ class FilePickerWeb extends FilePicker {
       final List<File> files = uploadInput.files;
       final List<PlatformFile> pickedFiles = [];
 
-      void addPickedFile(File file, Uint8List bytes, String path) {
+      void addPickedFile(
+        File file,
+        Uint8List bytes,
+        String path,
+        Stream<List<int>> readStream,
+      ) {
         pickedFiles.add(PlatformFile(
           name: file.name,
           path: path,
-          size: bytes != null ? bytes.length ~/ 1024 : -1,
+          size: bytes != null ? bytes.length ~/ 1024 : file.size,
           bytes: bytes,
+          readStream: readStream,
         ));
 
         if (pickedFiles.length >= files.length) {
@@ -77,10 +86,15 @@ class FilePickerWeb extends FilePicker {
       }
 
       files.forEach((File file) {
+        if (withReadStream) {
+          addPickedFile(file, null, null, _openFileReadStream(file));
+          return;
+        }
+
         if (!withData) {
           final FileReader reader = FileReader();
           reader.onLoadEnd.listen((e) {
-            addPickedFile(file, null, reader.result);
+            addPickedFile(file, null, reader.result, null);
           });
           reader.readAsDataUrl(file);
           return;
@@ -88,7 +102,7 @@ class FilePickerWeb extends FilePicker {
 
         final FileReader reader = FileReader();
         reader.onLoadEnd.listen((e) {
-          addPickedFile(file, reader.result, null);
+          addPickedFile(file, reader.result, null, null);
         });
         reader.readAsArrayBuffer(file);
       });
@@ -129,4 +143,20 @@ class FilePickerWeb extends FilePicker {
     }
     return '';
   }
+
+  Stream<List<int>> _openFileReadStream(File file) async* {
+    final reader = FileReader();
+
+    int start = 0;
+    while (start < file.size) {
+      final end = start + _readStreamChunkSize > file.size
+          ? file.size
+          : start + _readStreamChunkSize;
+      final blob = file.slice(start, end);
+      reader.readAsArrayBuffer(blob);
+      await reader.onLoad.first;
+      yield reader.result;
+      start += _readStreamChunkSize;
+    }
+  }
 }

lib/src/platform_file.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:typed_data';
 
 class PlatformFile {
@@ -5,10 +6,11 @@ class PlatformFile {
     this.path,
     this.name,
     this.bytes,
+    this.readStream,
     this.size,
   });
 
-  PlatformFile.fromMap(Map data)
+  PlatformFile.fromMap(Map data, {this.readStream})
       : this.path = data['path'],
         this.name = data['name'],
         this.bytes = data['bytes'],
@@ -28,6 +30,9 @@ class PlatformFile {
   /// or easily upload to somewhere else.
   final Uint8List bytes;
 
+  /// File content as stream
+  final Stream<List<int>> readStream;
+
   /// The file size in KB.
   final int size;
 

pubspec.yaml

@@ -1,7 +1,7 @@
 name: file_picker
 description: A package that allows you to use a native file explorer to pick single or multiple absolute file paths, with extension filtering support.
 homepage: https://github.com/miguelpruivo/plugins_flutter_file_picker
-version: 2.0.13
+version: 2.1.0
 
 dependencies:
   flutter: