file_streamer

A high-performance, constant-memory file streamer for Flutter and Dart. It avoids pre-loading the entire file into RAM and instead pipes data directly as a stream.

Usage

import 'dart:typed_data';
import 'package:file_streamer/file_streamer.dart';
import 'package:http/http.dart' as http;

Future<void> main() async {
  // 1. Pick files
  final result = await FileStreamer.pickFiles(
    const PickerOptions(
      allowMultiple: true,
      filters: [FileTypeFilter.images],
    ),
  );

  if (result.isEmpty) return;

  // 2 + 3. Stream and upload each file
  for (final file in result.files) {
    print('Uploading: ${file.name} (${file.size} bytes)');

    final stream = FileStreamer.openReadStream(
      file,
      options: const ReadStreamOptions(chunkSize: 512 * 1024), // 512 KB
    );

    final request = http.StreamedRequest(
      'POST',
      Uri.parse('https://httpbin.org/post'),
    );

    request.headers['Content-Type'] = 'application/octet-stream';
    request.contentLength = file.size;

    int uploaded = 0;

    final progressStream = stream.map((Uint8List chunk) {
      uploaded += chunk.length;
      final progress = file.size > 0
          ? (uploaded / file.size * 100).toStringAsFixed(1)
          : '0.0';

      print('${file.name}: $progress%');
      return chunk;
    });

    final responseFuture = request.send();

    await request.sink.addStream(progressStream);
    await request.sink.close();

    final response = await responseFuture;
    await response.stream.drain();

    print('${file.name}: done (${response.statusCode})\n');
  }
}

Find complete flutter and dart examples in the example folder.

Features

• Constant-RAM: Handles 2GB+ files with the same memory footprint as a 10KB file.
• True Streaming: Pipes data straight from the OS buffer to a Dart Stream<Uint8List>.
• Upload-Ready: Directly feed network requests with minimal intermediate RAM overhead.
• Modern Standards: Leverages the File System Access API with fallbacks for older systems.
• Wasm-Native: Built using dart:js_interop and package:web (No legacy dart:html).
• Pure Dart: 100% UI-agnostic. Works on Web, Mobile, Desktop, and the CLI.

Installation

Run

dart pub add file_streamer

in your project root or add:

file_streamer: ^0.1.0

to the dependencies section in your pubspec.yaml.

Setup

macOS

macOS apps require file access entitlements to read user-selected files.

Add the following to macos/Runner/DebugProfile.entitlements and macos/Runner/Release.entitlements:

<key>com.apple.security.files.user-selected.read-only</key>
<true/>

If you want to upload files, you also need to enable outgoing connections in your App Sandbox:

1. Open macos/Runner.xcworkspace in Xcode.
2. Select the Runner project in the project navigator.
3. Go to the Signing & Capabilities tab.
4. Under App Sandbox -> Network, check Outgoing Connections (Client).

Tests

Run vm-annotated tests with:

dart test

Browser tests are ran with:

dart test -p chrome