How to hash a large video file in Dart

main.dart

import 'dart:io';
import 'dart:convert';
import 'dart:crypto';
import 'package:file/file.dart';
import 'package:stream_transform/stream_transform.dart';

///a function that takes a File object and a chosen hashing algorithm (e.g., SHA-256)
Future<String> hashFile(File file, Digest digest, int chunkSize) async {
   final sink = AccumulatorSink<List<int>>();
  await file.openRead().pipe(chunkStream(file, chunkSize)).pipe(transform(digest));
  final bytes = await sink.value;
  return convert.base64Encode(bytes); // Base64 encoding for String output
}

///a helper function to split the file into smaller chunks:
Stream<List<int>> chunkStream(File file, int chunkSize) async* {
  final bytes = await file.readAsBytes();
  for (var i = 0; i < bytes.length; i += chunkSize) {
    final chunk = bytes.sublist(i, min(i + chunkSize, bytes.length));
    yield chunk;
  }
}


Future<void> main() async {
  final file = File('path/to/your/video.mp4');  // Replace with your file path
  final digest = SHA256();
  final chunkSize = 1024 * 1024; // 1 MB chunks (adjust as needed)

  try {
    final hash = await hashFile(file, digest, chunkSize);
    print('Hash of the video: $hash');
  } on Exception catch (e) {
    print('Error hashing file: $e');
  }
}

pubspec.yaml

dependencies:
  crypto: ^3.0.1
  file: ^0.6.6
  stream_transform: ^2.2.0