Decode sksl.json files generated by flutter run --profile --cache-sksl

decode_flutter_sksl.dart

import 'dart:convert';
import 'dart:io';

void main(List<String> args) async {
  if (args.isEmpty || args.length > 1) {
    print('The program decodes flutter sksl.json cache files\n');
    print('Usage: dart main.dart <skslJsonFile>');
    exit(1);
  }

  final String inputFileName = args[0];
  if (!File(inputFileName).existsSync()) {
    print('Error: file $inputFileName does not exists');
    exit(1);
  }

  final String content = File(inputFileName).readAsStringSync();
  final Map<String, dynamic> skslJson = jsonDecode(content);
  print(skslJson['platform']);
  print(skslJson['name']);
  print(skslJson['engineRevision']);

  final Map<String, dynamic> skslData = skslJson['data'];
  List<int> outputBuffer = [];
  for (String encodedValue in skslData.values) {
    final String stripped = encodedValue.substring(16);
    final Iterable<int> decoded =
        base64Decode(stripped).where((element) => element != 0);
    outputBuffer.addAll(decoded);
  }

  final String outputFilename = inputFileName + '.glsl';
  File(outputFilename).writeAsBytesSync(outputBuffer);
}