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prefer-bytes-builder

added in: 1.3.0
warning
Pro+

Warns when an expensive byte list operation is used.

Using lists concatenation, addAll or spread operator can significantly affect the performance. It's recommended to use a BytesBuilder instead.

info

The rule by default will trigger on every list of integers. It's up to you to scope it to files where you work with bytes.

Example​

❌ Bad:

void run() {
  List<int> buffer = Uint8List(0);
  for (var i = 0; i < 100; i++) {
    final Uint8List chunk = chunks[i];
    final List<int> intChunk = chunks[i];

    buffer = buffer + chunk; // LINT: Prefer 'BytesBuilder' to compose bytes. Try rewriting the code to use it instead.
    buffer = buffer + intChunk; // LINT: Prefer 'BytesBuilder' to compose bytes. Try rewriting the code to use it instead.
    buffer += chunk; // LINT: Prefer 'BytesBuilder' to compose bytes. Try rewriting the code to use it instead.
    buffer += intChunk; // LINT: Prefer 'BytesBuilder' to compose bytes. Try rewriting the code to use it instead.
  }
}

✅ Good:

void run() {
  final buffer = BytesBuilder();
  for (var i = 0; i < 100; i++) {
    buffer.add(chunks[i]);
  }
  buffer.toBytes();
}

Additional Resources​