convert method

Implementation

@override
Uint8List convert(String s) {
  var result = Uint8List(64);
  var resultLength = 0;
  var lineNumber = 0;

  for (var line in s.split('\n')) {
    lineNumber++;

    // Remove possible line prefix (like "0000000: ")
    final match = _prefixRegExp.matchAsPrefix(line);
    if (match != null) {
      line = line.substring(match.end);
    }

    int? firstGroupLength;

    // Parse each group of hexadecimal digits
    while (true) {
      final match = _hexRegExp.matchAsPrefix(line);
      if (match == null) break;

      final group = match.group(1)!;
      line = line.substring(match.end);

      // Validate even length
      if (group.length.isOdd) {
        throw ArgumentError(
          "Error at line $lineNumber: invalid group of hexadecimal digits (non-even length): '$group'",
        );
      }

      // Record the length of the first group for comparison
      if (firstGroupLength == null) {
        firstGroupLength = group.length;
      } else if (group.length > firstGroupLength) {
        // Longer than the first group → stop parsing hex for this line
        break;
      }

      // Parse each byte from the hex string
      for (var i = 0; i < group.length; i += 2) {
        final byteString = group.substring(i, i + 2);
        int byte;
        try {
          byte = int.parse(byteString, radix: 16);
        } catch (_) {
          throw ArgumentError.value(
            "Error at line $lineNumber: '$byteString' is not valid hex",
          );
        }

        // Expand buffer if needed
        if (resultLength == result.lengthInBytes) {
          final oldResult = result;
          result = Uint8List(resultLength * 2);
          result.setAll(0, oldResult);
        }

        // Append parsed byte
        result[resultLength++] = byte;
      }
    }
  }

  return Uint8List.view(result.buffer, 0, resultLength);
}