Byte array representation in Dart 2

[Denis Portnov]

Hi all, 

What is idiomatic way in Dart 2 for representing byte array? What type to use?

I see that io, convert, crypto etc. all require or produce byte arrays as List<int>

It's not very convenient for library author as it requires either to check/truncate individual ints from List, or use Uint8List.fromList() everywhere.

Flutter explicitly goes with Uint8List https://docs.flutter.io/flutter/widgets/Image/Image.memory.html

So let's say I'm doing library for IP address, UUID, hash, or any structure with underlying byte array. 

Is it fine to have this

  class IPAddress {
    IPAddress.fromBytes(Uint8List bytes) {}
 
    Uint8List get bytes;
  }

  class SomeBinaryEncoder extends Converter<Uint8List, Uint8List> {

    Uint8List convert(Uint8List input) {}

 
  }

Thanks

Denis

[Florian Loitsch]

Yes.

It's perfectly fine to stick to Uint8Lists if that's what you use internally, and if you expect most users of your API to be comfortable with it.

dart:io, ... would probably now switch to explicit `Uint8List` as well.

Alternatively, you can take `List<int>` and create a function `ensureUint8List` that does an `is` check and only converts the list if it isn't already one.

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[Istvan Soos]

Both should work in most cases just fine, however I have a slight
preference on the least restrictive inputs. E.g. when a method expects
bytes as input, I'd prefer to have it as List<int>, but when it
returns these values, it is could be nicer if it returns them as
Uint8List, if/when the implementation will use that anyway.

As Florian suggested, you can easily convert it to Uint8List
internally if that is important for the implementation logic.

Also, for some byte-concatenation tasks, CombinedListView from
package:collection can be useful.

Cheers,
Istvan

[Denis Portnov]

Florian, Istvan, Than your for your comments. 

Btw, is that the right assumption that on  VM/dart-js level typed_data collections are more optimal in terms of processing compared to List<int>?

Thanks
Denis