[dart-misc] 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' via Dart Misc]

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.

Post by 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
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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

Post by 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
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For more ways to connect visit https://www.dartlang.org/community
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[Denis Portnov]

Florian, Istvan, Than your for your comments.
Btw, is it correct 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