Dart - Whats equivalent of C# Stream/MemoryStream and stream.WriteByte(..) for Dart

Question

Need to achieve following in dart

MemoryStream stream = new MemoryStream(288);
stream.WriteByte((byte) 13);
stream.WriteByte((byte) 12);
stream.WriteByte((byte) 10);
stream.WriteByte((byte) 8);
stream.WriteByte((byte) 6);
stream.WriteByte((byte) 9);
var result = stream.ToArray();

I am coming from C#/java background and trying to use Uint8List which is equivalent to byte[] and also more efficient than List<int>. While I can add int8 in Uint8List but Uint8List can only be initialized with fixed-length. I need something dynamic where I can just say write or add without the need of any index to add. No idea how add() of Uint8List works. Couldn't find much on the internet or in docs.

Solution

I don't believe that there is a standard equivalent. (There's a GitHub comment explaining why Uint8List requires a fixed length.)

You instead could:

• Use List<int> and convert to a Uint8List afterward.
• Create your own class that wraps a Uint8List. When extra capacity is needed, you would need to allocate a new Uint8List that has, say, double the previous size, and to copy the old elements. (This is what most other growable list implementations (e.g. C++'s std::vector) do.) Possibly there is some existing Dart package on pub.dev that already does this.
• Make a class that wraps a List<Uint8List>, adding new Uint8List members as capacity is need and concatenating them into a single Uint8List when done. There is a third-party buffer package that can do this, but I have never personally used it and can't vouch for it.

Comments

[Rohit]

Is there anything similar to Outputstream or stream to write data as we go?

[jamesdlin]

@Rohit I don't know what Outputstream is. If you're looking for something that can do efficient concatenation (like C++'s std::stringstream), I think the closest equivalent from the Dart SDK would be StringBuffer. There is a third-party buffer package that does the same thing for byte data.

[Rohit]

"Buffer package" looks promising, will give it a try. May be the thing I am looking for! Thanks

[jamesdlin]

I forgot to note that I've never used and can't vouch for the buffer package; it was just the first result when I searched for "buffer" on pub.dev.

[Rohit]

Never popped that result for me, may be I was searching different terms like "streams".

[Rohit]

Can you edit your answer with buffer package as a solution. buffer package has ByteDataWriter which does exactly what I mentioned in the code example in the question. @jamesdlin

[jamesdlin]

@Rohit Okay, done. (The other approaches I mentioned could do exactly what you mentioned in your code example too. ;) )