[FEATURE REQ] Add helper for converting a stream to BinaryData

[m-nash]

Library name

Azure.Core

Please describe the feature.

BinaryData.FromStream does a copy so its is faster to use the ReadOnlyMemory overload instead.

MemoryStream stream = GetWrittenStream();
BinaryData data = new BinaryData(stream.GetBuffer().AsMemory(0, (int)stream.Position))

The issue with the above code is stream position is a long and memory wants an int. We need to check for this like this.

MemoryStream stream = GetWrittenStream();
BinaryData data = stream.Position > int.MaxValue
                    ? BinaryData.FromStream(stream)
                    : new BinaryData(stream.GetBuffer().AsMemory(0, (int)stream.Position));

BinaryData.FromStream currently will throw if length is too long if we want to throw or we can do the following

MemoryStream stream = GetWrittenStream();
BinaryData data = stream.Position > int.MaxValue
                    ? new BinaryData(stream.ToArray())
                    : new BinaryData(stream.GetBuffer().AsMemory(0, (int)stream.Position));

The reason for the else is we only want to take the perf hit when the length is larger that max int.

The question is should we provide a helper for this to avoid accidently doing a sub optimal thing.

[annelo-msft]

Why not make a PR to BinaryData in the dotnet/runtime repo?