Describe the bug

The public static unsafe T Read<T>(this Stream stream) extension method makes the assumption that the Read(Span<byte>) must read exactly length bytes.
If it returns less than that, it throws with the message that the stream did not contain enough data.

The only time this assumption is correct is when the stream is a MemoryStream.
All other Stream implementations are free to return fewer bytes than requested and commonly do so.

Steps to reproduce

Have a stream like

class CustomStream : Stream
{
    private ReadOnlyMemory<byte> _bufferedBytes;

    public int Read(Span<byte> buffer)
    {
        if (!_bufferedBytes.IsEmpty)
        {
            int toCopy = Math.Min(_bufferedBytes.Length, buffer.Length);
            _bufferedBytes.Span.Slice(0, toCopy).CopyTo(buffer);
            _bufferedBytes = _bufferedBytes.Slice(toCopy);
            return toCopy;
        }

        return GetMoreBytes(buffer);
    }
}

And call

stream.Read<int>();

You may hit an exception telling you that the stream ended even though more data is actually available, you just happened to read while the buffer had fewer than 4 bytes in it.

Expected behavior

The Read helper would loop until either receiving length bytes, or until the Read returned 0 indicating the end of the stream.

IDE and version

VS 2022 Preview

Nuget packages

• CommunityToolkit.Common
• CommunityToolkit.Diagnostics
• CommunityToolkit.HighPerformance
• CommunityToolkit.Mvvm (aka MVVM Toolkit)

Additional context

I'm not actually using this library, just saw the code as someone mentioned it in dotnet/runtime.

Help us help you

No, just wanted to report this