ReadOnlySequence<char> conversion from ReadOnlySequence<byte>? - system.io.pipelines

Question

I'm trying to use System.IO.Pipelines to parse large text files.
But I can't find no conversion function from ReadOnlySequence to ReadOnlySequence. For example like MemoryMarshal.Cast<byte,char>.
IMHO it is pretty useless having a generic ReadOnlySequence<T> if there is only one particular type (byte) applicable.
static async Task ReadPipeAsync(PipeReader reader, IStringValueFactory factory)
{
while (true)
{
ReadResult result = await reader.ReadAsync();
ReadOnlySequence<byte> buffer = result.Buffer;
//ReadOnlySequence<char> chars = buffer.CastTo<char>(); ???
}
}

Answer 1

You would have to write a conversion operator to achieve this cast. You cannot cast it explicitly. Be aware that a char[] is two bytes, so you need to choose your encoding algorithm.
IMHO it is pretty useless having a generic ReadOnlySequence<T> if
there is only one particular type (byte) applicable.
While it's true that System.IO.Pipelines will only give you a ReadOnlySequence<byte> because of the fact that a PipeReader is attached to a Stream which is just a stream of bytes, there are other use cases for a ReadOnlySequence<T> eg,
ReadOnlySequence<char> roChars = new ReadOnlySequence<char>("some chars".ToCharArray());
ReadOnlySequence<string> roStrings = new ReadOnlySequence<string>(new string[] { "string1", "string2", "Another String" });
Your conversion operator would have similar logic to the below, but you would set your encoding appropriately.
static void Main(string[] args)
{
// create a 64k Readonly sequence of random bytes
var ros = new ReadOnlySequence<byte>(GenerateRandomBytes(64000));
//Optionally extract the section of the ReadOnlySequence we are interested in
var mySlice = ros.Slice(22222, 55555);
char[] charArray;
// Check if the slice is a single segment - not really necessary
// included for explanation only
if(mySlice.IsSingleSegment)
{
charArray = Encoding.ASCII.GetString(mySlice.FirstSpan).ToCharArray();
}
else
// Could only do this and always assume multiple spans
// which is highly likley for a PipeReader stream
{
Span<byte> theSpan = new byte[ros.Length];
mySlice.CopyTo(theSpan);
// ASCII Encoding - one byte of span = 2 bytes of char
charArray = Encoding.ASCII.GetString(theSpan).ToCharArray();
}
// Convert the char array back to a ReadOnlySegment<char>
var rosChar = new ReadOnlySequence<char>(charArray);
}
public static byte[] GenerateRandomBytes(int length)
{
// Create a buffer
byte[] randBytes;
if (length >= 1)
randBytes = new byte[length];
else
randBytes = new byte[1];
// Create a new RNGCryptoServiceProvider.
System.Security.Cryptography.RNGCryptoServiceProvider rand =
new System.Security.Cryptography.RNGCryptoServiceProvider();
// Fill the buffer with random bytes.
rand.GetBytes(randBytes);
// return the bytes.
return randBytes;
}