Decode UTF-8 from stream (can handle characters that span buffer boundary)

DecodeFromStream.cs

StringBuilder lineBuilder = new StringBuilder();

Encoding encoding = Encoding.UTF8;

// A Decoder is stateful; it remembers if it's halfway through decoding a multi-byte character.
Decoder decoder = encoding.GetDecoder();
            
byte[] buffer = new byte[10];
int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);
while (bytesRead > 0)
{
    // AF: This is a little inefficient because it winds up scanning the buffer twice, but I've not had much luck progressively scanning chunks of the buffer.
    char[] decodeBuffer = new char[decoder.GetCharCount(buffer, 0, bytesRead)];
    int charactersDecoded = decoder.GetChars(buffer, 0, bytesRead, decodeBuffer, 0);
    for (int charIndex = 0; charIndex < charactersDecoded; charIndex++)
    {
        const char CR = '\r';
        const char LF = '\n';

        char decodedCharacter = decodeBuffer[charIndex];
        switch (decodedCharacter)
        {
            case CR:
            {
                if (charIndex < charactersDecoded - 1 && decodeBuffer[charIndex + 1] == LF)
                {
                    charIndex++;

                    goto case LF;
                }

                break;
            }
            case LF:
            {
                string line = lineBuilder.ToString();
                lineBuilder.Clear();

                Console.WriteLine(line);

                break;
            }
            default:
            {
                lineBuilder.Append(decodedCharacter);

                break;
            }
        }
    }

    bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);
}

// If stream doesn't end with a line-terminator sequence, publish trailing characters as the last line.
if (lineBuilder.Length > 0)
    Console.WriteLine(lineBuilder);