SequenceTextReader.md

TextReader for ReadOnlySequence<byte>

Given a ReadOnlySequence<byte>, an adapter to progressively read it as text can be useful. Many APIs already accept a TextReader to read text. Console.In and StreamReader are TextReaders, for example.

The SequenceTextReader class derives from TextReader and accepts a ReadOnlySequence<byte> in order to enable reading text from a byte sequence.

You can also use the ReadOnlySequence<byte>.AsStream() extension method to create a Stream and pass that as an argument when constructing a new StreamReader, but creating a StreamReader allocates a couple of large byte[] and char[] arrays which make this an expensive approach, particularly when you need to read from many unique ReadOnlySequence<byte> instances and thus have to repeatedly create a new StreamReader and its own buffers each time.

SequenceTextReader avoids these costs by optimizing for reading directly from the ReadOnlySequence<byte> (avoiding the Stream intermediate adapter) and by allowing the same SequenceTextReader instance to be assigned different ReadOnlySequence<byte> over time, allowing reuse of the buffers it uses internally during the decoding process.

Example

private readonly SequenceTextReader sequenceReader = new SequenceTextReader();

void PrintTextToConsole(ReadOnlySequence<byte> sequence)
{
    sequenceReader.Initialize(sequence, Encoding.UTF8);
    string line;
    while ((line = sequenceReader.ReadLine()) != null)
    {
        Console.WriteLine(line);
    }
}