BufferTextWriter.md

TextWriter for IBufferWriter<byte>

Given an IBufferWriter<byte>, an adapter to progressively write text to it can be useful. Many APIs already accept a TextWriter to write text to. Console.Out and StreamWriter are TextWriters, for example.

The BufferTextWriter class derives from TextWriter and accepts an IBufferWriter<byte> in order to enable writing text to a byte buffer or stream.

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

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

Example

private readonly BufferTextWriter textWriter = new BufferTextWriter();

void ReadTextFromConsole(IBufferWriter<byte> byteWriter)
{
    textWriter.Initialize(byteWriter, Encoding.UTF8);
    string line;
    while ((line = Console.In.ReadLine()) != null)
    {
        textWriter.WriteLine(line);
    }
}