NewScanWriter returns a new ScanWriter.

ScanWriterMaxBufferSize is the maximum size of the ScanWriter buffer.

ByteCounter is a simple io.Writer that counts the number of bytes written to it, to be used in conjunction with io.MultiWriter / io.TeeReader.

ScanWriter is an io.WriteCloser wrapper for bufio.Scanner.

CallbackFn is a function that takes a string as an argument and returns nothing.