bufwriter

type Writer interface {
	io.Writer

	// Len returns the number of buffered bytes.
	Len() int

	// Flush writes any buffered data to the underlying writer.
	Flush() error

	// Reset discards the unwritten data, clears the error and sets a new destination.
	Reset(io.Writer)

	// Free frees the writer, releases its internal resources.
	Free()
}