func (b *Reader) Reset(r io.Reader) {
	// If a Reader r is passed to NewReader, NewReader will return r.
	// Different layers of code may do that, and then later pass r
	// to Reset. Avoid infinite recursion in that case.
	if b == r {
		return
	}
	if b.buf == nil {
		b.buf = make([]byte, defaultBufSize)
	}
	b.reset(b.buf, r)
}

func (b *Reader) reset(buf []byte, r io.Reader) {
	*b = Reader{