code: func (b *Buffer) Bytes() []byte {
  	switch {
  	case b.written >= b.size && b.writeCursor == 0:
  		return b.data
  	case b.written > b.size:
  		out := make([]byte, b.size)
  		copy(out, b.data[b.writeCursor:])
  		copy(out[b.size-b.writeCursor:], b.data[:b.writeCursor])
  		return out
  	default:
  		return b.data[:b.writeCursor]
  	}
  }
docs: // Bytes provides a slice of the bytes written. This
  // slice should not be written to.