You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: dns.go
    path of file: ./repos/sliver/implant/vendor/github.com/miekg/dns
    
    the code of the file until where you have to start completion: package dns

import (
	"encoding/hex"
	"strconv"
)

const (
	year68     = 1 << 31 // For RFC1982 (Serial Arithmetic) calculations in 32 bits.
	defaultTtl = 3600    // Default internal TTL.

    
func (rr *RFC3597) ToRFC3597(r RR) error {
	buf := make([]byte, Len(r))
	headerEnd, off, err := packRR(r, buf, 0, compressionMap{}, false)
	if err != nil {
		return err
	}
	buf = buf[:off]

	*rr = RFC3597{Hdr: *r.Header()}
	rr.Hdr.Rdlength = uint16(off - headerEnd)

	if noRdata(rr.Hdr) {
		return nil
	}

	_, err = rr.unpack(buf, headerEnd)
	return err
}