dnscontrol/pkg/txtutil/txtutil.go

package txtutil

import (
	"github.com/StackExchange/dnscontrol/v3/models"
)

// SplitSingleLongTxt finds TXT records with a single long string and splits it
// into 255-octet chunks. This is used by providers that, when a user specifies
// one long TXT string, split it into smaller strings behind the scenes.
// Typically this replaces the TXTMulti capability.
func SplitSingleLongTxt(records []*models.RecordConfig) {
	for _, rc := range records {
		if rc.HasFormatIdenticalToTXT() {
			s := rc.TxtStrings[0]
			if len(rc.TxtStrings) == 1 && len(s) > 255 {
				rc.SetTargetTXTs(splitChunks(s, 255))
			}
		}
	}
}

func splitChunks(buf string, lim int) []string {
	var chunk string
	chunks := make([]string, 0, len(buf)/lim+1)
	for len(buf) >= lim {
		chunk, buf = buf[:lim], buf[lim:]
		chunks = append(chunks, chunk)
	}
	if len(buf) > 0 {
		chunks = append(chunks, buf[:])
	}
	return chunks
}