1 files changed, 60 insertions, 0 deletions
diff --git a/rfc1035label/label.go b/rfc1035label/label.go
new file mode 100644
index 0000000..c63b4af
--- /dev/null
+++ b/rfc1035label/label.go
@@ -0,0 +1,60 @@
+package rfc1035label
+
+import (
+	"fmt"
+	"strings"
+)
+
+// This implements the compression from RFC 1035, section 4.1.4
+// https://tools.ietf.org/html/rfc1035
+
+// LabelsFromBytes decodes a serialized stream and returns a list of labels
+func LabelsFromBytes(buf []byte) ([]string, error) {
+	var (
+		pos     = 0
+		domains = make([]string, 0)
+		label   = ""
+	)
+	for {
+		if pos >= len(buf) {
+			return domains, nil
+		}
+		length := int(buf[pos])
+		pos++
+		if length == 0 {
+			domains = append(domains, label)
+			label = ""
+		}
+		if len(buf)-pos < length {
+			return nil, fmt.Errorf("DomainNamesFromBytes: invalid short label length")
+		}
+		if label != "" {
+			label += "."
+		}
+		label += string(buf[pos : pos+length])
+		pos += length
+	}
+}
+
+// LabelToBytes encodes a label and returns a serialized stream of bytes
+func LabelToBytes(label string) []byte {
+	var encodedLabel []byte
+	if len(label) == 0 {
+		return []byte{0}
+	}
+	for _, part := range strings.Split(label, ".") {
+		encodedLabel = append(encodedLabel, byte(len(part)))
+		encodedLabel = append(encodedLabel, []byte(part)...)
+	}
+	return append(encodedLabel, 0)
+}
+
+// LabelsToBytes encodes a list of labels and returns a serialized stream of
+// bytes
+func LabelsToBytes(labels []string) []byte {
+	var encodedLabels []byte
+	for _, label := range labels {
+		encodedLabels = append(encodedLabels, LabelToBytes(label)...)
+	}
+	return encodedLabels
+}