Hello encode/decode. (#132)

hello.go

@@ -0,0 +1,27 @@
+package dilithium
+
+import (
+	"github.com/openziti/dilithium/util"
+	"github.com/pkg/errors"
+)
+
+type hello struct {
+	version uint32
+}
+
+func encodeHello(hello hello, data []byte) (n uint32, err error) {
+	dataSize := len(data)
+	if dataSize < 4 {
+		return 0, errors.Errorf("hello too large [%d < 4]", dataSize)
+	}
+	util.WriteUint32(data, hello.version)
+	return 4, nil
+}
+
+func decodeHello(data []byte) (hello, uint32, error) {
+	dataSize := len(data)
+	if dataSize < 5 {
+		return hello{}, 0, errors.Errorf("short hello decode buffer [%d < 4]", dataSize)
+	}
+	return hello{util.ReadUint32(data)}, 4, nil
+}