WIP: autopath as middleware (#859)

autopath as middleware

middleware/autopath/nonwriter.go

@@ -0,0 +1,22 @@
+package autopath
+
+import (
+	"github.com/miekg/dns"
+)
+
+// NonWriter is a type of ResponseWriter that captures the message, but never writes to the client.
+type NonWriter struct {
+	dns.ResponseWriter
+	Msg *dns.Msg
+}
+
+// NewNonWriter makes and returns a new NonWriter.
+func NewNonWriter(w dns.ResponseWriter) *NonWriter { return &NonWriter{ResponseWriter: w} }
+
+// WriteMsg records the message, but doesn't write it itself.
+func (r *NonWriter) WriteMsg(res *dns.Msg) error {
+	r.Msg = res
+	return nil
+}
+
+func (r *NonWriter) Write(buf []byte) (int, error) { return len(buf), nil }