Cache elements of State

Cache the size and the do bit whenever someone asked for it. We can

probably add more:



PASS

BenchmarkStateDo-4  	100000000	        11.9 ns/op

BenchmarkStateSize-4	 5000000	       265 ns/op

ok  	github.com/miekg/coredns/middleware	2.828s



PASS

BenchmarkStateDo-4  	1000000000	         2.86 ns/op

BenchmarkStateSize-4	500000000	         3.10 ns/op

ok  	github.com/miekg/coredns/middleware	5.032s



This PR also includes some testing cleanups as well.

middleware/testing/helpers.go

@@ -3,8 +3,6 @@ package testing
 import (
 	"testing"
 
-	"github.com/miekg/coredns/middleware"
-
 	"github.com/miekg/dns"
 	"golang.org/x/net/context"
 )
@@ -199,11 +197,27 @@ func Section(t *testing.T, tc Case, sect Sect, rr []dns.RR) bool {
 	return true
 }
 
-func ErrorHandler() middleware.Handler {
-	return middleware.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+func ErrorHandler() Handler {
+	return HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
 		m := new(dns.Msg)
 		m.SetRcode(r, dns.RcodeServerFailure)
 		w.WriteMsg(m)
 		return dns.RcodeServerFailure, nil
 	})
 }
+
+// Copied here to prevent an import cycle.
+type (
+	// HandlerFunc is a convenience type like dns.HandlerFunc, except
+	// ServeDNS returns an rcode and an error.
+	HandlerFunc func(context.Context, dns.ResponseWriter, *dns.Msg) (int, error)
+
+	Handler interface {
+		ServeDNS(context.Context, dns.ResponseWriter, *dns.Msg) (int, error)
+	}
+)
+
+// ServeDNS implements the Handler interface.
+func (f HandlerFunc) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	return f(ctx, w, r)
+}

middleware/testing/responsewriter.go

@@ -0,0 +1,28 @@
+package testing
+
+import (
+	"net"
+
+	"github.com/miekg/dns"
+)
+
+type ResponseWriter struct{}
+
+func (t *ResponseWriter) LocalAddr() net.Addr {
+	ip := net.ParseIP("127.0.0.1")
+	port := 53
+	return &net.UDPAddr{IP: ip, Port: port, Zone: ""}
+}
+
+func (t *ResponseWriter) RemoteAddr() net.Addr {
+	ip := net.ParseIP("10.240.0.1")
+	port := 40212
+	return &net.UDPAddr{IP: ip, Port: port, Zone: ""}
+}
+
+func (t *ResponseWriter) WriteMsg(m *dns.Msg) error     { return nil }
+func (t *ResponseWriter) Write(buf []byte) (int, error) { return len(buf), nil }
+func (t *ResponseWriter) Close() error                  { return nil }
+func (t *ResponseWriter) TsigStatus() error             { return nil }
+func (t *ResponseWriter) TsigTimersOnly(bool)           { return }
+func (t *ResponseWriter) Hijack()                       { return }