Pass a *C between middleware and router

Previously, the middleware stack passed the router a C, but this was
both odd semantically (a pattern which mutated the environment might see
a *different* environment) and bad for perf: it cost us an allocation.

Now we only pass around *C's internally.

Importantly ("importantly"), this gets us down to 0 allocations for the
static routing case, and one allocation (the URLParams map) for the
normal routing case.

web/middleware.go

@@ -19,7 +19,11 @@ type mStack struct {
 	lock   sync.Mutex
 	stack  []mLayer
 	pool   chan *cStack
-	router Handler
+	router internalRouter
+}
+
+type internalRouter interface {
+	route(*C, http.ResponseWriter, *http.Request)
 }
 
 /*
@@ -93,7 +97,7 @@ func (m *mStack) newStack() *cStack {
 	router := m.router
 
 	cs.m = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		router.ServeHTTPC(cs.C, w, r)
+		router.route(&cs.C, w, r)
 	})
 	for i := len(m.stack) - 1; i >= 0; i-- {
 		cs.m = m.stack[i].fn(&cs.C, cs.m)

web/middleware_test.go

@@ -7,14 +7,20 @@ import (
 	"time"
 )
 
+type iRouter func(*C, http.ResponseWriter, *http.Request)
+
+func (i iRouter) route(c *C, w http.ResponseWriter, r *http.Request) {
+	i(c, w, r)
+}
+
 func makeStack(ch chan string) *mStack {
-	router := func(c C, w http.ResponseWriter, r *http.Request) {
+	router := func(c *C, w http.ResponseWriter, r *http.Request) {
 		ch <- "router"
 	}
 	return &mStack{
 		stack:  make([]mLayer, 0),
 		pool:   make(chan *cStack, mPoolSize),
-		router: HandlerFunc(router),
+		router: iRouter(router),
 	}
 }
 
@@ -202,7 +208,7 @@ func TestInvalidation(t *testing.T) {
 }
 
 func TestContext(t *testing.T) {
-	router := func(c C, w http.ResponseWriter, r *http.Request) {
+	router := func(c *C, w http.ResponseWriter, r *http.Request) {
 		if c.Env["reqID"].(int) != 2 {
 			t.Error("Request id was not 2 :(")
 		}
@@ -210,7 +216,7 @@ func TestContext(t *testing.T) {
 	st := mStack{
 		stack:  make([]mLayer, 0),
 		pool:   make(chan *cStack, mPoolSize),
-		router: HandlerFunc(router),
+		router: iRouter(router),
 	}
 	st.Use(func(c *C, h http.Handler) http.Handler {
 		fn := func(w http.ResponseWriter, r *http.Request) {

web/mux.go

@@ -68,7 +68,7 @@ func New() *Mux {
 			notFound: parseHandler(http.NotFound),
 		},
 	}
-	mux.mStack.router = HandlerFunc(mux.router.route)
+	mux.mStack.router = &mux.router
 	return &mux
 }
 

web/router.go

@@ -219,18 +219,18 @@ func (rt *router) Compile() {
 	rt.setMachine(&sm)
 }
 
-func (rt *router) route(c C, w http.ResponseWriter, r *http.Request) {
+func (rt *router) route(c *C, w http.ResponseWriter, r *http.Request) {
 	if rt.machine == nil {
 		rt.Compile()
 	}
 
-	methods, ok := rt.getMachine().route(&c, w, r)
+	methods, ok := rt.getMachine().route(c, w, r)
 	if ok {
 		return
 	}
 
 	if methods == 0 {
-		rt.notFound.ServeHTTPC(c, w, r)
+		rt.notFound.ServeHTTPC(*c, w, r)
 		return
 	}
 
@@ -249,7 +249,7 @@ func (rt *router) route(c C, w http.ResponseWriter, r *http.Request) {
 	} else {
 		c.Env[ValidMethodsKey] = methodsList
 	}
-	rt.notFound.ServeHTTPC(c, w, r)
+	rt.notFound.ServeHTTPC(*c, w, r)
 }
 
 func (rt *router) handleUntyped(p interface{}, m method, h interface{}) {

web/router_test.go

@@ -46,7 +46,7 @@ func TestMethods(t *testing.T) {
 	for _, method := range methods {
 		r, _ := http.NewRequest(method, "/", nil)
 		w := httptest.NewRecorder()
-		rt.route(C{}, w, r)
+		rt.route(&C{}, w, r)
 		select {
 		case val := <-ch:
 			if val != method {
@@ -119,7 +119,7 @@ func TestHandlerTypes(t *testing.T) {
 	for route, response := range testHandlerTable {
 		r, _ := http.NewRequest("GET", route, nil)
 		w := httptest.NewRecorder()
-		rt.route(C{}, w, r)
+		rt.route(&C{}, w, r)
 		select {
 		case resp := <-ch:
 			if resp != response {
@@ -209,7 +209,7 @@ func TestRouteSelection(t *testing.T) {
 		for counter, n = range test.results {
 			r, _ := http.NewRequest("GET", test.key, nil)
 			w := httptest.NewRecorder()
-			rt.route(C{}, w, r)
+			rt.route(&C{}, w, r)
 			actual := <-ichan
 			if n != actual {
 				t.Errorf("Expected %q @ %d to be %d, got %d",
@@ -225,7 +225,7 @@ func TestNotFound(t *testing.T) {
 
 	r, _ := http.NewRequest("post", "/", nil)
 	w := httptest.NewRecorder()
-	rt.route(C{}, w, r)
+	rt.route(&C{}, w, r)
 	if w.Code != 404 {
 		t.Errorf("Expected 404, got %d", w.Code)
 	}
@@ -236,7 +236,7 @@ func TestNotFound(t *testing.T) {
 
 	r, _ = http.NewRequest("POST", "/", nil)
 	w = httptest.NewRecorder()
-	rt.route(C{}, w, r)
+	rt.route(&C{}, w, r)
 	if w.Code != http.StatusTeapot {
 		t.Errorf("Expected a teapot, got %d", w.Code)
 	}
@@ -253,7 +253,7 @@ func TestPrefix(t *testing.T) {
 
 	r, _ := http.NewRequest("GET", "/hello/world", nil)
 	w := httptest.NewRecorder()
-	rt.route(C{}, w, r)
+	rt.route(&C{}, w, r)
 	select {
 	case val := <-ch:
 		if val != "/hello/world" {
@@ -302,7 +302,7 @@ func TestValidMethods(t *testing.T) {
 
 	for path, eMethods := range validMethodsTable {
 		r, _ := http.NewRequest("BOGUS", path, nil)
-		rt.route(C{}, httptest.NewRecorder(), r)
+		rt.route(&C{}, httptest.NewRecorder(), r)
 		aMethods := <-ch
 		if !reflect.DeepEqual(eMethods, aMethods) {
 			t.Errorf("For %q, expected %v, got %v", path, eMethods,