Add RequestHeader.VisitAllInOrder

header.go

@@ -778,6 +778,8 @@ func (h *RequestHeader) VisitAllCookie(f func(key, value []byte)) {
 //
 // f must not retain references to key and/or value after returning.
 // Copy key and/or value contents before returning if you need retaining them.
+//
+// To get the headers in order they were received use VisitAllInOrder.
 func (h *RequestHeader) VisitAll(f func(key, value []byte)) {
 	h.parseRawHeaders()
 	host := h.Host()
@@ -807,6 +809,25 @@ func (h *RequestHeader) VisitAll(f func(key, value []byte)) {
 	}
 }
 
+// VisitAllInOrder calls f for each header in the order they were received.
+//
+// f must not retain references to key and/or value after returning.
+// Copy key and/or value contents before returning if you need retaining them.
+//
+// This function is slightly slower than VisitAll because it has to reparse the
+// raw headers to get the order.
+func (h *RequestHeader) VisitAllInOrder(f func(key, value []byte)) {
+	h.parseRawHeaders()
+	var s headerScanner
+	s.b = h.rawHeaders
+	s.disableNormalizing = h.disableNormalizing
+	for s.next() {
+		if len(s.key) > 0 {
+			f(s.key, s.value)
+		}
+	}
+}
+
 // Del deletes header with the given key.
 func (h *ResponseHeader) Del(key string) {
 	k := getHeaderKeyBytes(&h.bufKV, key, h.disableNormalizing)

header_test.go

@@ -1277,6 +1277,47 @@ func TestRequestHeaderVisitAll(t *testing.T) {
 	}
 }
 
+func TestResponseHeaderVisitAllInOrder(t *testing.T) {
+	var h RequestHeader
+
+	r := bytes.NewBufferString("GET / HTTP/1.1\r\nContent-Type: aa\r\nCookie: a=b\r\nHost: example.com\r\nUser-Agent: xxx\r\n\r\n")
+	br := bufio.NewReader(r)
+	if err := h.Read(br); err != nil {
+		t.Fatalf("Unepxected error: %s", err)
+	}
+
+	if h.Len() != 4 {
+		t.Fatalf("Unexpected number of headers: %d. Expected 4", h.Len())
+	}
+
+	order := []string{
+		"Content-Type",
+		"Cookie",
+		"Host",
+		"User-Agent",
+	}
+	values := []string{
+		"aa",
+		"a=b",
+		"example.com",
+		"xxx",
+	}
+
+	h.VisitAllInOrder(func(key, value []byte) {
+		if len(order) == 0 {
+			t.Fatalf("no more headers expected, got %q", key)
+		}
+		if order[0] != string(key) {
+			t.Fatalf("expected header %q got %q", order[0], key)
+		}
+		if values[0] != string(value) {
+			t.Fatalf("expected header value %q got %q", values[0], value)
+		}
+		order = order[1:]
+		values = values[1:]
+	})
+}
+
 func TestResponseHeaderCookie(t *testing.T) {
 	var h ResponseHeader
 	var c Cookie