asio: Start sending response header when write_head is called

examples/asio-sv.cc

@@ -70,6 +70,17 @@ int main(int argc, char *argv[]) {
       res.write_head(200);
       res.end("under construction!");
     });
+    server.handle("/push", [](const request &req, const response &res) {
+      boost::system::error_code ec;
+      auto push = res.push(ec, "GET", "/push/1");
+      if (!ec) {
+        push->write_head(200);
+        push->end("server push FTW!");
+      }
+
+      res.write_head(200);
+      res.end("you'll receive server push!");
+    });
     server.listen("*", port);
 
   } catch (std::exception &e) {

src/asio_common.cc

@@ -63,6 +63,11 @@ read_cb string_reader(std::string data) {
   };
 }
 
+read_cb deferred_reader() {
+  return [](uint8_t *buf, size_t len,
+            uint32_t *data_flags) { return NGHTTP2_ERR_DEFERRED; };
+}
+
 template <typename F, typename... T>
 std::shared_ptr<Defer<F, T...>> defer_shared(F &&f, T &&... t) {
   return std::make_shared<Defer<F, T...>>(std::forward<F>(f),

src/asio_common.h

@@ -37,9 +37,12 @@ namespace nghttp2 {
 
 namespace asio_http2 {
 
+boost::system::error_code make_error_code(nghttp2_error ev);
+
 read_cb string_reader(std::string data);
 
-boost::system::error_code make_error_code(nghttp2_error ev);
+// Returns read_cb, which just returns NGHTTP2_ERR_DEFERRED
+read_cb deferred_reader();
 
 template <typename InputIt>
 void split_path(uri_ref &dst, InputIt first, InputIt last) {

src/asio_server_http2_handler.cc

@@ -204,8 +204,7 @@ int on_frame_send_callback(nghttp2_session *session, const nghttp2_frame *frame,
   }
 
   auto &res = strm->response().impl();
-  res.push_promise_sent(true);
-  res.start_response();
+  res.push_promise_sent();
 
   return 0;
 }

src/asio_server_response.cc

@@ -64,8 +64,6 @@ boost::asio::io_service &response::io_service() const {
   return impl_->io_service();
 }
 
-bool response::started() const { return impl_->started(); }
-
 response_impl &response::impl() const { return *impl_; }
 
 } // namespace server

src/asio_server_response_impl.cc

@@ -33,33 +33,58 @@ namespace asio_http2 {
 namespace server {
 
 response_impl::response_impl()
-    : strm_(nullptr), status_code_(200), started_(false), pushed_(false),
+    : strm_(nullptr), read_cb_(deferred_reader()), status_code_(200),
+      state_(response_state::INITIAL), pushed_(false),
       push_promise_sent_(false) {}
 
 unsigned int response_impl::status_code() const { return status_code_; }
 
 void response_impl::write_head(unsigned int status_code, header_map h) {
+  if (state_ != response_state::INITIAL) {
+    return;
+  }
+
   status_code_ = status_code;
   header_ = std::move(h);
-}
 
-void response_impl::end(std::string data) {
-  if (started_) {
+  state_ = response_state::HEADER_DONE;
+
+  if (pushed_ && !push_promise_sent_) {
     return;
   }
 
+  start_response();
+}
+
+void response_impl::end(std::string data) {
   end(string_reader(std::move(data)));
 }
 
 void response_impl::end(read_cb cb) {
-  if (started_) {
+  if (state_ == response_state::BODY_STARTED) {
     return;
   }
 
   read_cb_ = std::move(cb);
-  started_ = true;
 
-  start_response();
+  if (state_ == response_state::INITIAL) {
+    write_head(status_code_);
+  } else {
+    // read_cb is changed, start writing in case it is deferred.
+    auto handler = strm_->handler();
+    handler->resume(*strm_);
+  }
+
+  state_ = response_state::BODY_STARTED;
+}
+
+void response_impl::start_response() {
+  auto handler = strm_->handler();
+
+  if (handler->start_response(*strm_) != 0) {
+    handler->stream_error(strm_->get_stream_id(), NGHTTP2_INTERNAL_ERROR);
+    return;
+  }
 }
 
 void response_impl::on_close(close_cb cb) { close_cb_ = std::move(cb); }
@@ -75,19 +100,6 @@ void response_impl::cancel(uint32_t error_code) {
   handler->stream_error(strm_->get_stream_id(), error_code);
 }
 
-void response_impl::start_response() {
-  if (!started_ || (pushed_ && !push_promise_sent_)) {
-    return;
-  }
-
-  auto handler = strm_->handler();
-
-  if (handler->start_response(*strm_) != 0) {
-    handler->stream_error(strm_->get_stream_id(), NGHTTP2_INTERNAL_ERROR);
-    return;
-  }
-}
-
 response *response_impl::push(boost::system::error_code &ec, std::string method,
                               std::string raw_path_query, header_map h) const {
   auto handler = strm_->handler();
@@ -104,11 +116,18 @@ boost::asio::io_service &response_impl::io_service() {
   return strm_->handler()->io_service();
 }
 
-bool response_impl::started() const { return started_; }
-
 void response_impl::pushed(bool f) { pushed_ = f; }
 
-void response_impl::push_promise_sent(bool f) { push_promise_sent_ = f; }
+void response_impl::push_promise_sent() {
+  if (push_promise_sent_) {
+    return;
+  }
+  push_promise_sent_ = true;
+  if (state_ == response_state::INITIAL) {
+    return;
+  }
+  start_response();
+}
 
 const header_map &response_impl::header() const { return header_; }
 

src/asio_server_response_impl.h

@@ -35,6 +35,14 @@ namespace server {
 
 class stream;
 
+enum class response_state {
+  INITIAL,
+  // response_impl::write_head() was called
+  HEADER_DONE,
+  // response_impl::end() was called
+  BODY_STARTED,
+};
+
 class response_impl {
 public:
   response_impl();
@@ -55,9 +63,8 @@ public:
 
   unsigned int status_code() const;
   const header_map &header() const;
-  bool started() const;
   void pushed(bool f);
-  void push_promise_sent(bool f);
+  void push_promise_sent();
   void stream(class stream *s);
   read_cb::result_type call_read(uint8_t *data, std::size_t len,
                                  uint32_t *data_flags);
@@ -69,8 +76,7 @@ private:
   read_cb read_cb_;
   close_cb close_cb_;
   unsigned int status_code_;
-  // true if response started (end() is called)
-  bool started_;
+  response_state state_;
   // true if this is pushed stream's response
   bool pushed_;
   // true if PUSH_PROMISE is sent if this is response of a pushed

src/includes/nghttp2/asio_http2_server.h

@@ -97,9 +97,6 @@ public:
   // Returns status code.
   unsigned int status_code() const;
 
-  // Returns true if response has been started.
-  bool started() const;
-
   // Returns boost::asio::io_service this response is running on.
   boost::asio::io_service &io_service() const;