asio: Add server::response::write_trailer()

examples/asio-sv.cc

@@ -101,6 +101,30 @@ int main(int argc, char *argv[]) {
         res.end("finally!\n");
       });
     });
+    server.handle("/trailer", [](const request &req, const response &res) {
+      // send trailer part.
+      res.write_head(200, {{"trailers", {"digest"}}});
+
+      std::string body = "nghttp2 FTW!\n";
+      auto left = std::make_shared<size_t>(body.size());
+
+      res.end([&res, body, left](uint8_t *dst, std::size_t len,
+                                 uint32_t *data_flags) {
+        auto n = std::min(len, *left);
+        std::copy_n(body.c_str() + (body.size() - *left), n, dst);
+        *left -= n;
+        if (*left == 0) {
+          *data_flags |=
+              NGHTTP2_DATA_FLAG_EOF | NGHTTP2_DATA_FLAG_NO_END_STREAM;
+          // RFC 3230 Instance Digests in HTTP.  The digest value is
+          // SHA-256 message digest of body.
+          res.write_trailer(
+              {{"digest",
+                {"SHA-256=qqXqskW7F3ueBSvmZRCiSwl2ym4HRO0M/pvQCBlSDis="}}});
+        }
+        return n;
+      });
+    });
 
     if (argc >= 6) {
       boost::asio::ssl::context tls(boost::asio::ssl::context::sslv23);

src/asio_server_http2_handler.cc

@@ -359,6 +359,27 @@ int http2_handler::start_response(stream &strm) {
   return 0;
 }
 
+int http2_handler::submit_trailer(stream &strm, header_map h) {
+  int rv;
+  auto nva = std::vector<nghttp2_nv>();
+  nva.reserve(h.size());
+  for (auto &hd : h) {
+    nva.push_back(nghttp2::http2::make_nv(hd.first, hd.second.value,
+                                          hd.second.sensitive));
+  }
+
+  rv = nghttp2_submit_trailer(session_, strm.get_stream_id(), nva.data(),
+                              nva.size());
+
+  if (rv != 0) {
+    return -1;
+  }
+
+  signal_write();
+
+  return 0;
+}
+
 void http2_handler::enter_callback() {
   assert(!inside_callback_);
   inside_callback_ = true;

src/asio_server_http2_handler.h

@@ -70,6 +70,8 @@ public:
 
   int start_response(stream &s);
 
+  int submit_trailer(stream &s, header_map h);
+
   void stream_error(int32_t stream_id, uint32_t error_code);
 
   void initiate_write();

src/asio_server_response.cc

@@ -46,6 +46,10 @@ void response::end(std::string data) const { impl_->end(std::move(data)); }
 
 void response::end(generator_cb cb) const { impl_->end(std::move(cb)); }
 
+void response::write_trailer(header_map h) const {
+  impl_->write_trailer(std::move(h));
+}
+
 void response::on_close(close_cb cb) const { impl_->on_close(std::move(cb)); }
 
 void response::cancel(uint32_t error_code) const { impl_->cancel(error_code); }

src/asio_server_response_impl.cc

@@ -81,6 +81,11 @@ void response_impl::end(generator_cb cb) {
   state_ = response_state::BODY_STARTED;
 }
 
+void response_impl::write_trailer(header_map h) {
+  auto handler = strm_->handler();
+  handler->submit_trailer(*strm_, std::move(h));
+}
+
 void response_impl::start_response() {
   auto handler = strm_->handler();
 

src/asio_server_response_impl.h

@@ -49,6 +49,7 @@ public:
   void write_head(unsigned int status_code, header_map h = {});
   void end(std::string data = "");
   void end(generator_cb cb);
+  void write_trailer(header_map h);
   void on_close(close_cb cb);
   void resume();
 

src/includes/nghttp2/asio_http2_server.h

@@ -81,6 +81,11 @@ public:
   // call of end() is allowed.
   void end(generator_cb cb) const;
 
+  // Write trailer part.  This must be called after setting both
+  // NGHTTP2_DATA_FLAG_EOF and NGHTTP2_DATA_FLAG_NO_END_STREAM set in
+  // *data_flag parameter in generator_cb passed to end() function.
+  void write_trailer(header_map h) const;
+
   // Sets callback which is invoked when this request and response are
   // finished.  After the invocation of this callback, the application
   // must not access request and response object.

src/template.h

@@ -76,6 +76,10 @@ template <typename F, typename... T> Defer<F, T...> defer(F &&f, T &&... t) {
   return Defer<F, T...>(std::forward<F>(f), std::forward<T>(t)...);
 }
 
+template <typename T, typename F> bool test_flags(T t, F flags) {
+  return (t & flags) == flags;
+}
+
 } // namespace nghttp2
 
 #endif // TEMPLATE_H