Add altsvc support

This allows the connection to discover http/3 ports.

CMakeLists.txt

@@ -26,7 +26,7 @@ option(USE_BUNDLED_SPDLOG "Use the bundled version of spdlog." ${HUNTER_ENABLED}
 
 
 project(coeurl
-	VERSION 0.2.1
+	VERSION 0.3.0
 	DESCRIPTION "Simple library to do http requests asynchronously via CURL in C++."
 	HOMEPAGE_URL "https://nheko.im/nheko-reborn/cocurl")
 

include/coeurl/client.hpp

@@ -27,7 +27,7 @@ struct SockInfo;
 
 //! Global information, common to all connections
 struct Client {
-    //! construct a new client
+    //! construct a new client. For http/3 support, set the alt_svc_cache_path as well.
     Client();
     /// @brief cleans up a client
     /// Implicitly closes the connection and blocks until all of them exited.
@@ -151,6 +151,12 @@ struct Client {
     //! Default is 8.
     void maximum_connections_per_host(long count);
 
+    //! Cache alternative service entries. This allows automatically switching to http/3.
+    //! Usually you provide a path in `~/.cache` or similar.
+    void alt_svc_cache_path(const std::string &path) { alt_svc_cache_path_ = path; }
+    //! Where alternate svc entries are cached. Usually in `~/.cache`.
+    const std::string &alt_svc_cache_path() const { return alt_svc_cache_path_; }
+
   private:
     // Call this to run the event loop. Will block until the client is shutdown.
     void run();
@@ -196,6 +202,8 @@ struct Client {
 
     std::thread bg_thread;
 
+    std::string alt_svc_cache_path_;
+
     friend Request;
 };
 } // namespace coeurl

lib/request.cpp

@@ -125,6 +125,11 @@ Request::Request(Client *client, Method m, std::string url__) : url_(std::move(u
     curl_easy_setopt(this->easy, CURLOPT_XFERINFOFUNCTION, prog_cb);
     curl_easy_setopt(this->easy, CURLOPT_XFERINFODATA, this);
     curl_easy_setopt(this->easy, CURLOPT_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);
+
+    // enable altsvc support, which allows us to switch to http3
+    curl_easy_setopt(this->easy, CURLOPT_ALTSVC_CTRL, CURLALTSVC_H1|CURLALTSVC_H2|CURLALTSVC_H3);
+    curl_easy_setopt(this->easy, CURLOPT_ALTSVC, client->alt_svc_cache_path().c_str());
+
     // default to all supported encodings
     curl_easy_setopt(this->easy, CURLOPT_ACCEPT_ENCODING, "");
 

meson.build

 project('coeurl', 'cpp',
-  version : '0.2.1',
+  version : '0.3.0',
   license : 'MIT',
   meson_version : '>=0.54',
   default_options : ['warning_level=3', 'cpp_std=c++17']