examples: add http3.c, altsvc.c and http3-present.c

Closes #4221

docs/examples/Makefile.inc

@@ -35,7 +35,8 @@ check_PROGRAMS = 10-at-a-time anyauthput cookie_interface debug fileupload \
   http2-upload http2-serverpush getredirect ftpuploadfrommem               \
   ftpuploadresume sslbackend postit2-formadd multi-formadd                 \
   shared-connection-cache sftpuploadresume http2-pushinmemory parseurl     \
-  urlapi imap-authzid pop3-authzid smtp-authzid
+  urlapi imap-authzid pop3-authzid smtp-authzid http3 altsvc               \
+  http3-present
 
 # These examples require external dependencies that may not be commonly
 # available on POSIX systems, so don't bother attempting to compile them here.

docs/examples/altsvc.c

@@ -0,0 +1,56 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+/* <DESC>
+ * HTTP with Alt-Svc support
+ * </DESC>
+ */
+#include <stdio.h>
+#include <curl/curl.h>
+
+int main(void)
+{
+  CURL *curl;
+  CURLcode res;
+
+  curl = curl_easy_init();
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
+
+    /* cache the alternatives in this file */
+    curl_easy_setopt(curl, CURLOPT_ALTSVC, "altsvc.txt");
+
+    /* restrict which HTTP versions to use alternatives */
+    curl_easy_setopt(curl, CURLOPT_ALTSVC_CTRL, (long)
+                     CURLALTSVC_H1|CURLALTSVC_H2|CURLALTSVC_H3);
+
+    /* Perform the request, res will get the return code */
+    res = curl_easy_perform(curl);
+    /* Check for errors */
+    if(res != CURLE_OK)
+      fprintf(stderr, "curl_easy_perform() failed: %s\n",
+              curl_easy_strerror(res));
+
+    /* always cleanup */
+    curl_easy_cleanup(curl);
+  }
+  return 0;
+}

docs/examples/http3-present.c

@@ -0,0 +1,47 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+/* <DESC>
+ * Checks if HTTP/3 support is present in libcurl.
+ * </DESC>
+ */
+#include <stdio.h>
+#include <curl/curl.h>
+
+int main(void)
+{
+  curl_version_info_data *ver;
+
+  curl_global_init(CURL_GLOBAL_ALL);
+
+  ver = curl_version_info(CURLVERSION_NOW);
+  if(ver->features & CURL_VERSION_HTTP2)
+    printf("HTTP/2 support is present\n");
+
+  if(ver->features & CURL_VERSION_HTTP3)
+    printf("HTTP/3 support is present\n");
+
+  if(ver->features & CURL_VERSION_ALTSVC)
+    printf("Alt-svc support is present\n");
+
+  curl_global_cleanup();
+  return 0;
+}

docs/examples/http3.c

@@ -0,0 +1,54 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+/* <DESC>
+ * Very simple HTTP/3 GET
+ * </DESC>
+ */
+#include <stdio.h>
+#include <curl/curl.h>
+
+int main(void)
+{
+  CURL *curl;
+  CURLcode res;
+
+  curl = curl_easy_init();
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
+
+    /* Forcing HTTP/3 will make the connection fail if the server isn't
+       accessible over QUIC + HTTP/3 on the given host and port.
+       Consider using CURLOPT_ALTSVC instead! */
+    curl_easy_setopt(curl, CURLOPT_HTTP_VERSION, (long)CURL_HTTP_VERSION_3);
+
+    /* Perform the request, res will get the return code */
+    res = curl_easy_perform(curl);
+    /* Check for errors */
+    if(res != CURLE_OK)
+      fprintf(stderr, "curl_easy_perform() failed: %s\n",
+              curl_easy_strerror(res));
+
+    /* always cleanup */
+    curl_easy_cleanup(curl);
+  }
+  return 0;
+}