options: API for meta-data about easy options

 const struct curl_easyoption *curl_easy_option_by_name(const char *name);

 const struct curl_easyoption *curl_easy_option_by_id (CURLoption id);

 const struct curl_easyoption *
 curl_easy_option_next(const struct curl_easyoption *prev);

The purpose is to provide detailed enough information to allow for
example libcurl bindings to get option information at run-time about
what easy options that exist and what arguments they expect.

Assisted-by: Jeroen Ooms
Closes #5365

1 files changed, 73 insertions, 0 deletions

diff --git a/lib/easygetopt.c b/lib/easygetopt.c
new file mode 100644
index 000000000..8cfd49977
--- /dev/null
+++ b/lib/easygetopt.c
@@ -0,0 +1,73 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ | |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             ___|___/|_| ______|
+ *
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel.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.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+#include "strcase.h"
+#include "easyoptions.h"
+
+/* Lookups easy options at runtime */
+static struct curl_easyoption *lookup(const char *name, CURLoption id)
+{
+  DEBUGASSERT(name || id);
+  DEBUGASSERT(!Curl_easyopts_check());
+  if(name || id) {
+    struct curl_easyoption *o = &Curl_easyopts[0];
+    do {
+      if(name) {
+        if(strcasecompare(o->name, name))
+          return o;
+      }
+      else {
+        if((o->id == id) && !(o->flags & CURLOT_FLAG_ALIAS))
+          /* don't match alias options */
+          return o;
+      }
+      o++;
+    } while(o->name);
+  }
+  return NULL;
+}
+
+const struct curl_easyoption *curl_easy_option_by_name(const char *name)
+{
+  return lookup(name, 0);
+}
+
+const struct curl_easyoption *curl_easy_option_by_id(CURLoption id)
+{
+  return lookup(NULL, id);
+}
+
+/* Iterates over available options */
+const struct curl_easyoption *
+curl_easy_option_next(const struct curl_easyoption *prev)
+{
+  if(prev && prev->name) {
+    prev++;
+    if(prev->name)
+      return prev;
+  }
+  else if(!prev)
+    return &Curl_easyopts[0];
+  return NULL;
+}
+