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

3 files changed, 119 insertions, 40 deletions

diff --git a/include/curl/Makefile.am b/include/curl/Makefile.am
index a31f61b10..db96ace89 100644
--- a/include/curl/Makefile.am
+++ b/include/curl/Makefile.am
@@ -5,7 +5,7 @@
 #                            | (__| |_| |  _ <| |___
 #                             \___|\___/|_| \_\_____|
 #
-# Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+# Copyright (C) 1998 - 2020, 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
@@ -21,7 +21,7 @@
 ###########################################################################
 pkginclude_HEADERS = \
   curl.h curlver.h easy.h mprintf.h stdcheaders.h multi.h \
-  typecheck-gcc.h system.h urlapi.h
+  typecheck-gcc.h system.h urlapi.h options.h
 
 pkgincludedir= $(includedir)/curl
 
diff --git a/include/curl/curl.h b/include/curl/curl.h
index 2366ef3c7..32d9bd4a7 100644
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -1002,17 +1002,27 @@ typedef enum {
 
 #define CURLOPT(na,t,nu) na = t + nu
 
-/* handy aliases that make no run-time difference */
-#define CURLOPTTYPE_STRINGPOINT  CURLOPTTYPE_OBJECTPOINT
+/* CURLOPT aliases that make no run-time difference */
+
+/* 'char *' argument to a string with a trailing zero */
+#define CURLOPTTYPE_STRINGPOINT CURLOPTTYPE_OBJECTPOINT
+
+/* 'struct curl_slist *' argument */
 #define CURLOPTTYPE_SLISTPOINT  CURLOPTTYPE_OBJECTPOINT
 
+/* 'void *' argument passed untouched to callback */
+#define CURLOPTTYPE_CBPOINT     CURLOPTTYPE_OBJECTPOINT
+
+/* 'long' argument with a set of values/bitmask */
+#define CURLOPTTYPE_VALUES      CURLOPTTYPE_LONG
+
 /*
  * All CURLOPT_* values.
  */
 
 typedef enum {
   /* This is the FILE * or void * the regular output should be written to. */
-  CURLOPT(CURLOPT_WRITEDATA, CURLOPTTYPE_OBJECTPOINT, 1),
+  CURLOPT(CURLOPT_WRITEDATA, CURLOPTTYPE_CBPOINT, 1),
 
   /* The full URL to get/put */
   CURLOPT(CURLOPT_URL, CURLOPTTYPE_STRINGPOINT, 2),
@@ -1035,7 +1045,7 @@ typedef enum {
   /* not used */
 
   /* Specified file stream to upload from (use as input): */
-  CURLOPT(CURLOPT_READDATA, CURLOPTTYPE_OBJECTPOINT, 9),
+  CURLOPT(CURLOPT_READDATA, CURLOPTTYPE_CBPOINT, 9),
 
   /* Buffer to receive error messages in, must be at least CURL_ERROR_SIZE
    * bytes big. */
@@ -1120,7 +1130,7 @@ typedef enum {
 
   /* send FILE * or void * to store headers to, if you use a callback it
      is simply passed to the callback unmodified */
-  CURLOPT(CURLOPT_HEADERDATA, CURLOPTTYPE_OBJECTPOINT, 29),
+  CURLOPT(CURLOPT_HEADERDATA, CURLOPTTYPE_CBPOINT, 29),
 
   /* point to a file to read the initial cookies from, also enables
      "cookie awareness" */
@@ -1128,10 +1138,10 @@ typedef enum {
 
   /* What version to specifically try to use.
      See CURL_SSLVERSION defines below. */
-  CURLOPT(CURLOPT_SSLVERSION, CURLOPTTYPE_LONG, 32),
+  CURLOPT(CURLOPT_SSLVERSION, CURLOPTTYPE_VALUES, 32),
 
   /* What kind of HTTP time condition to use, see defines */
-  CURLOPT(CURLOPT_TIMECONDITION, CURLOPTTYPE_LONG, 33),
+  CURLOPT(CURLOPT_TIMECONDITION, CURLOPTTYPE_VALUES, 33),
 
   /* Time to use with the above condition. Specified in number of seconds
      since 1 Jan 1970 */
@@ -1185,7 +1195,7 @@ typedef enum {
 
   /* Specify whether to read the user+password from the .netrc or the URL.
    * This must be one of the CURL_NETRC_* enums below. */
-  CURLOPT(CURLOPT_NETRC, CURLOPTTYPE_LONG, 51),
+  CURLOPT(CURLOPT_NETRC, CURLOPTTYPE_VALUES, 51),
 
   /* use Location: Luke! */
   CURLOPT(CURLOPT_FOLLOWLOCATION, CURLOPTTYPE_LONG, 52),
@@ -1206,8 +1216,8 @@ typedef enum {
 
   /* Data passed to the CURLOPT_PROGRESSFUNCTION and CURLOPT_XFERINFOFUNCTION
      callbacks */
-  CURLOPT(CURLOPT_PROGRESSDATA, CURLOPTTYPE_OBJECTPOINT, 57),
-#define CURLOPT_XFERINFODATA CURLOPT_PROGRESSDATA
+  CURLOPT(CURLOPT_XFERINFODATA, CURLOPTTYPE_CBPOINT, 57),
+#define CURLOPT_PROGRESSDATA CURLOPT_XFERINFODATA
 
   /* We want the referrer field set automatically when following locations */
   CURLOPT(CURLOPT_AUTOREFERER, CURLOPTTYPE_LONG, 58),
@@ -1302,7 +1312,7 @@ typedef enum {
 
   /* Specify which HTTP version to use! This must be set to one of the
      CURL_HTTP_VERSION* enums set below. */
-  CURLOPT(CURLOPT_HTTP_VERSION, CURLOPTTYPE_LONG, 84),
+  CURLOPT(CURLOPT_HTTP_VERSION, CURLOPTTYPE_VALUES, 84),
 
   /* Specifically switch on or off the FTP engine's use of the EPSV command. By
      default, that one will always be attempted before the more traditional
@@ -1340,7 +1350,7 @@ typedef enum {
   CURLOPT(CURLOPT_DEBUGFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 94),
 
   /* set the data for the debug function */
-  CURLOPT(CURLOPT_DEBUGDATA, CURLOPTTYPE_OBJECTPOINT, 95),
+  CURLOPT(CURLOPT_DEBUGDATA, CURLOPTTYPE_CBPOINT, 95),
 
   /* mark this as start of a cookie session */
   CURLOPT(CURLOPT_COOKIESESSION, CURLOPTTYPE_LONG, 96),
@@ -1363,7 +1373,7 @@ typedef enum {
   /* indicates type of proxy. accepted values are CURLPROXY_HTTP (default),
      CURLPROXY_HTTPS, CURLPROXY_SOCKS4, CURLPROXY_SOCKS4A and
      CURLPROXY_SOCKS5. */
-  CURLOPT(CURLOPT_PROXYTYPE, CURLOPTTYPE_LONG, 101),
+  CURLOPT(CURLOPT_PROXYTYPE, CURLOPTTYPE_VALUES, 101),
 
   /* Set the Accept-Encoding string. Use this to tell a server you would like
      the response to be compressed. Before 7.21.6, this was known as
@@ -1389,7 +1399,7 @@ typedef enum {
   /* Set this to a bitmask value to enable the particular authentications
      methods you like. Use this in combination with CURLOPT_USERPWD.
      Note that setting multiple bits may cause extra network round-trips. */
-  CURLOPT(CURLOPT_HTTPAUTH, CURLOPTTYPE_LONG, 107),
+  CURLOPT(CURLOPT_HTTPAUTH, CURLOPTTYPE_VALUES, 107),
 
   /* Set the ssl context callback function, currently only for OpenSSL or
      WolfSSL ssl_ctx, or mbedTLS mbedtls_ssl_config in the second argument.
@@ -1398,7 +1408,7 @@ typedef enum {
 
   /* Set the userdata for the ssl context callback function's third
      argument */
-  CURLOPT(CURLOPT_SSL_CTX_DATA, CURLOPTTYPE_OBJECTPOINT, 109),
+  CURLOPT(CURLOPT_SSL_CTX_DATA, CURLOPTTYPE_CBPOINT, 109),
 
   /* FTP Option that causes missing dirs to be created on the remote server.
      In 7.19.4 we introduced the convenience enums for this option using the
@@ -1409,7 +1419,7 @@ typedef enum {
   /* Set this to a bitmask value to enable the particular authentications
      methods you like. Use this in combination with CURLOPT_PROXYUSERPWD.
      Note that setting multiple bits may cause extra network round-trips. */
-  CURLOPT(CURLOPT_PROXYAUTH, CURLOPTTYPE_LONG, 111),
+  CURLOPT(CURLOPT_PROXYAUTH, CURLOPTTYPE_VALUES, 111),
 
   /* FTP option that changes the timeout, in seconds, associated with
      getting a response.  This is different from transfer timeout time and
@@ -1421,7 +1431,7 @@ typedef enum {
   /* Set this option to one of the CURL_IPRESOLVE_* defines (see below) to
      tell libcurl to resolve names to those IP versions only. This only has
      affect on systems with support for more than one, i.e IPv4 _and_ IPv6. */
-  CURLOPT(CURLOPT_IPRESOLVE, CURLOPTTYPE_LONG, 113),
+  CURLOPT(CURLOPT_IPRESOLVE, CURLOPTTYPE_VALUES, 113),
 
   /* Set this option to limit the size of a file that will be downloaded from
      an HTTP or FTP server.
@@ -1456,7 +1466,7 @@ typedef enum {
      CURLUSESSL_CONTROL - SSL for the control connection or fail
      CURLUSESSL_ALL     - SSL for all communication or fail
   */
-  CURLOPT(CURLOPT_USE_SSL, CURLOPTTYPE_LONG, 119),
+  CURLOPT(CURLOPT_USE_SSL, CURLOPTTYPE_VALUES, 119),
 
   /* The _LARGE version of the standard POSTFIELDSIZE option */
   CURLOPT(CURLOPT_POSTFIELDSIZE_LARGE, CURLOPTTYPE_OFF_T, 120),
@@ -1482,10 +1492,10 @@ typedef enum {
      CURLFTPAUTH_SSL     - try "AUTH SSL" first, then TLS
      CURLFTPAUTH_TLS     - try "AUTH TLS" first, then SSL
   */
-  CURLOPT(CURLOPT_FTPSSLAUTH, CURLOPTTYPE_LONG, 129),
+  CURLOPT(CURLOPT_FTPSSLAUTH, CURLOPTTYPE_VALUES, 129),
 
   CURLOPT(CURLOPT_IOCTLFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 130),
-  CURLOPT(CURLOPT_IOCTLDATA, CURLOPTTYPE_OBJECTPOINT, 131),
+  CURLOPT(CURLOPT_IOCTLDATA, CURLOPTTYPE_CBPOINT, 131),
 
   /* 132 OBSOLETE. Gone in 7.16.0 */
   /* 133 OBSOLETE. Gone in 7.16.0 */
@@ -1508,7 +1518,7 @@ typedef enum {
 
   /* Select "file method" to use when doing FTP, see the curl_ftpmethod
      above. */
-  CURLOPT(CURLOPT_FTP_FILEMETHOD, CURLOPTTYPE_LONG, 138),
+  CURLOPT(CURLOPT_FTP_FILEMETHOD, CURLOPTTYPE_VALUES, 138),
 
   /* Local port number to bind the socket to */
   CURLOPT(CURLOPT_LOCALPORT, CURLOPTTYPE_LONG, 139),
@@ -1545,14 +1555,14 @@ typedef enum {
 
   /* callback function for setting socket options */
   CURLOPT(CURLOPT_SOCKOPTFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 148),
-  CURLOPT(CURLOPT_SOCKOPTDATA, CURLOPTTYPE_OBJECTPOINT, 149),
+  CURLOPT(CURLOPT_SOCKOPTDATA, CURLOPTTYPE_CBPOINT, 149),
 
   /* set to 0 to disable session ID re-use for this transfer, default is
      enabled (== 1) */
   CURLOPT(CURLOPT_SSL_SESSIONID_CACHE, CURLOPTTYPE_LONG, 150),
 
   /* allowed SSH authentication methods */
-  CURLOPT(CURLOPT_SSH_AUTH_TYPES, CURLOPTTYPE_LONG, 151),
+  CURLOPT(CURLOPT_SSH_AUTH_TYPES, CURLOPTTYPE_VALUES, 151),
 
   /* Used by scp/sftp to do public/private key authentication */
   CURLOPT(CURLOPT_SSH_PUBLIC_KEYFILE, CURLOPTTYPE_STRINGPOINT, 152),
@@ -1577,7 +1587,7 @@ typedef enum {
 
   /* Set the behaviour of POST when redirecting. Values must be set to one
      of CURL_REDIR* defines below. This used to be called CURLOPT_POST301 */
-  CURLOPT(CURLOPT_POSTREDIR, CURLOPTTYPE_LONG, 161),
+  CURLOPT(CURLOPT_POSTREDIR, CURLOPTTYPE_VALUES, 161),
 
   /* used by scp/sftp to verify the host's public key */
   CURLOPT(CURLOPT_SSH_HOST_PUBLIC_KEY_MD5, CURLOPTTYPE_STRINGPOINT, 162),
@@ -1587,7 +1597,7 @@ typedef enum {
      CURL_SOCKET_BAD.  The callback should have type
      curl_opensocket_callback */
   CURLOPT(CURLOPT_OPENSOCKETFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 163),
-  CURLOPT(CURLOPT_OPENSOCKETDATA, CURLOPTTYPE_OBJECTPOINT, 164),
+  CURLOPT(CURLOPT_OPENSOCKETDATA, CURLOPTTYPE_CBPOINT, 164),
 
   /* POST volatile input fields. */
   CURLOPT(CURLOPT_COPYPOSTFIELDS, CURLOPTTYPE_OBJECTPOINT, 165),
@@ -1597,7 +1607,7 @@ typedef enum {
 
   /* Callback function for seeking in the input stream */
   CURLOPT(CURLOPT_SEEKFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 167),
-  CURLOPT(CURLOPT_SEEKDATA, CURLOPTTYPE_OBJECTPOINT, 168),
+  CURLOPT(CURLOPT_SEEKDATA, CURLOPTTYPE_CBPOINT, 168),
 
   /* CRL file */
   CURLOPT(CURLOPT_CRLFILE, CURLOPTTYPE_STRINGPOINT, 169),
@@ -1658,7 +1668,7 @@ typedef enum {
   CURLOPT(CURLOPT_SSH_KEYFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 184),
 
   /* set the SSH host key callback custom pointer */
-  CURLOPT(CURLOPT_SSH_KEYDATA, CURLOPTTYPE_OBJECTPOINT, 185),
+  CURLOPT(CURLOPT_SSH_KEYDATA, CURLOPTTYPE_CBPOINT, 185),
 
   /* set the SMTP mail originator */
   CURLOPT(CURLOPT_MAIL_FROM, CURLOPTTYPE_STRINGPOINT, 186),
@@ -1670,7 +1680,7 @@ typedef enum {
   CURLOPT(CURLOPT_FTP_USE_PRET, CURLOPTTYPE_LONG, 188),
 
   /* RTSP request method (OPTIONS, SETUP, PLAY, etc...) */
-  CURLOPT(CURLOPT_RTSP_REQUEST, CURLOPTTYPE_LONG, 189),
+  CURLOPT(CURLOPT_RTSP_REQUEST, CURLOPTTYPE_VALUES, 189),
 
   /* The RTSP session identifier */
   CURLOPT(CURLOPT_RTSP_SESSION_ID, CURLOPTTYPE_STRINGPOINT, 190),
@@ -1688,7 +1698,7 @@ typedef enum {
   CURLOPT(CURLOPT_RTSP_SERVER_CSEQ, CURLOPTTYPE_LONG, 194),
 
   /* The stream to pass to INTERLEAVEFUNCTION. */
-  CURLOPT(CURLOPT_INTERLEAVEDATA, CURLOPTTYPE_OBJECTPOINT, 195),
+  CURLOPT(CURLOPT_INTERLEAVEDATA, CURLOPTTYPE_CBPOINT, 195),
 
   /* Let the application define a custom write method for RTP data */
   CURLOPT(CURLOPT_INTERLEAVEFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 196),
@@ -1708,10 +1718,10 @@ typedef enum {
   CURLOPT(CURLOPT_FNMATCH_FUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 200),
 
   /* Let the application define custom chunk data pointer */
-  CURLOPT(CURLOPT_CHUNK_DATA, CURLOPTTYPE_OBJECTPOINT, 201),
+  CURLOPT(CURLOPT_CHUNK_DATA, CURLOPTTYPE_CBPOINT, 201),
 
   /* FNMATCH_FUNCTION user pointer */
-  CURLOPT(CURLOPT_FNMATCH_DATA, CURLOPTTYPE_OBJECTPOINT, 202),
+  CURLOPT(CURLOPT_FNMATCH_DATA, CURLOPTTYPE_CBPOINT, 202),
 
   /* send linked-list of name:port:address sets */
   CURLOPT(CURLOPT_RESOLVE, CURLOPTTYPE_SLISTPOINT, 203),
@@ -1740,10 +1750,10 @@ typedef enum {
   /* Callback function for closing socket (instead of close(2)). The callback
      should have type curl_closesocket_callback */
   CURLOPT(CURLOPT_CLOSESOCKETFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 208),
-  CURLOPT(CURLOPT_CLOSESOCKETDATA, CURLOPTTYPE_OBJECTPOINT, 209),
+  CURLOPT(CURLOPT_CLOSESOCKETDATA, CURLOPTTYPE_CBPOINT, 209),
 
   /* allow GSSAPI credential delegation */
-  CURLOPT(CURLOPT_GSSAPI_DELEGATION, CURLOPTTYPE_LONG, 210),
+  CURLOPT(CURLOPT_GSSAPI_DELEGATION, CURLOPTTYPE_VALUES, 210),
 
   /* Set the name servers to use for DNS resolution */
   CURLOPT(CURLOPT_DNS_SERVERS, CURLOPTTYPE_STRINGPOINT, 211),
@@ -1760,7 +1770,7 @@ typedef enum {
   CURLOPT(CURLOPT_TCP_KEEPINTVL, CURLOPTTYPE_LONG, 215),
 
   /* Enable/disable specific SSL features with a bitmask, see CURLSSLOPT_* */
-  CURLOPT(CURLOPT_SSL_OPTIONS, CURLOPTTYPE_LONG, 216),
+  CURLOPT(CURLOPT_SSL_OPTIONS, CURLOPTTYPE_VALUES, 216),
 
   /* Set the SMTP auth originator */
   CURLOPT(CURLOPT_MAIL_AUTH, CURLOPTTYPE_STRINGPOINT, 217),
@@ -1807,7 +1817,7 @@ typedef enum {
   CURLOPT(CURLOPT_PROXYHEADER, CURLOPTTYPE_SLISTPOINT, 228),
 
   /* Pass in a bitmask of "header options" */
-  CURLOPT(CURLOPT_HEADEROPT, CURLOPTTYPE_LONG, 229),
+  CURLOPT(CURLOPT_HEADEROPT, CURLOPTTYPE_VALUES, 229),
 
   /* The public key in DER form used to validate the peer public key
      this option is used only if SSL_VERIFYPEER is true */
@@ -1879,7 +1889,7 @@ typedef enum {
 
   /* What version to specifically try to use for proxy.
      See CURL_SSLVERSION defines below. */
-  CURLOPT(CURLOPT_PROXY_SSLVERSION, CURLOPTTYPE_LONG, 250),
+  CURLOPT(CURLOPT_PROXY_SSLVERSION, CURLOPTTYPE_VALUES, 250),
 
   /* Set a username for authenticated TLS for proxy */
   CURLOPT(CURLOPT_PROXY_TLSAUTH_USERNAME, CURLOPTTYPE_STRINGPOINT, 251),
@@ -1953,7 +1963,7 @@ typedef enum {
   CURLOPT(CURLOPT_RESOLVER_START_FUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 272),
 
   /* User data to pass to the resolver start callback. */
-  CURLOPT(CURLOPT_RESOLVER_START_DATA, CURLOPTTYPE_OBJECTPOINT, 273),
+  CURLOPT(CURLOPT_RESOLVER_START_DATA, CURLOPTTYPE_CBPOINT, 273),
 
   /* send HAProxy PROXY protocol header? */
   CURLOPT(CURLOPT_HAPROXYPROTOCOL, CURLOPTTYPE_LONG, 274),
@@ -1984,7 +1994,7 @@ typedef enum {
   CURLOPT(CURLOPT_TRAILERFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 283),
 
   /* pointer to be passed to HTTP_TRAILER_FUNCTION */
-  CURLOPT(CURLOPT_TRAILERDATA, CURLOPTTYPE_OBJECTPOINT, 284),
+  CURLOPT(CURLOPT_TRAILERDATA, CURLOPTTYPE_CBPOINT, 284),
 
   /* set this to 1L to allow HTTP/0.9 responses or 0L to disallow */
   CURLOPT(CURLOPT_HTTP09_ALLOWED, CURLOPTTYPE_LONG, 285),
@@ -2948,6 +2958,7 @@ CURL_EXTERN CURLcode curl_easy_pause(CURL *handle, int bitmask);
 #include "easy.h" /* nothing in curl is fun without the easy stuff */
 #include "multi.h"
 #include "urlapi.h"
+#include "options.h"
 
 /* the typechecker doesn't work in C++ (yet) */
 #if defined(__GNUC__) && defined(__GNUC_MINOR__) && \
diff --git a/include/curl/options.h b/include/curl/options.h
new file mode 100644
index 000000000..f3bd8e191
--- /dev/null
+++ b/include/curl/options.h
@@ -0,0 +1,68 @@
+#ifndef CURLINC_OPTIONS_H
+#define CURLINC_OPTIONS_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2018 - 2020, 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.
+ *
+ ***************************************************************************/
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+
+typedef enum {
+  CURLOT_LONG,    /* long (a range of values) */
+  CURLOT_VALUES,  /*      (a defined set or bitmask) */
+  CURLOT_OFF_T,   /* curl_off_t (a range of values) */
+  CURLOT_OBJECT,  /* pointer (void *) */
+  CURLOT_STRING,  /*         (char * to zero terminated buffer) */
+  CURLOT_SLIST,   /*         (struct curl_slist *) */
+  CURLOT_CBPTR,   /*         (void * passed as-is to a callback) */
+  CURLOT_BLOB,    /* blob (struct curl_blob *) */
+  CURLOT_FUNCTION /* function pointer */
+} curl_easytype;
+
+/* Flag bits */
+
+/* "alias" means it is provided for old programs to remain functional,
+   we prefer another name */
+#define CURLOT_FLAG_ALIAS (1<<0)
+
+/* The CURLOPTTYPE_* id ranges can still be used to figure out what type/size
+   to use for curl_easy_setopt() for the given id */
+struct curl_easyoption {
+  const char *name;
+  CURLoption id;
+  curl_easytype type;
+  unsigned int flags;
+};
+
+CURL_EXTERN const struct curl_easyoption *
+curl_easy_option_by_name(const char *name);
+
+CURL_EXTERN const struct curl_easyoption *
+curl_easy_option_by_id (CURLoption id);
+
+CURL_EXTERN const struct curl_easyoption *
+curl_easy_option_next(const struct curl_easyoption *prev);
+
+#ifdef __cplusplus
+} /* end of extern "C" */
+#endif
+#endif /* CURLINC_OPTIONS_H */