webclient improvements

Highlights:

* TLS support (a hook to allow users to provide TLS implementation)
* ability to add extra request headers
* ability to use PUT method
* ability to report http status
* error handling improvements

Proposed on the ML while ago:
https://www.mail-archive.com/dev@nuttx.apache.org/msg03803.html

The original API is kept for now.
I plan to remove them after adapting the existing users.
(examples in this repo)

include/netutils/webclient.h

@@ -103,6 +103,140 @@
 typedef void (*wget_callback_t)(FAR char **buffer, int offset,
                                 int datend, FAR int *buflen, FAR void *arg);
 
+/* webclient_sink_callback_t: callback to consume data
+ *
+ * Same as wget_callback_t, but allowed to fail.
+ *
+ * Input Parameters:
+ *   Same as wget_callback_t
+ *
+ * Return value:
+ *   0 on success.
+ *   A negative errno on error.
+ */
+
+typedef CODE int (*webclient_sink_callback_t)(FAR char **buffer, int offset,
+                                              int datend, FAR int *buflen,
+                                              FAR void *arg);
+
+/* webclient_body_callback_t: a callback to provide request body
+ *
+ * This callback can be called multiple times to provide
+ * webclient_context::bodylen bytes of the data.
+ * It's the responsibility of this callback to maintain the current
+ * "offset" of the data. (similarly to fread(3))
+ *
+ * An implementation of this callback should perform either of
+ * the followings:
+ *
+ * - fill the buffer (specified by buffer and *sizep) with the data
+ * - update *datap with a buffer filled with the data
+ *
+ * Either ways, it should update *sizep to the size of the data.
+ *
+ * A short result is allowed. In that case, this callback will be called
+ * again to provide the remaining data.
+ *
+ * Input Parameters:
+ *   buffer - The buffer to fill.
+ *   sizep  - The size of buffer/data in bytes.
+ *   datap  - The data to return.
+ *   ctx    - The value of webclient_context::body_callback_arg.
+ *
+ * Return value:
+ *   0 on success.
+ *   A negative errno on error.
+ */
+
+typedef CODE int (*webclient_body_callback_t)(
+    FAR void *buffer,
+    FAR size_t *sizep,
+    FAR const void * FAR *datap,
+    FAR void *ctx);
+
+struct webclient_tls_connection;
+
+struct webclient_tls_ops
+{
+  CODE int (*connect)(FAR void *ctx,
+                      FAR const char *hostname, FAR const char *port,
+                      unsigned int timeout_second,
+                      FAR struct webclient_tls_connection **connp);
+  CODE ssize_t (*send)(FAR void *ctx,
+                       FAR struct webclient_tls_connection *conn,
+                       FAR const void *buf, size_t len);
+  CODE ssize_t (*recv)(FAR void *ctx,
+                       FAR struct webclient_tls_connection *conn,
+                       FAR void *buf, size_t len);
+  CODE int (*close)(FAR void *ctx,
+                    FAR struct webclient_tls_connection *conn);
+};
+
+struct webclient_context
+{
+  /* request parameters
+   *
+   *   method       - HTTP method like "GET", "POST".
+   *                  The default value is "GET".
+   *   url          - A pointer to a string containing the full URL.
+   *                  (e.g., http://www.nutt.org/index.html, or
+   *                   http://192.168.23.1:80/index.html)
+   *   headers      - An array of pointers to the extra headers.
+   *   nheaders     - The number of elements in the "headers" array.
+   *   bodylen      - The size of the request body.
+   */
+
+  FAR const char *method;
+  FAR const char *url;
+  FAR const char * FAR const *headers;
+  unsigned int nheaders;
+  size_t bodylen;
+
+  /* other parameters
+   *
+   *   buffer            - A user provided buffer to receive the file data
+   *                       (also used for the outgoing GET request)
+   *                       It should be large enough to hold the whole
+   *                       request header. It should also be large enough
+   *                       to hold the whole response header.
+   *   buflen            - The size of the user provided buffer
+   *   sink_callback     - As data is obtained from the host, this function
+   *                       is to dispose of each block of file data as it is
+   *                       received.
+   *   callback          - a compat version of sink_callback.
+   *   sink_callback_arg - User argument passed to callback.
+   *   body_callback     - A callback function to provide the request body.
+   *   body_callback_arg - User argument passed to body_callback.
+   *   tls_ops           - A vector to implement TLS operations.
+   *                       NULL means no https support.
+   *   tls_ctx           - A user pointer to be passed to tls_ops as it is.
+   */
+
+  FAR char *buffer;
+  int buflen;
+  wget_callback_t callback;
+  webclient_sink_callback_t sink_callback;
+  FAR void *sink_callback_arg;
+  webclient_body_callback_t body_callback;
+  FAR void *body_callback_arg;
+  FAR const struct webclient_tls_ops *tls_ops;
+  FAR void *tls_ctx;
+
+  /* results
+   *
+   *   http_status     - HTTP status code
+   *   http_reason     - A buffer to store HTTP reason phrase.
+   *                     If NULL, the reason phrase will be discarded.
+   *   http_reason_len - The size of the http_reason buffer
+   *                     A reason phrase longer than the buffer size
+   *                     will be silently truncated.
+   */
+
+  unsigned int http_status;
+  FAR char *http_reason;
+  size_t http_reason_len;
+};
+
 /****************************************************************************
  * Public Function Prototypes
  ****************************************************************************/
@@ -153,6 +287,12 @@ int wget(FAR const char *url, FAR char *buffer, int buflen,
 int wget_post(FAR const char *url, FAR const char *posts, FAR char *buffer,
               int buflen, wget_callback_t callback, FAR void *arg);
 
+void webclient_set_defaults(FAR struct webclient_context *ctx);
+int webclient_perform(FAR struct webclient_context *ctx);
+void webclient_set_static_body(FAR struct webclient_context *ctx,
+                               FAR const void *body,
+                               size_t bodylen);
+
 #undef EXTERN
 #ifdef __cplusplus
 }