nanocoap: allow to define CoAP resources as XFA

sys/include/net/nanocoap.h

@@ -90,6 +90,7 @@
 #include "bitfield.h"
 #include "byteorder.h"
 #include "iolist.h"
+#include "macros/utils.h"
 #include "net/coap.h"
 #else
 #include "coap.h"
@@ -102,6 +103,10 @@
 typedef void sock_udp_ep_t;
 #endif
 
+#if defined(MODULE_NANOCOAP_RESOURCES)
+#include "xfa.h"
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -402,15 +407,29 @@ typedef struct {
     uint8_t *opt;                   /**< Pointer to the placed option       */
 } coap_block_slicer_t;
 
+#if defined(MODULE_NANOCOAP_RESOURCES) || DOXYGEN
+/**
+ * @brief   CoAP XFA resource entry
+ *
+ * @param name  internal name of the resource entry, must be unique
+ */
+#define NANOCOAP_RESOURCE(name) \
+    XFA_CONST(coap_resources_xfa, 0) coap_resource_t CONCAT(coap_resource_, name) =
+#else
 /**
  * @brief   Global CoAP resource list
+ * @deprecated Use @ref NANOCOAP_RESOURCE instead.
+ *             The function will be removed after the 2024.01 release.
  */
 extern const coap_resource_t coap_resources[];
 
 /**
  * @brief   Number of entries in global CoAP resource list
+ * @deprecated Use @ref NANOCOAP_RESOURCE instead.
+ *             The function will be removed after the 2024.01 release.
  */
 extern const unsigned coap_resources_numof;
+#endif
 
 /**
  * @name    Functions -- Header Read/Write
@@ -2048,6 +2067,13 @@ extern ssize_t coap_well_known_core_default_handler(coap_pkt_t *pkt, \
                                                     coap_request_ctx_t *context);
 /**@}*/
 
+/**
+ * @brief   Respond to `/.well-known/core` to list all resources on the server
+ */
+#ifndef CONFIG_NANOCOAP_SERVER_WELL_KNOWN_CORE
+#define CONFIG_NANOCOAP_SERVER_WELL_KNOWN_CORE (1)
+#endif
+
 /**
  * @brief   Checks if a CoAP resource path matches a given URI
  *

sys/include/net/nanocoap_sock.h

@@ -22,17 +22,23 @@
  *
  * ## Server Operation ##
  *
- * See the nanocoap_server example, which is built on the nanocoap_server()
- * function. A server must define an array of coap_resource_t resources for
- * which it responds. See the declarations of `coap_resources` and
- * `coap_resources_numof`. The array contents must be ordered by the resource
- * path, specifically the ASCII encoding of the path characters (digit and
- * capital precede lower case). Also see _Server path matching_ in the base
- * [nanocoap](group__net__nanocoap.html) documentation.
+ * See the nanocoap_server example, which is built on the `nanocoap_server()`
+ * function. A server must define CoAP resources for which it responds.
+ *
+ * Each @ref coap_resource_t is added to the XFA with NANOCOAP_RESOURCE(name)
+ * followed by the declaration of the CoAP resource, e.g.:
+ *
+ * ```C
+ * NANOCOAP_RESOURCE(board) {
+ *   .path = "/board", .methods = COAP_GET, .handler = _board_handler,
+ * };
+ * ```
  *
  * nanocoap itself provides the COAP_WELL_KNOWN_CORE_DEFAULT_HANDLER entry for
  * `/.well-known/core`.
  *
+ * To use the CoAP resource XFA, enable the `nanocoap_resources` module.
+ *
  * ### Handler functions ###
  *
  * For each resource, you must implement a ::coap_handler_t handler function.

sys/net/application_layer/nanocoap/nanocoap.c

@@ -41,6 +41,24 @@
 #define COAP_RST                (3)
 /** @} */
 
+#ifdef MODULE_NANOCOAP_RESOURCES
+/**
+ * @brief   CoAP resources XFA
+ */
+XFA_INIT_CONST(coap_resource_t, coap_resources_xfa);
+
+/**
+ * @brief   Add well-known .core handler
+ */
+#if CONFIG_NANOCOAP_SERVER_WELL_KNOWN_CORE
+NANOCOAP_RESOURCE(well_known_core) COAP_WELL_KNOWN_CORE_DEFAULT_HANDLER;
+#endif
+
+/* re-define coap_resources for compatibility with non-XFA version */
+#define coap_resources ((const coap_resource_t *)coap_resources_xfa)
+#define coap_resources_numof XFA_LEN(coap_resource_t, coap_resources_xfa)
+#endif
+
 static int _decode_value(unsigned val, uint8_t **pkt_pos_ptr, uint8_t *pkt_end);
 static uint32_t _decode_uint(uint8_t *pkt_pos, unsigned nbytes);
 static size_t _encode_uint(uint32_t *val);