net/nanocoap: add function to retrieve opaque option

sys/include/net/nanocoap.h

@@ -573,6 +573,23 @@ static inline ssize_t coap_get_uri_query(const coap_pkt_t *pkt, uint8_t *target)
  */
 ssize_t coap_opt_get_next(const coap_pkt_t *pkt, coap_optpos_t *opt,
                           uint8_t **value, bool init_opt);
+
+/**
+ * @brief   Retrieve the value for an option as an opaque array of bytes
+ *
+ * Retrieves the location and length of the option value of any type. Useful for
+ * an opaque option, which essentially is an array of bytes. If more than one
+ * option for a given option number, retrieves the first option. To retrieve
+ * subsequent options, see coap_opt_get_next().
+ *
+ * @param[in]     pkt         packet to read from
+ * @param[in]     opt_num     option number to retrieve
+ * @param[out]    value       start of the option value
+ *
+ * @return        length of option; 0 if the option exists but is empty
+ * @return        -ENOENT if option not found
+ */
+ssize_t coap_opt_get_opaque(coap_pkt_t *pkt, unsigned opt_num, uint8_t **value);
 /**@}*/
 
 

sys/net/application_layer/nanocoap/nanocoap.c

@@ -205,6 +205,20 @@ static uint8_t *_parse_option(const coap_pkt_t *pkt,
     return pkt_pos;
 }
 
+ssize_t coap_opt_get_opaque(coap_pkt_t *pkt, unsigned opt_num, uint8_t **value)
+{
+    uint8_t *start = coap_find_option(pkt, opt_num);
+    if (!start) {
+        return -ENOENT;
+    }
+
+    uint16_t delta;
+    int len;
+
+    *value = _parse_option(pkt, start, &delta, &len);
+    return len;
+}
+
 int coap_get_option_uint(coap_pkt_t *pkt, unsigned opt_num, uint32_t *target)
 {
     assert(target);