Merge pull request #13726 from benpicco/nanocoap-payload_helper

nanocoap: add payload helper functions

sys/include/net/nanocoap.h

@@ -78,6 +78,7 @@
 #define NET_NANOCOAP_H
 
 #include <assert.h>
+#include <errno.h>
 #include <stdint.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -1565,6 +1566,63 @@ int coap_parse(coap_pkt_t *pkt, uint8_t *buf, size_t len);
  */
 void coap_pkt_init(coap_pkt_t *pkt, uint8_t *buf, size_t len, size_t header_len);
 
+/**
+ * @brief   Advance the payload pointer.
+ *
+ * @pre     You added @p len bytes of data to `pkt->payload`.
+ *
+ * You can add payload to a CoAP request by writing data directly to
+ * `pkt->payload`.
+ * This convenience function takes care of advancing the payload pointer
+ * afterwards.
+ *
+ * @param[out]   pkt        pkt to which payload was added
+ * @param[in]    len        length of payload
+ */
+static inline void coap_payload_advance_bytes(coap_pkt_t *pkt, size_t len)
+{
+    pkt->payload += len;
+    pkt->payload_len -= len;
+}
+
+/**
+ * @brief   Add payload data to the CoAP request.
+ *
+ * @pre     @ref coap_opt_finish must have been called before with
+ *               the @ref COAP_OPT_FINISH_PAYLOAD option.
+ *
+ * The function copies @p data into the payload buffer of @p pkt and
+ * advances the payload pointer.
+ *
+ * This is just a convenience function, you can also directly write
+ * to `pkt->payload` if you have a function that outputs payload to
+ * a buffer.
+ * In this case you should instead call @ref coap_payload_advance_bytes.
+ *
+ * @param[out]   pkt        pkt to add payload to
+ * @param[in]    data       payload data
+ * @param[in]    len        length of payload
+ *
+ * @returns      number of payload bytes added on success
+ * @returns      < 0 on error
+ */
+ssize_t coap_payload_put_bytes(coap_pkt_t *pkt, const void *data, size_t len);
+
+/**
+ * @brief Add a single character to the payload data of the CoAP request
+ *
+ * This function is used to add single characters to a CoAP payload data. It
+ * checks whether the character can be added to the buffer and ignores if the
+ * payload area is already exhausted.
+ *
+ * @param[out]   pkt        pkt to add payload to
+ * @param[in]    c          character to write
+ *
+ * @returns      number of payload bytes added on success (always one)
+ * @returns      < 0 on error
+ */
+ssize_t coap_payload_put_char(coap_pkt_t *pkt, char c);
+
 /**
  * @brief   Create CoAP reply (convenience function)
  *

sys/net/application_layer/nanocoap/nanocoap.c

@@ -936,6 +936,30 @@ ssize_t coap_opt_finish(coap_pkt_t *pkt, uint16_t flags)
     return pkt->payload - (uint8_t *)pkt->hdr;
 }
 
+ssize_t coap_payload_put_bytes(coap_pkt_t *pkt, const void *data, size_t len)
+{
+    if (pkt->payload_len < len) {
+        return -ENOSPC;
+    }
+
+    memcpy(pkt->payload, data, len);
+    coap_payload_advance_bytes(pkt, len);
+
+    return len;
+}
+
+ssize_t coap_payload_put_char(coap_pkt_t *pkt, char c)
+{
+    if (pkt->payload_len < 1) {
+        return -ENOSPC;
+    }
+
+    *pkt->payload++ = c;
+    pkt->payload_len--;
+
+    return 1;
+}
+
 void coap_block_object_init(coap_block1_t *block, size_t blknum, size_t blksize,
                             int more)
 {