zoap: Add support for retrieving the underlying net_buf

Add an alternative to zoap_packet_get_payload(), that instead of
returning a byte array, returns the net_buf (with the COAP_MARKER
added, if needed) associated with the packet, positioned so the
application can add more data.

Change-Id: I7c955ef42f5ef8406d77da994d1673e6a69b0b6b
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>

2 files changed, 20 insertions, 0 deletions

diff --git a/lib/iot/zoap/zoap.c b/lib/iot/zoap/zoap.c
index 430d50e0a..fd479236e 100644
--- a/lib/iot/zoap/zoap.c
+++ b/lib/iot/zoap/zoap.c
@@ -795,6 +795,20 @@ int zoap_packet_set_used(struct zoap_packet *pkt, uint16_t len)
 	return 0;
 }
 
+struct net_buf *zoap_packet_get_buf(struct zoap_packet *pkt)
+{
+	struct net_buf *frag = pkt->buf->frags;
+	uint8_t *str;
+
+	if (!pkt->start) {
+		str = net_buf_add(frag, 1);
+		*str = COAP_MARKER;
+		pkt->start = str + 1;
+	}
+
+	return frag;
+}
+
 int zoap_add_option(struct zoap_packet *pkt, uint16_t code,
 		    const void *value, uint16_t len)
 {
diff --git a/lib/iot/zoap/zoap.h b/lib/iot/zoap/zoap.h
index 451c61428..2d5251136 100644
--- a/lib/iot/zoap/zoap.h
+++ b/lib/iot/zoap/zoap.h
@@ -371,6 +371,12 @@ bool zoap_request_is_observe(const struct zoap_packet *request);
 uint8_t *zoap_packet_get_payload(struct zoap_packet *pkt, uint16_t *len);
 
 /**
+ * Returns the internal buffer of the CoAP packet, appending the
+ * COAP_MARKER to the buffer if necessary.
+ */
+struct net_buf *zoap_packet_get_buf(struct zoap_packet *pkt);
+
+/**
  * Sets how much space was used by the payload.
  */
 int zoap_packet_set_used(struct zoap_packet *pkt, uint16_t len);