From 8ee4bb2586aa08c25568320e4aa2dcd7370f9554 Mon Sep 17 00:00:00 2001
From: Olaf Bergmann <bergmann@tzi.org>
Date: Thu, 16 Nov 2017 14:18:20 +0100
Subject: [PATCH] pdu.c: fix len returned by coap_get_data() for empty payload

John Carter has provided this (slightly edited) patch to set len to 0
for PDUs that do not contain a payload. This makes this function more
robust for callers that do not care about the function result.

This change fixes issue 120 [1].

[1] https://github.com/obgm/libcoap/issues/120
---
 src/pdu.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/pdu.c b/src/pdu.c
index 0e47bbfb..e91e0f93 100644
--- a/src/pdu.c
+++ b/src/pdu.c
@@ -324,9 +324,15 @@ coap_get_data(coap_pdu_t *pdu, size_t *len, uint8_t **data) {
   assert(len);
   assert(data);
 
-  *len = pdu->used_size - (pdu->data - pdu->token);
   *data = pdu->data;
-  return *data != NULL;
+  if(pdu->data == NULL) {
+     *len = 0;
+     return 0;
+  }
+
+  *len = pdu->used_size - (pdu->data - pdu->token);
+
+  return 1;
 }
 
 #ifndef SHORT_ERROR_RESPONSE