Improve static and const correctness.

- Any non-externally-visible declarations should be `static`.
- Casting away the `const` qualifier from pointers-to-const is
  dangerous. All but one instance of this are now correct. The one
  instance where we can't keep `const` is one where toxav code actually
  writes to a chunk of memory marked as `const`. This code also assumes
  4 byte alignment of data packets. I don't know whether that is a valid
  assumption, but it's likely unportable, and *not* obviously correct.
- Replaced empty parameter lists with `(void)` to avoid passing
  parameters to it. Empty parameter lists are old style declarations for
  unknown number and type of arguments.
- Commented out (as `#if DHT_HARDENING` block) the hardening code that
  was never executed.
- Minor style fix: don't use `default` in enum-switches unless the number
  of enumerators in the default case is very large. In this case, it was
  2, so we want to list them both explicitly to be warned about missing
  one if we add one in the future.
- Removed the only two function declarations from nTox.h and put them
  into nTox.c. They are not used outside and nTox is not a library.

1 files changed, 12 insertions, 4 deletions

diff --git a/toxcore/DHT.c b/toxcore/DHT.c
index ac94a36e..2e475d01 100644
--- a/toxcore/DHT.c
+++ b/toxcore/DHT.c
@@ -2136,6 +2136,7 @@ static void do_NAT(DHT *dht)
 #define CHECK_TYPE_TEST_REQ 4
 #define CHECK_TYPE_TEST_RES 5
 
+#if DHT_HARDENING
 static int send_hardening_req(DHT *dht, Node_format *sendto, uint8_t type, uint8_t *contents, uint16_t length)
 {
     if (length > HARDREQ_DATA_SIZE - 1) {
@@ -2164,6 +2165,7 @@ static int send_hardening_getnode_req(DHT *dht, Node_format *dest, Node_format *
     memcpy(data + sizeof(Node_format), search_id, crypto_box_PUBLICKEYBYTES);
     return send_hardening_req(dht, dest, CHECK_TYPE_GETNODE_REQ, data, sizeof(Node_format) + crypto_box_PUBLICKEYBYTES);
 }
+#endif
 
 /* Send a get node hardening response */
 static int send_hardening_getnode_res(const DHT *dht, const Node_format *sendto, const uint8_t *queried_client_id,
@@ -2316,10 +2318,11 @@ static int handle_hardening(void *object, IP_Port source, const uint8_t *source_
     return 1;
 }
 
+#if DHT_HARDENING
 /* Return a random node from all the nodes we are connected to.
  * TODO: improve this function.
  */
-Node_format random_node(DHT *dht, sa_family_t sa_family)
+static Node_format random_node(DHT *dht, sa_family_t sa_family)
 {
     uint8_t id[crypto_box_PUBLICKEYBYTES];
     uint32_t i;
@@ -2339,12 +2342,13 @@ Node_format random_node(DHT *dht, sa_family_t sa_family)
 
     return nodes_list[rand() % num_nodes];
 }
+#endif
 
 /* Put up to max_num nodes in nodes from the closelist.
  *
  * return the number of nodes.
  */
-uint16_t list_nodes(Client_data *list, unsigned int length, Node_format *nodes, uint16_t max_num)
+static uint16_t list_nodes(Client_data *list, unsigned int length, Node_format *nodes, uint16_t max_num)
 {
     if (max_num == 0) {
         return 0;
@@ -2417,7 +2421,8 @@ uint16_t closelist_nodes(DHT *dht, Node_format *nodes, uint16_t max_num)
     return list_nodes(dht->close_clientlist, LCLIENT_LIST, nodes, max_num);
 }
 
-void do_hardening(DHT *dht)
+#if DHT_HARDENING
+static void do_hardening(DHT *dht)
 {
     uint32_t i;
 
@@ -2469,6 +2474,7 @@ void do_hardening(DHT *dht)
         //TODO: add the 2 other testers.
     }
 }
+#endif
 
 /*----------------------------------------------------------------------------------*/
 
@@ -2589,7 +2595,9 @@ void do_DHT(DHT *dht)
     do_DHT_friends(dht);
     do_NAT(dht);
     do_to_ping(dht->ping);
-    //do_hardening(dht);
+#if DHT_HARDENING
+    do_hardening(dht);
+#endif
 #ifdef ENABLE_ASSOC_DHT
 
     if (dht->assoc)