Update for changes on Cyclone DDS security branch

The security specification has a mode in which keyhashes containing the
MD5 of the key value are required on the wire, and this requires some
small changes to the topic interface.  Currently, these changes reside
only on the security branch of Cyclone DDS.

The changes use conditional compilation to handle both the master branch
of Cyclone and the security branch to minimise version dependencies.

Signed-off-by: Erik Boasson <eb@ilities.com>

rmw_cyclonedds_cpp/src/serdata.cpp

@@ -31,6 +31,18 @@
 #include "rmw_cyclonedds_cpp/ServiceTypeSupport.hpp"
 #include "rmw_cyclonedds_cpp/serdes.hpp"
 
+/* Cyclone's nn_keyhash got renamed to ddsi_keyhash and shuffled around in the header
+   files to avoid pulling in tons of things just for a definition of a keyhash.  This
+   coincides with the introduction of DDS Security, which itself adds another function
+   that was missing.
+
+   If that additional function is not needed, it is known as nn_keyhash and only a forward
+   declaration is available; else it is known as ddsi_keyhash and a definition is
+   available */
+#if !DDSI_SERDATA_HAS_GET_KEYHASH
+#define ddsi_keyhash nn_keyhash
+#endif
+
 using MessageTypeSupport_c =
   rmw_cyclonedds_cpp::MessageTypeSupport<rosidl_typesupport_introspection_c__MessageMembers>;
 using MessageTypeSupport_cpp =
@@ -173,7 +185,7 @@ static struct ddsi_serdata * serdata_rmw_from_ser_iov(
 
 static struct ddsi_serdata * serdata_rmw_from_keyhash(
   const struct ddsi_sertopic * topic,
-  const struct nn_keyhash * keyhash)
+  const struct ddsi_keyhash * keyhash)
 {
   static_cast<void>(keyhash);    // unused
   /* there is no key field, so from_keyhash is trivial */
@@ -377,6 +389,19 @@ static size_t serdata_rmw_print(
 }
 #endif
 
+#if DDSI_SERDATA_HAS_GET_KEYHASH
+static void serdata_rmw_get_keyhash(
+  const struct ddsi_serdata * d, struct ddsi_keyhash * buf,
+  bool force_md5)
+{
+  /* ROS2 doesn't do keys in a meaningful way yet, this is never called for topics without
+     key fields */
+  static_cast<void>(d);
+  static_cast<void>(force_md5);
+  memset(buf, 0, sizeof(*buf));
+}
+#endif
+
 static const struct ddsi_serdata_ops serdata_rmw_ops = {
   serdata_rmw_eqkey,
   serdata_rmw_size,
@@ -396,6 +421,9 @@ static const struct ddsi_serdata_ops serdata_rmw_ops = {
 #if DDSI_SERDATA_HAS_PRINT
   , serdata_rmw_print
 #endif
+#if DDSI_SERDATA_HAS_GET_KEYHASH
+  , serdata_rmw_get_keyhash
+#endif
 };
 
 static void sertopic_rmw_free(struct ddsi_sertopic * tpcmn)