libflux/rpc: add aux_get/set, type_get/set

This will assist with wrapping/extending flux_rpc_t for specific RPC classes.

src/common/libflux/rpc.c

@@ -50,6 +50,9 @@ struct flux_rpc_struct {
     flux_msg_t *rx_msg_consumed;
     int rx_count;
     bool oneway;
+    void *aux;
+    flux_free_f aux_destroy;
+    const char *type;
 };
 
 void flux_rpc_destroy (flux_rpc_t *rpc)
@@ -71,6 +74,8 @@ void flux_rpc_destroy (flux_rpc_t *rpc)
         flux_msg_destroy (rpc->rx_msg_consumed);
         if (rpc->nodemap)
             free (rpc->nodemap);
+        if (rpc->aux && rpc->aux_destroy)
+            rpc->aux_destroy (rpc->aux);
         free (rpc);
     }
 }
@@ -295,6 +300,29 @@ flux_rpc_t *flux_rpc_multi (flux_t h, const char *topic, const char *json_str,
     return NULL;
 }
 
+const char *flux_rpc_type_get (flux_rpc_t *rpc)
+{
+    return rpc->type;
+}
+
+void flux_rpc_type_set (flux_rpc_t *rpc, const char *type)
+{
+    rpc->type = type;
+}
+
+void *flux_rpc_aux_get (flux_rpc_t *rpc)
+{
+    return rpc->aux;
+}
+
+void flux_rpc_aux_set (flux_rpc_t *rpc, void *aux, flux_free_f destroy)
+{
+    if (rpc->aux && rpc->aux_destroy)
+        rpc->aux_destroy (rpc->aux);
+    rpc->aux = aux;
+    rpc->aux_destroy = destroy;
+}
+
 /*
  * vi:tabstop=4 shiftwidth=4 expandtab
  */

src/common/libflux/rpc.h

@@ -52,6 +52,13 @@ flux_rpc_t *flux_rpc_multi (flux_t h, const char *topic, const char *json_str,
  */
 bool flux_rpc_completed (flux_rpc_t *rpc);
 
+/* Helper functions for extending flux_rpc_t.
+ */
+const char *flux_rpc_type_get (flux_rpc_t *rpc);
+void flux_rpc_type_set (flux_rpc_t *rpc, const char *type);
+void *flux_rpc_aux_get (flux_rpc_t *rpc);
+void flux_rpc_aux_set (flux_rpc_t *rpc, void *aux, flux_free_f destroy);
+
 #endif /* !_FLUX_CORE_RPC_H */
 
 /*