lib/simbricks/base: add SimbricksBaseIfSHMSize()

Determines how much shm a particular connection will need based on the
parameters..

lib/simbricks/base/if.c

@@ -153,6 +153,12 @@ void SimbricksBaseIfDefaultParams(struct SimbricksBaseIfParams *params)
   params->upper_layer_proto = SIMBRICKS_PROTO_ID_BASE;
 }
 
+size_t SimbricksBaseIfSHMSize(struct SimbricksBaseIfParams *params)
+{
+  return params->in_num_entries * params->in_entries_size +
+      params->out_num_entries * params->out_entries_size;
+}
+
 int SimbricksBaseIfInit(struct SimbricksBaseIf *base_if,
                         struct SimbricksBaseIfParams *params)
 {

lib/simbricks/base/if.h

@@ -124,6 +124,9 @@ int SimbricksBaseIfSHMPoolUnlink(struct SimbricksBaseIfSHMPool *pool);
 /** Initialize params struct with default values */
 void SimbricksBaseIfDefaultParams(struct SimbricksBaseIfParams *params);
 
+/** Required SHM size for these parameters */
+size_t SimbricksBaseIfSHMSize(struct SimbricksBaseIfParams *params);
+
 int SimbricksBaseIfInit(struct SimbricksBaseIf *base_if,
                         struct SimbricksBaseIfParams *params);