stasis: Reduce calculation of stasis message type hash.

When the stasis cache is used a hash is calculated for
retrieving or inserting messages. This change calculates
a hash when the message type is initialized that is then
used each time needed. This ensures that the hash is
calculated only once for the message type.

Change-Id: I4fe6bfdafb55bf5c322dd313fbd8c32cce73ef37

include/asterisk/stasis.h

@@ -318,6 +318,14 @@ enum stasis_message_type_result stasis_message_type_create(const char *name,
  */
 const char *stasis_message_type_name(const struct stasis_message_type *type);
 
+/*!
+ * \brief Gets the hash of a given message type
+ * \param type The type to get the hash of.
+ * \return The hash
+ * \since 13.24.0
+ */
+unsigned int stasis_message_type_hash(const struct stasis_message_type *type);
+
 /*!
  * \brief Check whether a message type is declined
  *

main/stasis_cache.c

@@ -174,7 +174,7 @@ static void cache_entry_dtor(void *obj)
 
 static void cache_entry_compute_hash(struct cache_entry_key *key)
 {
-	key->hash = ast_hashtab_hash_string(stasis_message_type_name(key->type));
+	key->hash = stasis_message_type_hash(key->type);
 	key->hash += ast_hashtab_hash_string(key->id);
 }
 

main/stasis_message.c

@@ -32,11 +32,13 @@
 #include "asterisk/astobj2.h"
 #include "asterisk/stasis.h"
 #include "asterisk/utils.h"
+#include "asterisk/hashtab.h"
 
 /*! \internal */
 struct stasis_message_type {
 	struct stasis_message_vtable *vtable;
 	char *name;
+	unsigned int hash;
 };
 
 static struct stasis_message_vtable null_vtable = {};
@@ -73,6 +75,7 @@ int stasis_message_type_create(const char *name,
 		ao2_cleanup(type);
 		return STASIS_MESSAGE_TYPE_ERROR;
 	}
+	type->hash = ast_hashtab_hash_string(name);
 	type->vtable = vtable;
 	*result = type;
 
@@ -84,6 +87,11 @@ const char *stasis_message_type_name(const struct stasis_message_type *type)
 	return type->name;
 }
 
+unsigned int stasis_message_type_hash(const struct stasis_message_type *type)
+{
+	return type->hash;
+}
+
 /*! \internal */
 struct stasis_message {
 	/*! Time the message was created */