Add void* arguments to request_new and reply_new evrpc hooks

This makes evprc setup more extensible, and helps with Shuo Chen's
work on implementing Google protocol buffers rpc on top of Libevent 2
evrpc.

This patch breaks binary compatibility with previous versions of
Libevent, since it changes struct evrpc and the signature of
evrpc_register_generic().  Since all compliant code should be calling
evrpc_register_generic via EVRPC_REGISTER, it shouldn't break source
compatibility.

(Code by Shuo Chen; commit message by Nick)

event_rpcgen.py

@@ -117,6 +117,7 @@ class StructCCode(Struct):
 
         print >>file, \
 """struct %(name)s *%(name)s_new(void);
+struct %(name)s *%(name)s_new_with_arg(void *);
 void %(name)s_free(struct %(name)s *);
 void %(name)s_clear(struct %(name)s *);
 void %(name)s_marshal(struct evbuffer *, const struct %(name)s *);
@@ -157,6 +158,12 @@ int evtag_unmarshal_%(name)s(struct evbuffer *, ev_uint32_t,
             'struct %(name)s *\n'
             '%(name)s_new(void)\n'
             '{\n'
+            '  return %(name)s_new_with_arg(NULL);\n'
+            '}\n'
+            '\n'
+            'struct %(name)s *\n'
+            '%(name)s_new_with_arg(void *unused)\n'
+            '{\n'
             '  struct %(name)s *tmp;\n'
             '  if ((tmp = malloc(sizeof(struct %(name)s))) == NULL) {\n'
             '    event_warn("%%s: malloc", __func__);\n'

evrpc.c

@@ -339,7 +339,7 @@ evrpc_request_cb_closure(void *arg, enum EVRPC_HOOK_RESULT hook_res)
 		goto error;
 
 	/* let's check that we can parse the request */
-	rpc_state->request = rpc->request_new();
+	rpc_state->request = rpc->request_new(rpc->request_new_arg);
 	if (rpc_state->request == NULL)
 		goto error;
 
@@ -351,7 +351,7 @@ evrpc_request_cb_closure(void *arg, enum EVRPC_HOOK_RESULT hook_res)
 
 	/* at this point, we have a well formed request, prepare the reply */
 
-	rpc_state->reply = rpc->reply_new();
+	rpc_state->reply = rpc->reply_new(rpc->reply_new_arg);
 	if (rpc_state->reply == NULL)
 		goto error;
 
@@ -1081,9 +1081,9 @@ error:
 /** Takes a request object and fills it in with the right magic */
 static struct evrpc *
 evrpc_register_object(const char *name,
-    void *(*req_new)(void), void (*req_free)(void *),
+    void *(*req_new)(void*), void *req_new_arg, void (*req_free)(void *),
     int (*req_unmarshal)(void *, struct evbuffer *),
-    void *(*rpl_new)(void), void (*rpl_free)(void *),
+    void *(*rpl_new)(void*), void *rpl_new_arg, void (*rpl_free)(void *),
     int (*rpl_complete)(void *),
     void (*rpl_marshal)(struct evbuffer *, void *))
 {
@@ -1096,9 +1096,11 @@ evrpc_register_object(const char *name,
 		return (NULL);
 	}
 	rpc->request_new = req_new;
+	rpc->request_new_arg = req_new_arg;
 	rpc->request_free = req_free;
 	rpc->request_unmarshal = req_unmarshal;
 	rpc->reply_new = rpl_new;
+	rpc->reply_new_arg = rpl_new_arg;
 	rpc->reply_free = rpl_free;
 	rpc->reply_complete = rpl_complete;
 	rpc->reply_marshal = rpl_marshal;
@@ -1108,15 +1110,15 @@ evrpc_register_object(const char *name,
 int
 evrpc_register_generic(struct evrpc_base *base, const char *name,
     void (*callback)(struct evrpc_req_generic *, void *), void *cbarg,
-    void *(*req_new)(void), void (*req_free)(void *),
+    void *(*req_new)(void *), void *req_new_arg, void (*req_free)(void *),
     int (*req_unmarshal)(void *, struct evbuffer *),
-    void *(*rpl_new)(void), void (*rpl_free)(void *),
+    void *(*rpl_new)(void *), void *rpl_new_arg, void (*rpl_free)(void *),
     int (*rpl_complete)(void *),
     void (*rpl_marshal)(struct evbuffer *, void *))
 {
 	struct evrpc* rpc =
-	    evrpc_register_object(name, req_new, req_free, req_unmarshal,
+	    evrpc_register_object(name, req_new, req_new_arg, req_free, req_unmarshal,
-		rpl_new, rpl_free, rpl_complete, rpl_marshal);
+		rpl_new, rpl_new_arg, rpl_free, rpl_complete, rpl_marshal);
 	if (rpc == NULL)
 		return (-1);
 	evrpc_register_rpc(base, rpc,

include/event2/rpc.h

@@ -319,10 +319,10 @@ void evrpc_free(struct evrpc_base *base);
 #define EVRPC_REGISTER(base, name, request, reply, callback, cbarg)	\
 	evrpc_register_generic(base, #name,				\
 	    (void (*)(struct evrpc_req_generic *, void *))callback, cbarg, \
-	    (void *(*)(void))request##_new,				\
+	    (void *(*)(void *))request##_new, NULL,			\
 	    (void (*)(void *))request##_free,				\
 	    (int (*)(void *, struct evbuffer *))request##_unmarshal,	\
-	    (void *(*)(void))reply##_new, \
+	    (void *(*)(void *))reply##_new, NULL,			\
 	    (void (*)(void *))reply##_free, \
 	    (int (*)(void *))reply##_complete, \
 	    (void (*)(struct evbuffer *, void *))reply##_marshal)
@@ -575,9 +575,9 @@ int evrpc_send_request_generic(struct evrpc_pool *pool,
 int
 evrpc_register_generic(struct evrpc_base *base, const char *name,
     void (*callback)(struct evrpc_req_generic *, void *), void *cbarg,
-    void *(*req_new)(void), void (*req_free)(void *),
+    void *(*req_new)(void *), void *req_new_arg, void (*req_free)(void *),
     int (*req_unmarshal)(void *, struct evbuffer *),
-    void *(*rpl_new)(void), void (*rpl_free)(void *),
+    void *(*rpl_new)(void *), void *rpl_new_arg, void (*rpl_free)(void *),
     int (*rpl_complete)(void *),
     void (*rpl_marshal)(struct evbuffer *, void *));
 

include/event2/rpc_struct.h

@@ -63,7 +63,8 @@ struct evrpc {
 	const char* uri;
 
 	/* creates a new request structure */
-	void *(*request_new)(void);
+	void *(*request_new)(void *);
+	void *request_new_arg;
 
 	/* frees the request structure */
 	void (*request_free)(void *);
@@ -72,9 +73,10 @@ struct evrpc {
 	int (*request_unmarshal)(void *, struct evbuffer *);
 
 	/* creates a new reply structure */
-	void *(*reply_new)(void);
+	void *(*reply_new)(void *);
+	void *reply_new_arg;
 
-	/* creates a new reply structure */
+	/* frees the reply structure */
 	void (*reply_free)(void *);
 
 	/* verifies that the reply is valid */