Add a new EVUTIL_UPCAST macro so that I do not need to keep figuring …

…out the right offsetof magic over and over. svn:r1160
thinkinnight · Apr 12, 2009 · 0b47b12 · 0b47b12
1 parent bbd6a33
commit 0b47b12
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Showing 2 changed files with 5 additions and 2 deletions.
diff --git a/bufferevent_pair.c b/bufferevent_pair.c
@@ -39,6 +39,7 @@
 #include "defer-internal.h"
 #include "bufferevent-internal.h"
 #include "mm-internal.h"
+#include "util-internal.h"
 
 struct bufferevent_pair {
 	struct bufferevent bev;
@@ -56,8 +57,7 @@ upcast(struct bufferevent *bev)
 	struct bufferevent_pair *bev_p;
 	if (bev->be_ops != &bufferevent_ops_pair)
 		return NULL;
-	bev_p = (void*)( ((char*)bev) -
-			 evutil_offsetof(struct bufferevent_pair, bev) );
+	bev_p = EVUTIL_UPCAST(bev, struct bufferevent_pair, bev);
 	assert(bev_p->bev.be_ops == &bufferevent_ops_pair);
 	return bev_p;
 }

diff --git a/util-internal.h b/util-internal.h
@@ -101,6 +101,9 @@ extern const char EVUTIL_TOLOWER_TABLE[];
 #define EVUTIL_TOLOWER(c) (EVUTIL_TOLOWER_TABLE[(ev_uint8_t)c])
 #define EVUTIL_TOUPPER(c) (EVUTIL_TOUPPER_TABLE[(ev_uint8_t)c])
 
+#define EVUTIL_UPCAST(ptr, type, field)				\
+	((type *)((char*)ptr) - evutil_offsetof(type, field))
+
 #ifdef __cplusplus
 }
 #endif