X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Fstructeq%2Fstructeq.h;h=81799539c51e45f9c2f1b9c23a1b3949b47564c1;hp=3af20c53938ce73276da8afa7dfa441d9f3766ed;hb=8e6c2fecfd633171250b7f09ef4aa0328bd5b698;hpb=8b0bdb090e2882aa431e89f4bc7aa4736e9e2838

diff --git a/ccan/structeq/structeq.h b/ccan/structeq/structeq.h
index 3af20c53..81799539 100644
--- a/ccan/structeq/structeq.h
+++ b/ccan/structeq/structeq.h
@@ -1,17 +1,46 @@
-/* CC0 (Public domain) - see LICENSE file for details */
+/* MIT (BSD) license - see LICENSE file for details */
 #ifndef CCAN_STRUCTEQ_H
 #define CCAN_STRUCTEQ_H
+#include <ccan/build_assert/build_assert.h>
+#include <ccan/cppmagic/cppmagic.h>
 #include <string.h>
+#include <stdbool.h>
 
 /**
- * structeq - are two structures bitwise equal (including padding!)
- * @a: a pointer to a structure
- * @b: a pointer to a structure of the same type.
+ * STRUCTEQ_DEF - define an ..._eq function to compare two structures.
+ * @sname: name of the structure, and function (<sname>_eq) to define.
+ * @padbytes: number of bytes of expected padding, or negative "max".
+ * @...: name of every member of the structure.
  *
- * If you *know* a structure has no padding, you can memcmp them.  At
- * least this way, the compiler will issue a warning if the structs are
- * different types!
+ * This generates a single memcmp() call in the common case where the
+ * structure contains no padding.  Since it can't tell the difference between
+ * padding and a missing member, @padbytes can be used to assert that
+ * there isn't any, or how many we expect.  A negative number means
+ * "up to or equal to that amount of padding", as padding can be
+ * platform dependent.
  */
-#define structeq(a, b) \
-	(memcmp((a), (b), sizeof(*(a)) + 0 * sizeof((a) == (b))) == 0)
+#define STRUCTEQ_DEF(sname, padbytes, ...)				\
+static inline bool CPPMAGIC_GLUE2(sname, _eq)(const struct sname *_a, \
+					      const struct sname *_b) \
+{									\
+	BUILD_ASSERT(((padbytes) < 0 &&					\
+		      CPPMAGIC_JOIN(+, CPPMAGIC_MAP(STRUCTEQ_MEMBER_SIZE_, \
+						    __VA_ARGS__))	\
+		      - (padbytes) >= sizeof(*_a))			\
+		     || CPPMAGIC_JOIN(+, CPPMAGIC_MAP(STRUCTEQ_MEMBER_SIZE_, \
+						      __VA_ARGS__))	\
+		     + (padbytes) == sizeof(*_a));			\
+	if (CPPMAGIC_JOIN(+, CPPMAGIC_MAP(STRUCTEQ_MEMBER_SIZE_, __VA_ARGS__)) \
+	    == sizeof(*_a))						\
+		return memcmp(_a, _b, sizeof(*_a)) == 0;		\
+	else								\
+		return CPPMAGIC_JOIN(&&,				\
+				     CPPMAGIC_MAP(STRUCTEQ_MEMBER_CMP_, \
+						  __VA_ARGS__));	\
+}
+
+/* Helpers */
+#define STRUCTEQ_MEMBER_SIZE_(m) sizeof((_a)->m)
+#define STRUCTEQ_MEMBER_CMP_(m) memcmp(&_a->m, &_b->m, sizeof(_a->m)) == 0
+
 #endif /* CCAN_STRUCTEQ_H */