sat-math: Introduce macro version of SAT_MUL.

The macro version can be used in a constant expression, such as an
initializer for a variable with static lifetime.  (Otherwise, it's better
to use the function.)

Signed-off-by: Ben Pfaff <blp@nicira.com>

diff --git a/lib/sat-math.h b/lib/sat-math.h
index ae504ba143b8e6fc1e1c763e81d937019617dd34..f4287fc250685d0320d8fbced9a1e716657dafcd 100644 (file)
--- a/lib/sat-math.h
+++ b/lib/sat-math.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008 Nicira, Inc.
+ * Copyright (c) 2008, 2012 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,13 +34,15 @@ sat_sub(unsigned int x, unsigned int y)
     return x >= y ? x - y : 0;
 }
 
-/* Saturating multiplication: overflow yields UINT_MAX. */
+/* Saturating multiplication of "unsigned int"s: overflow yields UINT_MAX. */
+#define SAT_MUL(X, Y)                                                   \
+    ((Y) == 0 ? 0                                                       \
+     : (X) <= UINT_MAX / (Y) ? (unsigned int) (X) * (unsigned int) (Y)  \
+     : UINT_MAX)
 static inline unsigned int
 sat_mul(unsigned int x, unsigned int y)
 {
-    return (!y ? 0
-            : x <= UINT_MAX / y ? x * y
-            : UINT_MAX);
+    return SAT_MUL(x, y);
 }
 
 #endif /* sat-math.h */