From af7051178de9f4b3eccbf9a4c0bd347e12a1f9dd Mon Sep 17 00:00:00 2001
From: frosch <frosch@openttd.org>
Date: Sun, 18 Apr 2010 17:13:01 +0000
Subject: (svn r19671) -Fix (r19670): RoundDiv() needs to deal with signed
 numerators.

---
 src/core/math_func.hpp | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

(limited to 'src/core/math_func.hpp')

diff --git a/src/core/math_func.hpp b/src/core/math_func.hpp
index 8f31dd273..19f2f53d6 100644
--- a/src/core/math_func.hpp
+++ b/src/core/math_func.hpp
@@ -330,14 +330,20 @@ static FORCEINLINE uint CeilDiv(uint a, uint b)
 }
 
 /**
- * Computes round(a / b) for non-negative a and b.
+ * Computes round(a / b) for signed a and unsigned b.
  * @param a Numerator
  * @param b Denominator
  * @return Quotient, rounded to nearest
  */
-static FORCEINLINE uint RoundDiv(uint a, uint b)
+static FORCEINLINE int RoundDivSU(int a, uint b)
 {
-	return (a + b / 2) / b;
+	if (a > 0) {
+		/* 0.5 is rounded to 1 */
+		return (a + (int)b / 2) / (int)b;
+	} else {
+		/* -0.5 is rounded to 0 */
+		return (a - ((int)b - 1) / 2) / (int)b;
+	}
 }
 
 #endif /* MATH_FUNC_HPP */
-- 
cgit v1.2.3-54-g00ecf