From 690727fe99b944d8346164ccdf59091c29fd173d Mon Sep 17 00:00:00 2001
From: Gunnar Dalsnes <hardon@online.no>
Date: Sun, 9 Oct 2005 22:12:56 +0000
Subject: [PATCH] Fix MulDiv. This fixes almost any progress-bar to stop
 showing negative values during installations or etc. Thanks to kichik for
 originally having found the bug. Patch by alex ionescu

svn path=/trunk/; revision=18386
---
 reactos/lib/kernel32/misc/muldiv.c | 76 ++++++++++++++----------------
 1 file changed, 35 insertions(+), 41 deletions(-)

diff --git a/reactos/lib/kernel32/misc/muldiv.c b/reactos/lib/kernel32/misc/muldiv.c
index 9bb8c895fc8..bbfa3023a49 100644
--- a/reactos/lib/kernel32/misc/muldiv.c
+++ b/reactos/lib/kernel32/misc/muldiv.c
@@ -13,48 +13,42 @@
  *
  * @implemented
  */
-INT STDCALL MulDiv(
-             INT nMultiplicand,
-             INT nMultiplier,
-             INT nDivisor)
+INT
+WINAPI
+MulDiv(INT nNumber,
+       INT nNumerator,
+       INT nDenominator)
 {
-#if SIZEOF_LONG_LONG >= 8
-    long long ret;
-
-    if (!nDivisor) return -1;
-
-    /* We want to deal with a positive divisor to simplify the logic. */
-    if (nDivisor < 0)
+    LARGE_INTEGER Result;
+    LONG Negative;
+ 
+    /* Find out if this will be a negative result */
+    Negative = nNumber ^ nNumerator ^ nDenominator;
+ 
+    /* Turn all the parameters into absolute values */
+    if (nNumber < 0) nNumber *= -1;
+    if (nNumerator < 0) nNumerator *= -1;
+    if (nDenominator < 0) nDenominator *= -1;
+ 
+    /* Calculate the result */
+    Result.QuadPart = Int32x32To64(nNumber, nNumerator) + (nDenominator / 2);
+ 
+    /* Now check for overflow */
+    if (nDenominator > Result.HighPart)
     {
-      nMultiplicand = - nMultiplicand;
-      nDivisor = -nDivisor;
+        /* Divide the product to get the quotient and remainder */
+        Result.LowPart = RtlEnlargedUnsignedDivide(*(PULARGE_INTEGER)&Result,
+                                                   (ULONG)nDenominator,
+                                                   &Result.HighPart);
+ 
+        /* Do the sign changes */
+        if ((LONG)Result.LowPart >= 0)
+        {
+            return (Negative >= 0) ? Result.LowPart : -(LONG)Result.LowPart;
+        }
     }
-
-    /* If the result is positive, we "add" to round. else, we subtract to round. */
-    if ( ( (nMultiplicand <  0) && (nMultiplier <  0) ) ||
-         ( (nMultiplicand >= 0) && (nMultiplier >= 0) ) )
-      ret = (((long long)nMultiplicand * nMultiplier) + (nDivisor/2)) / nDivisor;
-    else
-      ret = (((long long)nMultiplicand * nMultiplier) - (nDivisor/2)) / nDivisor;
-
-    if ((ret > 2147483647) || (ret < -2147483647)) return -1;
-    return ret;
-#else
-    if (!nDivisor) return -1;
-
-    /* We want to deal with a positive divisor to simplify the logic. */
-    if (nDivisor < 0)
-    {
-      nMultiplicand = - nMultiplicand;
-      nDivisor = -nDivisor;
-    }
-
-    /* If the result is positive, we "add" to round. else, we subtract to round. */
-    if ( ( (nMultiplicand <  0) && (nMultiplier <  0) ) ||
-         ( (nMultiplicand >= 0) && (nMultiplier >= 0) ) )
-      return ((nMultiplicand * nMultiplier) + (nDivisor/2)) / nDivisor;
-
-    return ((nMultiplicand * nMultiplier) - (nDivisor/2)) / nDivisor;
-
-#endif
+ 
+    /* Return overflow */
+    return - 1;
 }
+