Implemented get_percentage() for compact and safe calculation of percentual values.

Fixed integer arithmetic overflows that were occuring in several supernovice checks (bugreport:1135).

git-svn-id: https://rathena.svn.sourceforge.net/svnroot/rathena/trunk@12679 54d463be-8e91-2dee-dedb-b68131a5f0ec

2 files changed, 19 insertions, 0 deletions

diff --git a/src/common/utils.c b/src/common/utils.c
index 354bd3814..a9ce1389f 100644
--- a/src/common/utils.c
+++ b/src/common/utils.c
@@ -221,3 +221,19 @@ uint32 MakeDWord(uint16 word0, uint16 word1)
 		( (uint32)(word0        ) )|
 		( (uint32)(word1 << 0x10) );
 }
+
+
+/// calculates the value of A / B, in percent (rounded down)
+unsigned int percent(const unsigned int A, const unsigned int B)
+{
+	if( B == 0 )
+	{
+		ShowError("percent(): divison by zero!\n");
+		return -1;
+	}
+
+	if( A < UINT_MAX/100 )
+		return 100*A/B;
+	else
+		return A/(B/100);
+}
\ No newline at end of file
diff --git a/src/common/utils.h b/src/common/utils.h
index 21e8e090c..93563dc34 100644
--- a/src/common/utils.h
+++ b/src/common/utils.h
@@ -18,6 +18,9 @@ void findfile(const char *p, const char *pat, void (func)(const char*));
 //Caps values to min/max
 #define cap_value(a, min, max) ((a >= max) ? max : (a <= min) ? min : a)
 
+/// calculates the value of A / B, in percent (rounded down)
+unsigned int get_percentage(const unsigned int A, const unsigned int B);
+
 //////////////////////////////////////////////////////////////////////////
 // byte word dword access [Shinomori]
 //////////////////////////////////////////////////////////////////////////