public: optimize COM_FileExtension

public/crtlib.c

@@ -528,22 +528,16 @@ COM_FileExtension
 */
 const char *COM_FileExtension( const char *in )
 {
-	const char *separator, *backslash, *colon, *dot;
-
-	separator = Q_strrchr( in, '/' );
-	backslash = Q_strrchr( in, '\\' );
-
-	if( !separator || separator < backslash )
-		separator = backslash;
-
-	colon = Q_strrchr( in, ':' );
-
-	if( !separator || separator < colon )
-		separator = colon;
+	const char *dot;
 
 	dot = Q_strrchr( in, '.' );
 
-	if( dot == NULL || ( separator && ( dot < separator )))
+	// quickly exit if there is no dot at all
+	if( dot == NULL )
+		return "";
+
+	// if there are any of these special symbols after the dot, the file has no extension
+	if( Q_strpbrk( dot + 1, "\\/:" ))
 		return "";
 
 	return dot + 1;

public/tests/test_fileext.c

@@ -0,0 +1,25 @@
+#include "crtlib.h"
+
+int main( int argc, char **argv )
+{
+	int i;
+	const char *strings[] =
+	{
+		"test.txt", "txt",
+		"path/to/file.wad", "wad",
+		"noext", "",
+		"dir/", "",
+		"dir.pk3dir/", "",
+		"https.proto://is_this_an_url?", "",
+		"inside.wad/AAATRIGGER", "",
+		"c:/games/gamedir/liblist.cum", "cum",
+	};
+
+	for( i = 0; i < sizeof( strings ) / sizeof( strings[0] ); i += 2 )
+	{
+		if( Q_strcmp( COM_FileExtension( strings[i] ), strings[i + 1] ))
+			return i;
+	}
+
+	return 0;
+}

public/wscript

@@ -134,6 +134,7 @@ def build(bld):
 			'strings': 'tests/test_strings.c',
 			'build': 'tests/test_build.c',
 			'filebase': 'tests/test_filebase.c',
+			'fileext': 'tests/test_fileext.c',
 			'efp': 'tests/test_efp.c',
 			'atoi': 'tests/test_atoi.c',
 			'parsefile': 'tests/test_parsefile.c',