setupapi: Fix hex digit check in SetupGetBinaryField.

dlls/setupapi/parser.c

@@ -1803,6 +1803,15 @@ BOOL WINAPI SetupGetIntField( PINFCONTEXT context, DWORD index, PINT result )
 }
 
 
+static int xdigit_to_int(WCHAR c)
+{
+    if ('0' <= c && c <= '9') return c - '0';
+    if ('a' <= c && c <= 'f') return c - 'a' + 10;
+    if ('A' <= c && c <= 'F') return c - 'A' + 10;
+    return -1;
+}
+
+
 /***********************************************************************
  *		SetupGetBinaryField    (SETUPAPI.@)
  */
@@ -1837,15 +1846,15 @@ BOOL WINAPI SetupGetBinaryField( PINFCONTEXT context, DWORD index, BYTE *buffer,
     {
         const WCHAR *p;
         DWORD value = 0;
-        for (p = field->text; *p && iswxdigit(*p); p++)
+        int d;
+        for (p = field->text; *p && (d = xdigit_to_int(*p)) != -1; p++)
         {
             if ((value <<= 4) > 255)
             {
                 SetLastError( ERROR_INVALID_DATA );
                 return FALSE;
             }
-            if (*p <= '9') value |= (*p - '0');
-            else value |= (towlower(*p) - 'a' + 10);
+            value |= d;
         }
         buffer[i - index] = value;
     }