ulong to string conversion

src/cryptoki.hxx

@@ -62,6 +62,18 @@ namespace cryptoki {
       return data;
   }
 
+  inline std::string string(CK_ULONG num) {
+    switch (num) {
+      case CK_UNAVAILABLE_INFORMATION: return "-";
+      case CK_EFFECTIVELY_INFINITE: return "∞";
+      default: {
+        std::stringstream ss;
+        ss<<num;
+        return ss.str();
+      }
+    }
+  }
+
   template <int NUM, typename TYPE> std::vector<TYPE> toVector(TYPE in[NUM]) {
     return std::vector<TYPE>(in, in+NUM);
   }