support serde instance

fi/include/frequent_items_sketch.hpp

@@ -225,9 +225,11 @@ class frequent_items_sketch {
   /**
    * Computes size needed to serialize the current state of the sketch.
    * This can be expensive since every item needs to be looked at.
+   * @param instance of a SerDe
    * @return size in bytes needed to serialize this sketch
    */
-  size_t get_serialized_size_bytes() const;
+  template<typename SerDe = S>
+  size_t get_serialized_size_bytes(const SerDe& sd = SerDe()) const;
 
   /**
    * This method serializes the sketch into a given stream in a binary form

fi/include/frequent_items_sketch_impl.hpp

@@ -212,10 +212,11 @@ void frequent_items_sketch<T, W, H, E, S, A>::serialize(std::ostream& os, const
 }
 
 template<typename T, typename W, typename H, typename E, typename S, typename A>
-size_t frequent_items_sketch<T, W, H, E, S, A>::get_serialized_size_bytes() const {
+template<typename SerDe>
+size_t frequent_items_sketch<T, W, H, E, S, A>::get_serialized_size_bytes(const SerDe& sd) const {
   if (is_empty()) return PREAMBLE_LONGS_EMPTY * sizeof(uint64_t);
   size_t size = PREAMBLE_LONGS_NONEMPTY * sizeof(uint64_t) + map.get_num_active() * sizeof(W);
-  for (auto it: map) size += S().size_of_item(it.first);
+  for (auto it: map) size += sd.size_of_item(it.first);
   return size;
 }
 

python/src/fi_wrapper.cpp

@@ -64,6 +64,11 @@ py::list fi_sketch_get_frequent_items(const frequent_items_sketch<T>& sk,
   return list;
 }
 
+template<typename T>
+size_t fi_sketch_get_serialized_size_bytes(const frequent_items_sketch<T>& sk) {
+  return sk.get_serialized_size_bytes();
+}
+
 }
 }
 
@@ -104,7 +109,7 @@ void bind_fi_sketch(py::module &m, const char* name) {
          "Returns the epsilon value used to compute a priori error for a given log2(max_map_size)")
     .def_static("get_apriori_error", &frequent_items_sketch<T>::get_apriori_error, py::arg("lg_max_map_size"), py::arg("estimated_total_weight"),
          "Returns the estimated a priori error given the max_map_size for the sketch and the estimated_total_stream_weight.")
-    .def("get_serialized_size_bytes", &frequent_items_sketch<T>::get_serialized_size_bytes,
+    .def("get_serialized_size_bytes", &dspy::fi_sketch_get_serialized_size_bytes<T>,
          "Computes the size needed to serialize the current state of the sketch. This can be expensive since every item needs to be looked at.")
     .def("serialize", &dspy::fi_sketch_serialize<T>, "Serializes the sketch into a bytes object")
     .def_static("deserialize", &dspy::fi_sketch_deserialize<T>, "Reads a bytes object and returns the corresponding frequent_strings_sketch")