improve pb reader

iguana/pb_reader.hpp

@@ -73,20 +73,23 @@ IGUANA_INLINE void from_pb_impl(T& val, std::string_view& pb_str,
               "Invalid fixed int value: too few bytes.");
         }
       if constexpr (is_fixed_v<item_type>) {
-        int num = size / sizeof(item_type);
-        int old_size = val.size();
+        size_t num = size / sizeof(item_type);
+        size_t old_size = val.size();
         detail::resize(val, old_size + num);
         std::memcpy(val.data() + old_size, pb_str.data(), size);
         pb_str = pb_str.substr(size);
       }
       else {
+        detail::resize(val, size);
+        size_t index = 0;
         size_t start = pb_str.size();
-
-        while (!pb_str.empty()) {
-          item_type item;
-          from_pb_impl(item, pb_str);
-          val.push_back(std::move(item));
+        while (!pb_str.empty() && index < size) {
+          from_pb_impl(val[index], pb_str);
+          index++;
           if (start - pb_str.size() == size) {
+            if (index < size) {
+              detail::resize(val, index);
+            }
             break;
           }
         }