From d93427fb52e4418e91f665f88db8869811d0d3e1 Mon Sep 17 00:00:00 2001
From: BlackMATov <blackmatov@gmail.com>
Date: Fri, 12 Apr 2019 20:10:12 +0700
Subject: [PATCH] memory usage stats

---
 ecs.hpp       | 45 +++++++++++++++++++++++++++++++
 ecs_tests.cpp | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 118 insertions(+)

diff --git a/ecs.hpp b/ecs.hpp
index 6224264..9d10a25 100644
--- a/ecs.hpp
+++ b/ecs.hpp
@@ -426,6 +426,11 @@ namespace ecs_hpp
             std::size_t size() const noexcept {
                 return dense_.size();
             }
+
+            std::size_t memory_usage() const noexcept {
+                return dense_.capacity() * sizeof(dense_[0])
+                    + sparse_.capacity() * sizeof(sparse_[0]);
+            }
         private:
             Indexer indexer_;
             std::vector<T> dense_;
@@ -595,6 +600,11 @@ namespace ecs_hpp
             std::size_t size() const noexcept {
                 return values_.size();
             }
+
+            std::size_t memory_usage() const noexcept {
+                return keys_.memory_usage()
+                    + values_.capacity() * sizeof(values_[0]);
+            }
         private:
             sparse_set<K, Indexer> keys_;
             std::vector<T> values_;
@@ -646,6 +656,7 @@ namespace ecs_hpp
             virtual bool remove(entity_id id) noexcept = 0;
             virtual bool has(entity_id id) const noexcept = 0;
             virtual void clone(entity_id from, entity_id to) = 0;
+            virtual std::size_t memory_usage() const noexcept = 0;
         };
 
         template < typename T >
@@ -669,6 +680,8 @@ namespace ecs_hpp
             void for_each_component(F&& f);
             template < typename F >
             void for_each_component(F&& f) const;
+
+            std::size_t memory_usage() const noexcept override;
         private:
             registry& owner_;
             detail::sparse_map<entity_id, T, entity_id_indexer> components_;
@@ -738,6 +751,11 @@ namespace ecs_hpp
                 f(id, components_.get(id));
             }
         }
+
+        template < typename T >
+        std::size_t component_storage<T>::memory_usage() const noexcept {
+            return components_.memory_usage();
+        }
     }
 }
 
@@ -1234,6 +1252,15 @@ namespace ecs_hpp
         void process_systems_above(priority_t min);
         void process_systems_below(priority_t max);
         void process_systems_in_range(priority_t min, priority_t max);
+
+        struct memory_usage_info {
+            std::size_t entities{0u};
+            std::size_t components{0u};
+        };
+        memory_usage_info memory_usage() const noexcept;
+
+        template < typename T >
+        std::size_t component_memory_usage() const noexcept;
     private:
         template < typename T >
         detail::component_storage<T>* find_storage_() noexcept;
@@ -2217,6 +2244,24 @@ namespace ecs_hpp
         }
     }
 
+    inline registry::memory_usage_info registry::memory_usage() const noexcept {
+        memory_usage_info info;
+        info.entities += free_entity_ids_.capacity() * sizeof(free_entity_ids_[0]);
+        info.entities += entity_ids_.memory_usage();
+        for ( const auto family_id : storages_ ) {
+            info.components += storages_.get(family_id)->memory_usage();
+        }
+        return info;
+    }
+
+    template < typename T >
+    std::size_t registry::component_memory_usage() const noexcept {
+        const detail::component_storage<T>* storage = find_storage_<T>();
+        return storage
+            ? storage->memory_usage()
+            : 0u;
+    }
+
     template < typename T >
     detail::component_storage<T>* registry::find_storage_() noexcept {
         const auto family = detail::type_family<T>::id();
diff --git a/ecs_tests.cpp b/ecs_tests.cpp
index 9299464..0f6c56b 100644
--- a/ecs_tests.cpp
+++ b/ecs_tests.cpp
@@ -1154,6 +1154,79 @@ TEST_CASE("registry") {
             REQUIRE(e2.get_component<component_n>().i == 5);
         }
     }
+    SECTION("memory_usage") {
+        {
+            ecs::registry w;
+            REQUIRE(w.memory_usage().entities == 0u);
+
+            auto e1 = w.create_entity();
+            auto e2 = w.create_entity();
+
+            const std::size_t expected_usage =
+                2 * sizeof(ecs::entity_id) + // vector free entity ids
+                4 * sizeof(std::size_t) +    // sparse entity ids (keys)
+                2 * sizeof(ecs::entity_id);  // sparse entity ids (values)
+            REQUIRE(w.memory_usage().entities == expected_usage);
+
+            e1.destroy();
+            e2.destroy();
+            REQUIRE(w.memory_usage().entities == expected_usage);
+
+            e1 = w.create_entity();
+            e2 = w.create_entity();
+            REQUIRE(w.memory_usage().entities == expected_usage);
+        }
+        {
+            ecs::registry w;
+
+            auto e1 = w.create_entity();
+            e1.assign_component<position_c>(1, 2);
+
+            auto e2 = w.create_entity();
+            e2.assign_component<position_c>(1, 2);
+
+            const std::size_t expected_usage =
+                2 * sizeof(position_c) +    // vector values
+                4 * sizeof(std::size_t) +   // sparse keys (keys)
+                2 * sizeof(ecs::entity_id); // sparse keys (values)
+            REQUIRE(w.memory_usage().components == expected_usage);
+
+            REQUIRE(w.component_memory_usage<position_c>() ==
+                2 * sizeof(position_c) +
+                4 * sizeof(std::size_t) +
+                2 * sizeof(ecs::entity_id));
+
+            REQUIRE_FALSE(w.component_memory_usage<velocity_c>());
+        }
+        {
+            ecs::registry w;
+
+            auto e1 = w.create_entity();
+            e1.assign_component<position_c>(1, 2);
+
+            auto e2 = w.create_entity();
+            e2.assign_component<velocity_c>(3, 4);
+
+            const std::size_t expected_usage =
+                sizeof(position_c) +
+                2 * sizeof(std::size_t) +
+                1 * sizeof(ecs::entity_id) +
+                sizeof(velocity_c) +
+                3 * sizeof(std::size_t) +
+                1 * sizeof(ecs::entity_id);
+            REQUIRE(w.memory_usage().components == expected_usage);
+
+            REQUIRE(w.component_memory_usage<position_c>() ==
+                sizeof(position_c) +
+                2 * sizeof(std::size_t) +
+                1 * sizeof(ecs::entity_id));
+
+            REQUIRE(w.component_memory_usage<velocity_c>() ==
+                sizeof(velocity_c) +
+                3 * sizeof(std::size_t) +
+                1 * sizeof(ecs::entity_id));
+        }
+    }
 }
 
 TEST_CASE("example") {