From acd75ffe1ca1e2df782ad9d1b893bfd40e9d050e Mon Sep 17 00:00:00 2001
From: Michele Caini <michele.caini@gmail.com>
Date: Thu, 30 Sep 2021 16:34:09 +0200
Subject: [PATCH] iterator: added utility input_iterator_proxy

---
 src/entt/core/iterator.hpp  | 43 +++++++++++++++++++++++++++++++++++++
 src/entt/entt.hpp           |  1 +
 test/CMakeLists.txt         |  1 +
 test/entt/core/iterator.cpp | 13 +++++++++++
 4 files changed, 58 insertions(+)
 create mode 100644 src/entt/core/iterator.hpp
 create mode 100644 test/entt/core/iterator.cpp

diff --git a/src/entt/core/iterator.hpp b/src/entt/core/iterator.hpp
new file mode 100644
index 000000000..f0370ea5e
--- /dev/null
+++ b/src/entt/core/iterator.hpp
@@ -0,0 +1,43 @@
+#ifndef ENTT_CORE_ITERATOR_HPP
+#define ENTT_CORE_ITERATOR_HPP
+
+#include <memory>
+#include "../config/config.h"
+
+namespace entt {
+
+/**
+ * @brief Helper type to use as pointer with input iterators.
+ * @tparam Type of wrapped value.
+ */
+template<typename Type>
+struct input_iterator_proxy {
+    /**
+     * @brief Constructs a proxy object from a given value.
+     * @param val Value to use to initialize the proxy object.
+     */
+    input_iterator_proxy(Type &&val)
+        : value{std::forward<Type>(val)} {}
+
+    /**
+     * @brief Access operator for accessing wrapped values.
+     * @return A pointer to the wrapped value.
+     */
+    Type *operator->() ENTT_NOEXCEPT {
+        return std::addressof(value);
+    }
+
+private:
+    Type value;
+};
+
+/**
+ * @brief Deduction guide.
+ * @tparam Type Type of wrapped value.
+ */
+template<typename Type>
+input_iterator_proxy(Type &&) -> input_iterator_proxy<Type>;
+
+} // namespace entt
+
+#endif
diff --git a/src/entt/entt.hpp b/src/entt/entt.hpp
index 64b18b19d..1c9077f1e 100644
--- a/src/entt/entt.hpp
+++ b/src/entt/entt.hpp
@@ -7,6 +7,7 @@
 #include "core/family.hpp"
 #include "core/hashed_string.hpp"
 #include "core/ident.hpp"
+#include "core/iterator.hpp"
 #include "core/memory.hpp"
 #include "core/monostate.hpp"
 #include "core/tuple.hpp"
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index b56e3385a..f15fab825 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -168,6 +168,7 @@ SETUP_BASIC_TEST(enum entt/core/enum.cpp)
 SETUP_BASIC_TEST(family entt/core/family.cpp)
 SETUP_BASIC_TEST(hashed_string entt/core/hashed_string.cpp)
 SETUP_BASIC_TEST(ident entt/core/ident.cpp)
+SETUP_BASIC_TEST(iterator entt/core/iterator.cpp)
 SETUP_BASIC_TEST(memory entt/core/memory.cpp)
 SETUP_BASIC_TEST(monostate entt/core/monostate.cpp)
 SETUP_BASIC_TEST(tuple entt/core/tuple.cpp)
diff --git a/test/entt/core/iterator.cpp b/test/entt/core/iterator.cpp
new file mode 100644
index 000000000..cb4f8bafc
--- /dev/null
+++ b/test/entt/core/iterator.cpp
@@ -0,0 +1,13 @@
+#include <gtest/gtest.h>
+#include <entt/core/iterator.hpp>
+
+struct clazz {
+    int value{0};
+};
+
+TEST(Iterator, InputIteratorProxy) {
+    entt::input_iterator_proxy proxy{clazz{}};
+    proxy->value = 42;
+
+    ASSERT_EQ(proxy->value, 42);
+}