From 9da862db50fc8892315b803c17139497780c357b Mon Sep 17 00:00:00 2001
From: Alexis Placet <alexis.placet@quantstack.net>
Date: Thu, 4 Apr 2024 12:00:16 +0200
Subject: [PATCH] Add value_ptr

---
 CMakeLists.txt             |   3 +-
 include/sparrow/memory.hpp |  83 ++++++++++++++++++++++++++++
 test/CMakeLists.txt        |   1 +
 test/test_memory.cpp       | 109 +++++++++++++++++++++++++++++++++++++
 4 files changed, 195 insertions(+), 1 deletion(-)
 create mode 100644 include/sparrow/memory.hpp
 create mode 100644 test/test_memory.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 076713b7..f89bc08b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,10 +52,11 @@ OPTION(BUILD_TESTS "sparrow test suite" OFF)
 set(SPARROW_HEADERS
     ${SPARROW_INCLUDE_DIR}/sparrow/array_data.hpp
     ${SPARROW_INCLUDE_DIR}/sparrow/buffer.hpp
-    ${SPARROW_INCLUDE_DIR}/sparrow/fixed_size_layout.hpp
     ${SPARROW_INCLUDE_DIR}/sparrow/data_type.hpp
     ${SPARROW_INCLUDE_DIR}/sparrow/dynamic_bitset.hpp
+    ${SPARROW_INCLUDE_DIR}/sparrow/fixed_size_layout.hpp
     ${SPARROW_INCLUDE_DIR}/sparrow/iterator.hpp
+    ${SPARROW_INCLUDE_DIR}/sparrow/memory.hpp
     ${SPARROW_INCLUDE_DIR}/sparrow/mp_utils.hpp
     ${SPARROW_INCLUDE_DIR}/sparrow/sparrow_version.hpp
     ${SPARROW_INCLUDE_DIR}/sparrow/variable_size_binary_layout.hpp
diff --git a/include/sparrow/memory.hpp b/include/sparrow/memory.hpp
new file mode 100644
index 00000000..399ffab3
--- /dev/null
+++ b/include/sparrow/memory.hpp
@@ -0,0 +1,83 @@
+#include <stdexcept>
+#include <memory>
+
+namespace sparrow {
+
+template <class T>
+class value_ptr {
+public:
+    value_ptr() = default;
+
+    explicit value_ptr(T value)
+        : value_(std::make_unique<T>(std::move(value))) {}
+
+    value_ptr(const value_ptr& other)
+        : value_(other.value_ ? std::make_unique<T>(*other.value_) : std::unique_ptr<T>()){}
+
+    value_ptr(value_ptr&& other) noexcept
+        : value_(std::move(other.value_)) {
+        other.reset();
+    }
+
+    value_ptr& operator=(const value_ptr& other) {
+        if (other.has_value()) {
+            value_ = std::make_unique<T>(*other.value_);
+        }else {
+            value_.reset();
+        }
+        return *this;
+    }
+
+    value_ptr& operator=(value_ptr&& other) noexcept {
+        if (this != &other) {
+            value_ = std::move(other.value_);
+            other.reset();
+        }
+        return *this;
+    }
+
+    T& operator*() {
+        if (!value_) {
+            throw std::runtime_error("No value stored in value_ptr");
+        }
+        return *value_;
+    }
+
+    const T& operator*() const {
+        if (!value_) {
+            throw std::runtime_error("No value stored in value_ptr");
+        }
+        return *value_;
+    }
+
+    T* operator->() {
+        if (!value_) {
+            throw std::runtime_error("No value stored in value_ptr");
+        }
+        return &*value_;
+    }
+
+    const T* operator->() const {
+        if (!value_) {
+            throw std::runtime_error("No value stored in value_ptr");
+        }
+        return &*value_;
+    }
+
+    explicit operator bool() const noexcept {
+        return has_value();
+    }
+
+    bool has_value() const noexcept {
+        return bool(value_);
+    }
+
+    void reset() noexcept {
+        value_.reset();
+    }
+
+private:
+    std::unique_ptr<T> value_;
+};
+
+}
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index c7b7caca..0a196bf6 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -42,6 +42,7 @@ set(SPARROW_TESTS_SOURCES
     test_layout.cpp
     test_variable_size_binary_layout.cpp
     test_dictionary_encoded_layout.cpp
+    test_memory.cpp
 )
 set(test_target "test_sparrow_lib")
 add_executable(${test_target} ${SPARROW_TESTS_SOURCES})
diff --git a/test/test_memory.cpp b/test/test_memory.cpp
new file mode 100644
index 00000000..7c15163e
--- /dev/null
+++ b/test/test_memory.cpp
@@ -0,0 +1,109 @@
+#include <functional>
+
+#include "sparrow/memory.hpp"
+
+#include "doctest/doctest.h"
+
+using namespace sparrow;
+
+TEST_SUITE("value_ptr")
+{
+    TEST_CASE("constructor")
+    {
+        value_ptr<int> vp;
+        CHECK(!vp);
+
+        value_ptr vp1(42);
+        REQUIRE(vp1);
+        CHECK(*vp1 == 42);
+    }
+
+    TEST_CASE("copy constructor")
+    {
+        value_ptr vp1(42);
+        value_ptr vp2(vp1);
+        REQUIRE(vp1);
+        REQUIRE(vp2);
+        CHECK(*vp1 == 42);
+        CHECK(*vp2 == 42);
+    }
+
+    TEST_CASE("copy")
+    {
+        value_ptr vp1(42);
+        value_ptr vp2 = vp1;
+        REQUIRE(vp1);
+        REQUIRE(vp2);
+        CHECK(*vp1 == 42);
+        CHECK(*vp2 == 42);
+    }
+
+    TEST_CASE("move constructor")
+    {
+        value_ptr vp1(42);
+        value_ptr vp2(std::move(vp1));
+        CHECK(!vp1);
+        REQUIRE(vp2);
+        CHECK(*vp2 == 42);
+    }
+
+    TEST_CASE("move assignment")
+    {
+        value_ptr vp1(42);
+        value_ptr<int> vp2;
+        vp2 = std::move(vp1);
+        CHECK(!vp1);
+        REQUIRE(vp2);
+        CHECK(*vp2 == 42);
+
+        value_ptr<int> vp3;
+        {
+            value_ptr vp4(43);
+            vp3 = std::move(vp4);
+        }
+        REQUIRE(vp3);
+        CHECK(*vp3 == 43);
+    }
+
+    TEST_CASE("operator*")
+    {
+        value_ptr vp(42);
+        CHECK(*vp == 42);
+
+        *vp = 43;
+        CHECK(*vp == 43);
+    }
+
+    TEST_CASE("operator->")
+    {
+        value_ptr vp(std::vector<int>{42});
+        CHECK(vp.operator->() == &*vp);
+        CHECK(vp->size() == 1);
+    }
+
+    TEST_CASE("operator bool")
+    {
+        value_ptr<int> vp;
+        CHECK(!vp);
+
+        value_ptr vp1(42);
+        CHECK(vp1);
+    }
+
+    TEST_CASE("has_value")
+    {
+        value_ptr<int> vp;
+        CHECK(!vp.has_value());
+
+        value_ptr vp1(42);
+        CHECK(vp1.has_value());
+    }
+
+    TEST_CASE("reset")
+    {
+        value_ptr vp(42);
+        REQUIRE(vp);
+        vp.reset();
+        CHECK(!vp);
+    }
+}