Add vector and option.

1 files changed, 229 insertions, 0 deletions

diff --git a/include/fud_option.hpp b/include/fud_option.hpp
new file mode 100644
index 0000000..ca3954f
--- /dev/null
+++ b/include/fud_option.hpp
@@ -0,0 +1,229 @@
+/*
+ * libfud
+ * Copyright 2024 Dominick Allen
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FUD_OPTION_HPP
+#define FUD_OPTION_HPP
+
+#include "fud_assert.hpp"
+
+#include <cstddef>
+#include <functional>
+#include <new> // IWYU pragma: keep (placement new)
+#include <type_traits>
+
+namespace fud {
+
+namespace option_detail {
+
+struct NullOptionType {
+    enum class NullOptConstructor : char
+    {
+        Monostate
+    };
+
+    constexpr explicit NullOptionType(NullOptConstructor /*unnamed*/)
+    {
+    }
+};
+
+template <size_t Size>
+struct DataArray {
+    // NOLINTBEGIN(cppcoreguidelines-avoid-c-arrays)
+    std::byte m_data[Size];
+    // NOLINTEND(cppcoreguidelines-avoid-c-arrays)
+
+    constexpr std::byte* data() noexcept
+    {
+        return m_data;
+    }
+
+    [[nodiscard]] constexpr const std::byte* data() const noexcept
+    {
+        return m_data;
+    }
+
+    constexpr bool operator==(const DataArray&) const noexcept = default;
+
+    constexpr void clear()
+    {
+        for (size_t idx = 0; idx < Size; ++idx) {
+            m_data[idx] = std::byte(0);
+        }
+    }
+};
+
+} // namespace option_detail
+
+inline constexpr option_detail::NullOptionType NullOpt{option_detail::NullOptionType::NullOptConstructor::Monostate};
+
+template <typename T>
+class Option {
+  private:
+    static_assert(!std::is_same_v<T, option_detail::NullOptionType>);
+    static constexpr bool IsRef = std::is_reference_v<T>;
+    using ValueType = typename std::remove_reference<T>::type;
+    static constexpr size_t Size = IsRef ? sizeof(std::reference_wrapper<ValueType>) : sizeof(ValueType);
+
+  public:
+    constexpr Option() noexcept : m_engaged{false}
+    {
+    }
+
+    constexpr Option(option_detail::NullOptionType nullOpt) noexcept : m_engaged{false}
+    {
+        static_cast<void>(nullOpt);
+    }
+
+    constexpr Option(T value) noexcept : m_engaged{true}
+    {
+        if constexpr (IsRef) {
+            new (m_data.data()) std::reference_wrapper<ValueType>(std::ref(value));
+            if (!m_engaged) {
+                std::abort();
+            }
+        } else {
+            new (m_data.data()) ValueType(value);
+            if (!m_engaged) {
+                std::abort();
+            }
+        }
+    }
+
+    constexpr Option(const Option& rhs) noexcept : m_engaged(rhs.m_engaged), m_data(rhs.m_data)
+    {
+    }
+
+    constexpr Option(Option&& rhs) noexcept : m_engaged(rhs.m_engaged), m_data(std::move(rhs.m_data))
+    {
+        rhs.cleanup();
+    }
+
+    ~Option() noexcept
+    {
+        destroy();
+    }
+
+    Option& operator=(const Option& rhs) noexcept
+    {
+        if (&rhs == this) {
+            return *this;
+        }
+        destroy();
+        m_engaged = rhs.m_engaged;
+        m_data = rhs.m_data;
+        return *this;
+    }
+
+    Option& operator=(Option&& rhs) noexcept
+    {
+        destroy();
+        m_engaged = rhs.m_engaged;
+        m_data = std::move(rhs.m_data);
+        rhs.cleanup();
+        return *this;
+    }
+
+    [[nodiscard]] bool hasValue() const
+    {
+        return m_engaged;
+    }
+
+    operator bool() const {
+        return hasValue();
+    }
+
+    [[nodiscard]] constexpr const ValueType& value() const&
+    {
+        fudAssert(m_engaged);
+        if constexpr (IsRef) {
+            return *reinterpret_cast<const std::reference_wrapper<ValueType>*>(m_data.data());
+        } else {
+            return *reinterpret_cast<const ValueType*>(m_data.data());
+        }
+    }
+
+    [[nodiscard]] constexpr ValueType& value() &
+    {
+        fudAssert(m_engaged);
+        if constexpr (IsRef) {
+            return *reinterpret_cast<std::reference_wrapper<ValueType>*>(m_data.data());
+        } else {
+            return *reinterpret_cast<ValueType*>(m_data.data());
+        }
+    }
+
+    [[nodiscard]] constexpr const ValueType&& value() const&&
+    {
+        fudAssert(m_engaged);
+        static_assert(!IsRef);
+        return *reinterpret_cast<const ValueType*>(m_data.data());
+    }
+
+    template <typename F>
+    constexpr auto map(F&& func) const & -> Option<decltype(std::forward<F>(func)(value()))>
+    {
+        using U = decltype(std::forward<F>(func)(value()));
+        // static_assert(std::is_same_v<decltype(std::forward<F>(func)(value())), Option<U>>());
+        if (hasValue()) {
+            return Option<U>{std::forward<F>(func)(value())};
+        }
+        return Option<U>{NullOpt};
+    }
+
+  private:
+    constexpr void destroy() noexcept
+    {
+        if (m_engaged) {
+            if constexpr (IsRef) {
+                // reinterpret_cast<std::reference_wrapper<ValueType>*>(m_data.data());
+            } else {
+                reinterpret_cast<ValueType*>(m_data.data())->~ValueType();
+            }
+            cleanup();
+        }
+    }
+
+    constexpr void cleanup() noexcept
+    {
+        m_engaged = false;
+        m_data.clear();
+    }
+
+    // alignas(maxAlign) Array<uint8_t, maxSize> priv_m_data;
+
+    alignas(alignof(T)) option_detail::DataArray<Size> m_data{};
+
+    bool m_engaged;
+};
+
+namespace test {
+
+void testOption()
+{
+    Option<int> intOpt;
+    static_cast<void>(intOpt);
+    Option<int&> intRefNull;
+    static_cast<void>(intRefNull);
+    int value;
+    Option<int&> intRefValue{value};
+}
+
+} // namespace test
+
+} // namespace fud
+
+#endif