From b2dbcb55e2832c373fecb4033a3ed77e5dbc77aa Mon Sep 17 00:00:00 2001
From: Dominick Allen <djallen@librehumanitas.org>
Date: Mon, 21 Oct 2024 12:49:43 -0500
Subject: Add vector and option.

---
 include/fud_algorithm.hpp |  36 ++-
 include/fud_array.hpp     |  10 +-
 include/fud_memory.hpp    |  16 ++
 include/fud_option.hpp    | 229 +++++++++++++++++
 include/fud_span.hpp      |  10 +-
 include/fud_status.hpp    |  66 ++---
 include/fud_vector.hpp    | 628 +++++++++++++++++++++++++++++++++++++++++++++-
 7 files changed, 939 insertions(+), 56 deletions(-)
 create mode 100644 include/fud_option.hpp

(limited to 'include')

diff --git a/include/fud_algorithm.hpp b/include/fud_algorithm.hpp
index e3d5d3b..0ad71d5 100644
--- a/include/fud_algorithm.hpp
+++ b/include/fud_algorithm.hpp
@@ -18,11 +18,11 @@
 #ifndef FUD_ALGORITHM_HPP
 #define FUD_ALGORITHM_HPP
 
+#include "fud_option.hpp"
 #include "fud_span.hpp"
 
 #include <concepts>
 #include <limits>
-#include <optional>
 #include <type_traits>
 
 namespace fud {
@@ -48,30 +48,41 @@ class Iota {
     {
     }
 
-    constexpr std::optional<T> operator()() noexcept
+    constexpr Iota(const Iota& rhs) noexcept = default;
+
+    constexpr Iota(Iota&& rhs) noexcept = default;
+
+    ~Iota() noexcept = default;
+
+    Iota& operator=(const Iota& rhs) = default;
+
+    Iota& operator=(Iota&& rhs) = default;
+
+    constexpr Option<T> operator()() noexcept
     {
         auto value = m_value;
         if (m_increment > 0) {
             if (m_limit - m_increment < m_value) {
-                return std::nullopt;
+                return NullOpt;
             }
         } else {
             if (m_limit + m_increment + 1 >= m_value) {
-                return std::nullopt;
+                return NullOpt;
             }
         }
         m_value += m_increment;
         return value;
     }
 
-    void set(T value) {
+    void set(T value)
+    {
         m_value = value;
     }
 
   private:
     T m_value;
-    const T m_increment;
-    const T m_limit;
+    T m_increment;
+    T m_limit;
 };
 
 template <typename T, size_t Size, typename Func>
@@ -91,18 +102,19 @@ Span<T, Size> mapTo(Span<T, Size> input, Span<U, Size> output, Func&& mapFunc)
         output[idx] = std::forward<Func>(mapFunc)(input[idx]);
     }
 
-    return input;
+    return output;
 }
 
-template <typename T, size_t Size, typename Func, typename Builder, typename Output>
+template <typename T, size_t Size, typename Func, typename Builder>
 auto map(Span<T, Size> input, Func&& mapFunc, Builder&& builder) -> decltype(std::forward<Builder>(builder)())
 {
+    using Output = decltype(std::forward<Builder>(builder)());
     Output output{std::forward<Builder>(builder)()};
     for (auto idx = 0; idx < input.size() && idx < output.size(); ++idx) {
         output[idx] = std::forward<Func>(mapFunc)(input[idx]);
     }
 
-    return input;
+    return output;
 }
 
 template <typename Generator, typename Builder>
@@ -132,7 +144,7 @@ bool allOf(Generator&& generator, Func&& predicate)
 {
     bool result = true;
     while (auto val = std::forward<Generator>(generator)()) {
-        result = result && std::forward<Func>(predicate)(*val);
+        result = result && std::forward<Func>(predicate)(val.value());
     }
     return result;
 }
@@ -152,7 +164,7 @@ bool anyOf(Generator&& generator, Func&& predicate)
 {
     bool result = false;
     while (auto val = std::forward<Generator>(generator)()) {
-        result = result || std::forward<Func>(predicate)(*val);
+        result = result || std::forward<Func>(predicate)(val.value());
     }
     return result;
 }
diff --git a/include/fud_array.hpp b/include/fud_array.hpp
index 807621a..dcbd54a 100644
--- a/include/fud_array.hpp
+++ b/include/fud_array.hpp
@@ -18,9 +18,10 @@
 #ifndef FUD_ARRAY_HPP
 #define FUD_ARRAY_HPP
 
-#include <cstddef>
-
 #include "fud_memory.hpp"
+#include "fud_span.hpp"
+
+#include <cstddef>
 
 namespace fud {
 
@@ -106,6 +107,11 @@ struct Array {
     constexpr bool operator==(const Array<T, Size>&) const noexcept = default;
 
     constexpr auto operator<=>(const Array<T, Size>& other) const noexcept = default;
+
+    Span<T, Size> span()
+    {
+        return Span<T, Size>{data(), Size};
+    }
 };
 
 } // namespace fud
diff --git a/include/fud_memory.hpp b/include/fud_memory.hpp
index 97328a9..6ce6312 100644
--- a/include/fud_memory.hpp
+++ b/include/fud_memory.hpp
@@ -57,6 +57,22 @@ constexpr void setMemory(Container<T, Size>& container, const T& value)
     }
 }
 
+template <template <class, size_t> class Container, typename T, size_t Size>
+constexpr void setMemory(Container<T, Size>& container, T&& value)
+{
+    for (auto& elt : container) {
+        elt = value;
+    }
+}
+
+template <template <size_t> class Container, typename T, size_t Size>
+constexpr void setMemory(Container<Size>& container, T&& value)
+{
+    for (auto& elt : container) {
+        elt = value;
+    }
+}
+
 template <size_t Count, typename T, typename U>
 void copyMem(T& destination, const U& source)
 {
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
diff --git a/include/fud_span.hpp b/include/fud_span.hpp
index 5b8497e..ed4bcc7 100644
--- a/include/fud_span.hpp
+++ b/include/fud_span.hpp
@@ -18,7 +18,6 @@
 #ifndef FUD_SPAN_HPP
 #define FUD_SPAN_HPP
 
-#include "fud_array.hpp"
 #include "fud_result.hpp"
 #include "fud_status.hpp"
 
@@ -27,11 +26,17 @@
 
 namespace fud {
 
+template <typename T, size_t Size>
+struct Array;
+
 template <typename T, size_t Size = SIZE_MAX>
 struct Span {
     static_assert(Size > 0);
     using ValueType = T;
 
+    T* m_data;
+    const size_t m_size;
+
     static Span make(Array<T, Size>& array)
     {
         Span<T, Size> output{array.data(), Size};
@@ -89,9 +94,6 @@ struct Span {
         return output;
     }
 
-    T* m_data;
-    const size_t m_size;
-
     [[nodiscard]] constexpr size_t size() const
     {
         if constexpr (Size < SIZE_MAX) {
diff --git a/include/fud_status.hpp b/include/fud_status.hpp
index 91048ac..d57a9c5 100644
--- a/include/fud_status.hpp
+++ b/include/fud_status.hpp
@@ -23,24 +23,26 @@ namespace fud {
 enum class [[nodiscard]] FudStatus
 {
     Success = 0,
+    Partial,
+    Failure,
     NullPointer,
-    StringInvalid,
-    ObjectInvalid,
-    OperationInvalid,
-    AllocFailure,
-    DeallocFailure,
     ArgumentInvalid,
+    VariantInvalid,
+    ObjectInvalid,
     Utf8Invalid,
-    Failure,
+    StringInvalid,
+    OperationInvalid,
+    AlreadyInitialized,
+    FormatInvalid,
+    RangeError,
+    IndexInvalid,
+    Exists,
     NotFound,
-    Aliased,
     Empty,
-    Partial,
     Full,
-    RangeError,
-    VariantInvalid,
-    BadArrayLength,
-    FormatInvalid,
+    Aliased,
+    AllocFailure,
+    DeallocFailure,
     NotImplemented,
     NotSupported
 };
@@ -50,6 +52,10 @@ constexpr const char* FudStatusToString(FudStatus status)
     switch (status) {
     case FudStatus::Success:
         return "Success";
+    case FudStatus::Partial:
+        return "Partial";
+    case FudStatus::Failure:
+        return "Failure";
     case FudStatus::NullPointer:
         return "NullPointer";
     case FudStatus::StringInvalid:
@@ -58,34 +64,34 @@ constexpr const char* FudStatusToString(FudStatus status)
         return "ObjectInvalid";
     case FudStatus::OperationInvalid:
         return "OperationInvalid";
-    case FudStatus::AllocFailure:
-        return "AllocFailure";
-    case FudStatus::DeallocFailure:
-        return "DeallocFailure";
     case FudStatus::ArgumentInvalid:
         return "ArgumentInvalid";
     case FudStatus::Utf8Invalid:
         return "Utf8Invalid";
-    case FudStatus::Failure:
-        return "Failure";
-    case FudStatus::NotFound:
-        return "NotFound";
-    case FudStatus::Aliased:
-        return "Aliased";
-    case FudStatus::Empty:
-        return "Empty";
-    case FudStatus::Partial:
-        return "Partial";
-    case FudStatus::Full:
-        return "Full";
     case FudStatus::RangeError:
         return "RangeError";
     case FudStatus::VariantInvalid:
         return "VariantInvalid";
-    case FudStatus::BadArrayLength:
-        return "BadArrayLength";
     case FudStatus::FormatInvalid:
         return "FormatInvalid";
+    case FudStatus::AlreadyInitialized:
+        return "AlreadyInitialized";
+    case FudStatus::IndexInvalid:
+        return "IndexInvalid";
+    case FudStatus::Exists:
+        return "Exists";
+    case FudStatus::NotFound:
+        return "NotFound";
+    case FudStatus::Empty:
+        return "Empty";
+    case FudStatus::Full:
+        return "Full";
+    case FudStatus::Aliased:
+        return "Aliased";
+    case FudStatus::AllocFailure:
+        return "AllocFailure";
+    case FudStatus::DeallocFailure:
+        return "DeallocFailure";
     case FudStatus::NotImplemented:
         return "NotImplemented";
     case FudStatus::NotSupported:
diff --git a/include/fud_vector.hpp b/include/fud_vector.hpp
index 56e1659..f90819a 100644
--- a/include/fud_vector.hpp
+++ b/include/fud_vector.hpp
@@ -19,42 +19,654 @@
 #define FUD_VECTOR_HPP
 
 #include "fud_allocator.hpp"
+#include "fud_assert.hpp"
+#include "fud_config.hpp"
+#include "fud_option.hpp"
 #include "fud_result.hpp"
+#include "fud_span.hpp"
 #include "fud_status.hpp"
 
 #include <cstddef>
+#include <functional>
+#include <new> // IWYU pragma: keep (placement new)
 
 namespace fud {
 
 template <typename T>
 class Vector {
+    static constexpr size_t ElementSize = sizeof(T);
+    static constexpr size_t Alignment = alignof(T);
+
   public:
-    static Result<Vector<T>, FudStatus> from(const Vector<T>& rhs);
+    constexpr Vector() noexcept = default;
+    constexpr Vector(const Vector<T>& rhs) = delete;
+    constexpr Vector(Vector<T>&& rhs) noexcept :
+        m_allocator(rhs.m_allocator), m_data(rhs.m_data), m_length{rhs.m_length}, m_capacity{rhs.m_capacity}
+    {
+        rhs.m_allocator = nullptr;
+        rhs.m_data = nullptr;
+        rhs.m_length = 0;
+        rhs.m_capacity = 0;
+    }
+
+    ~Vector() noexcept
+    {
+        static_cast<void>(cleanup());
+    }
+
+    Vector& operator=(const Vector<T>& rhs) = delete;
+
+    Vector& operator=(Vector<T>&& rhs) noexcept
+    {
+        cleanup();
+        m_allocator = rhs.m_allocator;
+        m_data = rhs.m_data;
+        m_length = rhs.m_length;
+        m_capacity = rhs.m_length;
+
+        rhs.m_allocataor = nullptr;
+        rhs.m_data = nullptr;
+        rhs.m_length = 0;
+        rhs.m_capacity = 0;
+    }
+
+    static Result<Vector<T>, FudStatus> withCapacity(size_t capacity, Allocator* allocator = &globalFudAllocator)
+    {
+        Vector<T> output{};
+        auto status = initializeWithCapacity(output, capacity, allocator);
+        if (status != FudStatus::Success) {
+            return status;
+        }
+        return output;
+    }
+
+    static FudStatus initializeWithCapacity(
+        Vector<T>& output,
+        size_t capacity,
+        Allocator* allocator = &globalFudAllocator)
+    {
+        if (output.m_data != nullptr) {
+            return FudStatus::AlreadyInitialized;
+        }
+
+        if (allocator == nullptr) {
+            return FudStatus::NullPointer;
+        }
+
+        if (capacity > SIZE_MAX / ElementSize) {
+            return FudStatus::ArgumentInvalid;
+        }
+
+        size_t requestedSize = capacity * ElementSize;
+        auto dataPtrResult = allocator->allocate(requestedSize, Alignment);
+        if (dataPtrResult.isError()) {
+            return dataPtrResult.getError();
+        }
+
+        output.m_allocator = allocator;
+        output.m_data = static_cast<T*>(dataPtrResult.getOkay());
+        output.m_length = 0;
+        output.m_capacity = capacity;
+        return FudStatus::Success;
+    }
+
+    static Result<Vector<T>, FudStatus> withSize(size_t count, Allocator* allocator = &globalFudAllocator)
+    {
+        Vector<T> output{};
+        auto status = initializeWithCapacity(output, count, allocator);
+        if (status != FudStatus::Success) {
+            return status;
+        }
+        return output;
+    }
+
+    static Result<Vector<T>, FudStatus> initializeWithSize(
+        Vector<T>& output,
+        size_t count,
+        Allocator* allocator = &globalFudAllocator)
+    {
+        if (output.m_data != nullptr) {
+            return FudStatus::AlreadyInitialized;
+        }
+
+        auto status = Vector::initializeWithCapacity(output, count, allocator);
+        if (status != FudStatus::Success) {
+            return status;
+        }
+
+        output.m_length = count;
+        for (size_t index = 0; index < count; ++index) {
+            const auto* ptr = new (output.m_data + index) T();
+            fudAssert(ptr != nullptr);
+        }
+        return output;
+    }
+
+    template <typename Builder>
+    static Result<Vector<T>, FudStatus> withSizeFallible(
+        size_t count,
+        Builder&& builder,
+        Allocator* allocator = &globalFudAllocator)
+    {
+        Vector<T> output{};
+        auto status = initializeWithSizeFallible(output, count, std::forward<Builder>(builder), allocator);
+        if (status != FudStatus::Success) {
+            return status;
+        }
+        return output;
+    }
+
+    template <typename Builder>
+    static Result<Vector<T>, FudStatus> initializeWithSizeFallible(
+        Vector<T>& output,
+        size_t count,
+        Builder&& builder,
+        Allocator* allocator = &globalFudAllocator)
+    {
+        using BuilderResult = decltype(std::forward<Builder>(builder)());
+        static_assert(std::is_same_v<BuilderResult, FudStatus>());
+
+        auto status = Vector::initializeWithCapacity(output, count, allocator);
+        if (status != FudStatus::Success) {
+            return status;
+        }
+
+        output.m_length = count;
+
+        for (size_t index = 0; index < count; ++index) {
+            auto builderResult{std::forward<Builder>(builder)(output.m_data[index])};
+            if (builderResult.isError()) {
+                return builderResult.takeError();
+            }
+        }
+
+        return output;
+    }
 
-    static Vector<T> move(Vector<T>&& rhs);
+    static Result<Vector<T>, FudStatus> from(const Vector<T>& rhs, Option<Allocator*> allocatorOption = NullOpt)
+    {
+        Allocator* allocator = nullptr;
+        if (allocatorOption.hasValue()) {
+            allocator = allocatorOption.value();
+            if (allocator == nullptr) {
+                return FudStatus::NullPointer;
+            }
+        } else {
+            allocator = rhs.allocator;
+            if (allocator == nullptr) {
+                return FudStatus::ArgumentInvalid;
+            }
+        }
+
+        fudAssert(rhs.m_length <= rhs.m_capacity);
+
+        auto spanResult = rhs.span();
+        if (spanResult.isError()) {
+            return spanResult.takeError();
+        }
+        Vector<T> output{};
+        auto status = Vector::initializeFromSpan(output, rhs.m_length, allocator);
+        if (status != FudStatus::Success) {
+            return status;
+        }
+        return output;
+    }
+
+    template <size_t Size>
+    static Result<Vector<T>, FudStatus> from(Span<const T, Size>& rhs, Allocator* allocator)
+    {
+        Vector<T> output{};
+        auto status = initializeFromSpan(output, rhs, allocator);
+        if (status != FudStatus::Success) {
+            return status;
+        }
+        return output;
+    }
+
+    template <size_t Size>
+    static FudStatus initializeFromSpan(Vector<T>& output, Span<const T, Size>& rhs, Allocator* allocator)
+    {
+        auto status = Vector::initializeWithCapacity(output, rhs.size(), allocator);
+        if (status != FudStatus::Success) {
+            return status;
+        }
+        output.m_length = rhs.m_length;
+        for (size_t index = 0; index < output.m_length; ++index) {
+            output.m_data[index] = rhs[index];
+        }
+    }
+
+    static Vector<T> move(Vector<T>&& rhs) noexcept
+    {
+        return Vector<T>{std::move(rhs)};
+    }
 
     FudStatus copy(const Vector<T>& rhs);
 
     FudStatus take(Vector<T>&& rhs);
 
-    [[nodiscard]] size_t size() const {
+    [[nodiscard]] size_t size() const
+    {
         return m_length;
     }
 
-    [[nodiscard]] size_t capacity() const {
+    [[nodiscard]] size_t capacity() const
+    {
         return m_capacity;
     }
 
-    FudStatus reserve();
+    Result<Span<const T>, FudStatus> span() const
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        return Span{m_data, m_length};
+    }
+
+    Result<Span<T>, FudStatus> span()
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        return Span{m_data, m_length};
+    }
+
+    Result<Span<const T>, FudStatus> span(size_t count) const
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        if (count > m_length) {
+            return FudStatus::ArgumentInvalid;
+        }
+        return Span{m_data, count};
+    }
+
+    Result<Span<T>, FudStatus> span(size_t count)
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        if (count > m_length) {
+            return FudStatus::ArgumentInvalid;
+        }
+        return Span{m_data, count};
+    }
+
+    Result<Span<const T>, FudStatus> span(size_t start, size_t count) const
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        if (SIZE_MAX - start < m_length || start + count > m_length) {
+            return FudStatus::ArgumentInvalid;
+        }
+        return Span{m_data + start, count};
+    }
+
+    Result<Span<T>, FudStatus> span(size_t start, size_t count)
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        if (SIZE_MAX - start < m_length || start + count > m_length) {
+            return FudStatus::ArgumentInvalid;
+        }
+        return Span{m_data + start, count};
+    }
+
+    FudStatus reserve(size_t count)
+    {
+        if (count <= m_capacity) {
+            return FudStatus::Success;
+        }
+
+        if (m_allocator == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+
+        if (count > SIZE_MAX / ElementSize) {
+            return FudStatus::ArgumentInvalid;
+        }
+
+        size_t requestedSize = count * ElementSize;
+        auto dataPtrResult = m_allocator->allocate(requestedSize, Alignment);
+        if (dataPtrResult.isError()) {
+            return dataPtrResult.takeError();
+        }
+
+        auto* dataPtr = static_cast<T*>(dataPtrResult.takeOkay());
+        for (size_t index = 0; index < m_length; ++index) {
+            const auto* ptr = new (dataPtr + index) T(std::move(m_data[index]));
+            fudAssert(ptr != nullptr);
+            m_data[index].~T();
+        }
+
+        m_data = dataPtr;
+        m_capacity = count;
+
+        return FudStatus::Success;
+    }
+
+    FudStatus resize(size_t count)
+    {
+        if (count == m_length) {
+            return FudStatus::Success;
+        }
+
+        if (m_allocator == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
 
-    FudStatus resize();
+        if (count < m_length) {
+            for (size_t index = count; index < m_length; ++index) {
+                m_data[index].~T();
+            }
+            m_length = count;
+            return FudStatus::Success;
+        }
 
-    FudStatus clear();
+        auto reserveStatus = reserve(count);
+        if (reserveStatus != FudStatus::Success) {
+            return reserveStatus;
+        }
 
-    // FudResult at();
+        for (size_t index = m_length; index < count; ++index) {
+            const auto* ptr = new (m_data + index) T();
+            fudAssert(ptr != nullptr);
+        }
+
+        m_length = count;
+        return FudStatus::Success;
+    }
+
+    FudStatus clear()
+    {
+        if (m_allocator == nullptr || m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        for (size_t index = 0; index < m_length; ++index) {
+            m_data[index].~T();
+        }
+        m_length = 0;
+        return FudStatus::Success;
+    }
+
+    Result<std::reference_wrapper<T>, FudStatus> get(size_t index)
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        if (index >= m_length) {
+            return FudStatus::IndexInvalid;
+        }
+        return std::ref(m_data[index]);
+    }
+
+    Result<const std::reference_wrapper<const T>, FudStatus> ref(size_t index) const
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        if (index >= m_length) {
+            return FudStatus::IndexInvalid;
+        }
+        return std::cref(m_data[index]);
+    }
+
+    constexpr Option<T&> front()
+    {
+        if (m_length > 0) {
+            fudAssert(m_data != nullptr);
+            return m_data[0];
+        }
+        return NullOpt;
+    }
+
+    constexpr Option<const T&> front() const
+    {
+        if (m_length > 0) {
+            fudAssert(m_data != nullptr);
+            return m_data[0];
+        }
+        return NullOpt;
+    }
+
+    constexpr Option<T&> back()
+    {
+        if (m_length > 0) {
+            fudAssert(m_data != nullptr);
+            return m_data[m_length - 1];
+        }
+        return NullOpt;
+    }
+
+    constexpr Option<const T&> back() const
+    {
+        if (m_length > 0) {
+            return m_data[m_length - 1];
+        }
+        return NullOpt;
+    }
+
+    constexpr T* data() noexcept
+    {
+        return m_data;
+    }
+
+    constexpr const T* data() const noexcept
+    {
+        return m_data;
+    }
+
+    constexpr T* begin() noexcept
+    {
+        return m_data;
+    }
+
+    constexpr const T* begin() const noexcept
+    {
+        return m_data;
+    }
+
+    constexpr T* end() noexcept
+    {
+        return m_data + m_length;
+    }
+
+    constexpr const T* end() const noexcept
+    {
+        return m_data + m_length;
+    }
+
+    constexpr T& operator[](size_t index)
+    {
+        if constexpr (fudBoundsChecking) {
+            fudAssert(m_data != nullptr);
+            fudAssert(index < m_length);
+        }
+        return m_data[index];
+    }
+
+    constexpr const T& operator[](size_t index) const
+    {
+        if constexpr (fudBoundsChecking) {
+            fudAssert(m_data != nullptr);
+            fudAssert(index < m_length);
+        }
+        return m_data[index];
+    }
+
+    FudStatus pushBack(const T& value)
+    {
+        if (m_length == m_capacity) {
+            auto status = grow();
+            if (status != FudStatus::Success) {
+                return status;
+            }
+        }
+        const auto* ptr = new (m_data + m_length) T(value);
+        fudAssert(ptr != nullptr);
+        m_length++;
+        return FudStatus::Success;
+    }
+
+    FudStatus pushBack(T&& value)
+    {
+        if (m_length == m_capacity) {
+            auto status = grow();
+            if (status != FudStatus::Success) {
+                return status;
+            }
+        }
+        const auto* ptr = new (m_data + m_length) T(std::move(value));
+        fudAssert(ptr != nullptr);
+        m_length++;
+        return FudStatus::Success;
+    }
+
+    Result<T, FudStatus> popBack()
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        if (m_length == 0) {
+            return FudStatus::Empty;
+        }
+        auto result{std::move(m_data[m_length - 1])};
+        m_length--;
+        m_data[m_length].~T();
+        return result;
+    }
+
+    FudStatus eraseBack()
+    {
+        if (m_data == nullptr) {
+            return FudStatus::ObjectInvalid;
+        }
+        if (m_length == 0) {
+            return FudStatus::Empty;
+        }
+        m_length--;
+        m_data[m_length].~T();
+        return FudStatus::Success;
+    }
+
+    FudStatus insert(size_t index, const T& value)
+    {
+        if (index > m_length) {
+            return FudStatus::IndexInvalid;
+        }
+        if (index == m_length) {
+            return pushBack(value);
+        }
+        if (m_length == m_capacity) {
+            auto status = grow();
+            if (status != FudStatus::Success) {
+                return status;
+            }
+        }
+
+        const auto* ptr = new (m_data + m_length) T(std::move(m_data[m_length - 1]));
+        fudAssert(ptr != nullptr);
+
+        for (size_t backIndex = m_length - 1; backIndex > index; --backIndex) {
+            m_data[backIndex] = std::move(m_data[backIndex - 1]);
+        }
+        m_data[index] = value;
+        m_length++;
+        return FudStatus::Success;
+    }
+
+    FudStatus insert(size_t index, T&& value)
+    {
+        if (index > m_length) {
+            return FudStatus::IndexInvalid;
+        }
+        if (index == m_length) {
+            return pushBack(std::move(value));
+        }
+        if (m_length == m_capacity) {
+            auto status = grow();
+            if (status != FudStatus::Success) {
+                return status;
+            }
+        }
+
+        const auto* ptr = new (m_data + m_length) T(std::move(m_data[m_length - 1]));
+        fudAssert(ptr != nullptr);
+
+        for (size_t backIndex = m_length - 1; backIndex > index; --backIndex) {
+            m_data[backIndex] = std::move(m_data[backIndex - 1]);
+        }
+        m_data[index] = std::move(value);
+        m_length++;
+        return FudStatus::Success;
+    }
+
+    FudStatus erase(size_t index)
+    {
+        if (index >= m_length) {
+            return FudStatus::IndexInvalid;
+        }
+
+        m_data[index].~T();
+        for (size_t fwdIndex = index; fwdIndex + 1 < m_length; fwdIndex++)
+        {
+            m_data[fwdIndex] = std::move(m_data[fwdIndex + 1]);
+        }
+        m_data[m_length - 1].~T();
+        m_length--;
+        return FudStatus::Success;
+    }
 
   private:
+    FudStatus grow()
+    {
+        // See https://github.com/facebook/folly/blob/main/folly/docs/FBVector.md
+        size_t additional = m_capacity < 2 ? 1 : m_capacity / 2;
+        if (SIZE_MAX - additional * ElementSize < m_capacity * ElementSize) {
+            additional = SIZE_MAX - m_capacity * ElementSize / 2;
+        }
+        while (additional > 0) {
+            auto reserveStatus = reserve(additional + m_capacity);
+            if (reserveStatus == FudStatus::Success) {
+                break;
+            }
+            if (reserveStatus == FudStatus::AllocFailure) {
+                additional /= 2;
+            } else {
+                return reserveStatus;
+            }
+        }
+
+        if (m_length == m_capacity) {
+            return FudStatus::AllocFailure;
+        }
+
+        return FudStatus::Success;
+    }
+
+    FudStatus cleanup() noexcept
+    {
+        auto status = clear();
+
+        if (m_data != nullptr && m_allocator != nullptr) {
+            auto deallocStatus = m_allocator->deallocate(m_data, m_capacity);
+            if (status == FudStatus::Success) {
+                status = deallocStatus;
+            }
+        }
+
+        m_allocator = nullptr;
+        m_data = nullptr;
+        m_length = 0;
+        m_capacity = 0;
+        return status;
+    }
+
     Allocator* m_allocator{&globalFudAllocator};
+    T* m_data{nullptr};
     size_t m_length{0};
     size_t m_capacity{0};
 };
-- 
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