Added MemoryView.

source/mijin/container/memory_view.hpp

@@ -0,0 +1,84 @@
+
+#pragma once
+
+#if !defined(MIJIN_CONTAINER_MEMORY_VIEW_HPP_INCLUDED)
+#define MIJIN_CONTAINER_MEMORY_VIEW_HPP_INCLUDED 1
+
+#include <bit>
+#include <cstddef>
+#include <span>
+#include "../debug/assert.hpp"
+#include "../util/traits.hpp"
+
+namespace mijin
+{
+
+//
+// public defines
+//
+
+//
+// public constants
+//
+
+//
+// public types
+//
+
+template<typename TBytes>
+class MemoryViewBase
+{
+public:
+    using size_type = std::size_t;
+private:
+    std::span<TBytes> bytes_;
+public:
+    MemoryViewBase() noexcept = default;
+    MemoryViewBase(const MemoryViewBase&) noexcept = default;
+    MemoryViewBase(copy_const_t<TBytes, void>* data, std::size_t size) noexcept : bytes_(static_cast<TBytes*>(data), size) {}
+
+    MemoryViewBase& operator=(const MemoryViewBase&) noexcept = default;
+    
+    [[nodiscard]] void* data() noexcept { return bytes_.data(); }
+    [[nodiscard]] const void* data() const noexcept { return bytes_.data(); }
+    [[nodiscard]] size_type byteSize() const noexcept { return bytes_.size(); }
+    [[nodiscard]] bool empty() const noexcept { return bytes_.empty(); }
+
+    template<typename T>
+    [[nodiscard]] std::span<T> makeSpan();
+
+    template<typename T>
+    [[nodiscard]] std::span<const T> makeSpan() const;
+};
+using MemoryView = MemoryViewBase<std::byte>;
+using ConstMemoryView = MemoryViewBase<const std::byte>;
+
+//
+// public functions
+//
+
+template<typename TBytes>
+template<typename T>
+std::span<T> MemoryViewBase<TBytes>::makeSpan()
+{
+    static_assert(!std::is_const_v<TBytes>, "Cannot create writable spans from const memory views.");
+    MIJIN_ASSERT(bytes_.size() % sizeof(T) == 0, "MemoryView cannot be divided into elements of this type.");
+    return {
+        std::bit_cast<T*>(bytes_.data()),
+        std::bit_cast<T*>(bytes_.data() + bytes_.size())
+    };
+}
+
+template<typename TBytes>
+template<typename T>
+std::span<const T> MemoryViewBase<TBytes>::makeSpan() const
+{
+    MIJIN_ASSERT(bytes_.size() % sizeof(T) == 0, "MemoryView cannot be divided into elements of this type.");
+    return {
+        std::bit_cast<const T*>(bytes_.data()),
+        std::bit_cast<const T*>(bytes_.data() + bytes_.size())
+    };
+}
+} // namespace mijin
+
+#endif // !defined(MIJIN_CONTAINER_MEMORY_VIEW_HPP_INCLUDED)