From 9c45e9c7df1efa5bc1c8e73b6eaef4726b828d3e Mon Sep 17 00:00:00 2001
From: Hannes Schulze <haschu0103@outlook.de>
Date: Tue, 4 Feb 2025 19:59:47 +0100
Subject: add span type

---
 lib/nes/common/span.hh | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 lib/nes/common/span.hh

(limited to 'lib/nes/common/span.hh')

diff --git a/lib/nes/common/span.hh b/lib/nes/common/span.hh
new file mode 100644
index 0000000..16eb129
--- /dev/null
+++ b/lib/nes/common/span.hh
@@ -0,0 +1,82 @@
+#pragma once
+
+#include "nes/common/types.hh"
+
+namespace nes
+{
+	namespace detail
+	{
+		struct span_unchecked{};
+
+		inline constexpr auto span_dynamic_length = u32{ 0xFFFF };
+
+		template<typename T>
+		struct remove_const
+		{
+			using type = T;
+		};
+
+		template<typename T>
+		struct remove_const<T const>
+		{
+			using type = T;
+		};
+	} // namespace detail
+
+	/// Implementation of a container similar to std::span in C++20.
+	template<typename T, u32 Length = detail::span_dynamic_length>
+	class span
+	{
+		template<typename U, u32 OtherLength>
+		friend class span;
+
+		T* data_{ nullptr };
+		u32 length_{ 0 };
+
+	public:
+		using iterator = T*;
+
+		explicit span()
+		{
+			static_assert(Length == 0 || Length == detail::span_dynamic_length);
+		}
+
+		explicit span(T* data, u32 const length)
+			: span{ data, length, {} }
+		{
+			static_assert(Length == detail::span_dynamic_length);
+		}
+
+		template<u32 ActualLength>
+		span(T (&data)[ActualLength])
+			: span{ data, ActualLength, {} }
+		{
+			static_assert(Length == ActualLength || Length == detail::span_dynamic_length);
+		}
+
+		span(span<typename detail::remove_const<T>::type, Length> const other)
+			: span{ other.data_, other.length_, {} }
+		{
+		}
+
+		auto get_data() const -> T* { return data_; }
+		auto get_length() const -> u32 { return length_; }
+
+		auto begin() const -> iterator { return data_; }
+		auto end() const -> iterator { return data_ + length_; }
+
+		auto subspan(u32 const first, u32 const length) const -> span<T> { return span{ data_ + first, length }; }
+		auto subspan(u32 const first) const -> span<T> { return subspan(length_ - first); }
+		template<u32 OtherLength>
+		auto subspan(u32 const first) const -> span<T, OtherLength> { return span<T, OtherLength>{ data_ + first, OtherLength, {} }; }
+
+		auto operator[](u32 const index) const -> T& { return data_[index]; }
+
+	private:
+		explicit span(T* data, u32 const length, detail::span_unchecked)
+			: data_{ data }
+			, length_{ length }
+		{
+		}
+	};
+} // namespace nes
\ No newline at end of file
-- 
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