From 150ab70dc17eaa2469b8a852c2a1cc74e5a93e8f Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Sat, 5 Jun 2021 13:41:11 +0100
Subject: [PATCH] span has dedicated simple memory Slice child

---
 include/cow.hpp   |  4 ++--
 include/slice.hpp | 38 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/include/cow.hpp b/include/cow.hpp
index ab1364e..26758aa 100644
--- a/include/cow.hpp
+++ b/include/cow.hpp
@@ -6,7 +6,7 @@
 
 #include "slice.hpp"
 
-struct Cow : public Slice<unsigned char> {
+struct Cow : public Span<unsigned char> {
 	struct Fake;
 	Cow() = delete;
 
@@ -30,7 +30,7 @@ struct Cow : public Slice<unsigned char> {
 	/// 	  There is also likely no benefit using this over `size()` in LTO enabled builds.
 	///
 	/// XXX: Deprecated function for now. It seems `size()` offers better codegen on LTO and non-LTO enabled builds.
-	[[deprecated]] inline size_t size_unsafe() const { return _cow_size_unsafe(get_raw()); }
+	[[deprecated("size() is safer and offers better codegen.")]] inline size_t size_unsafe() const { return _cow_size_unsafe(get_raw()); }
 	
 	static Cow from_raw(cow_t* owned);
 
diff --git a/include/slice.hpp b/include/slice.hpp
index 29f343e..c5b63fa 100644
--- a/include/slice.hpp
+++ b/include/slice.hpp
@@ -1,7 +1,8 @@
 #pragma once
 
+/// A type that spans a sized region of memory
 template<typename T>
-struct Slice {
+struct Span {
 	virtual const void* area() const =0;
 	virtual void* area() = 0;
 	virtual size_t size() const = 0;
@@ -30,4 +31,39 @@ struct Slice {
 
 	template<typename U>
 	size_t size_as() const requires(sizeof(T) % sizeof(U) == 0) { return size_bytes() / sizeof(U); }
+
+	struct Slice;
+
+	inline bool bounds_ok(size_t start, size_t len)
+	{
+		return (start + len) < size();
+	}
+	inline bool bounds_ok(size_t start)
+	{
+		return start < size();
+	}
+
+	inline Slice slice(size_t start, size_t len) { if(bounds_ok(start,len)) return Slice(ptr()+start, len); else throw "Out of bounds slice"; }
+	inline Slice slice(size_t start) { return slice(start, size()-start); }
 };
+
+/// A slice of memory with a backing pointer and size.
+template<typename T>
+struct Span<T>::Slice : public Span<T> {
+	inline Slice(T* ptr, size_t sz) : _area((void*)ptr), _size(sz){}
+	inline Slice(const Span<T>& slice) : _area(slice.area()), _size(slice.size()){}
+	inline Slice(const Slice& copy) = default;
+	inline Slice(Slice&& copy) : _area(copy._area), _size(copy._size){ *const_cast<size_t*>(&copy._size) = 0; }
+	Slice() = delete;
+
+	inline const void* area() const override { return _area; }
+	inline void* area() override { return _area; }
+	inline size_t size() const override { return _size; }
+	
+	private:
+	void* const _area;
+	const size_t _size;
+};
+
+template<typename T>
+typename Span<T>::Slice Slice;