From 854752ec0dc10277fa59531a3f3849817ddda0a0 Mon Sep 17 00:00:00 2001
From: ChUrl <christoph.urlacher@protonmail.com>
Date: Sun, 24 Jul 2022 21:49:38 +0200
Subject: [PATCH] primitive span implementation

---
 c_os/user/lib/Span.h | 61 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 c_os/user/lib/Span.h

diff --git a/c_os/user/lib/Span.h b/c_os/user/lib/Span.h
new file mode 100644
index 0000000..33ef319
--- /dev/null
+++ b/c_os/user/lib/Span.h
@@ -0,0 +1,61 @@
+#ifndef SPAN_INCLUDE_H
+#define SPAN_INCLUDE_H
+
+#include "user/lib/Iterator.h"
+#include <utility>
+
+namespace bse {
+
+    // 0 is unchecked
+    template<typename T, const std::size_t N = 0>
+    class span {
+    public:
+        using iterator = ContinuousIterator<T>;
+
+    private:
+        const T* ptr;
+        std::size_t sz = N;
+
+    public:
+        span() = default;
+
+        span(const T* first) : ptr(first) {}
+
+        span(const T* first, const T* last) : ptr(first), sz(last - first) {}
+
+        iterator begin() { return iterator(&ptr[0]); }
+        iterator begin() const { return iterator(&ptr[0]); }
+        // If size is unchecked end() is equal to begin()
+        iterator end() { return iterator(&ptr[N]); }
+        iterator end() const { return iterator(&ptr[N]); }
+
+        constexpr T& operator[](std::size_t i) {
+            if constexpr (N != 0 && i >= N) {
+                return nullptr;
+            }
+            return ptr[i];
+        }
+
+        constexpr const T& operator[](std::size_t i) const {
+            if constexpr (N != 0 && i >= N) {
+                return nullptr;
+            }
+            return ptr[i];
+        }
+
+        T* data() { return &ptr[0]; }
+        const T* data() const { return &ptr[0]; }
+
+        // First is inclusive, last exclusive [first, last)
+        span& subspan(std::size_t first, std::size_t last = N) {
+            return span(ptr + first, ptr + last - 1);
+        }
+
+        std::size_t size() const {
+            return sz;
+        }
+    };
+
+}  // namespace bse
+
+#endif