add util::span

src/util/span.hpp

@@ -0,0 +1,42 @@
+#pragma once
+
+#include <stdexcept>
+
+namespace util {
+    template <typename T>
+    class span {
+    public:
+        constexpr span(const T* ptr, size_t length)
+         : ptr(ptr), length(length) {}
+
+        const T& operator[](size_t index) const {
+            return ptr[index];
+        }
+
+        const T& at(size_t index) const {
+            if (index >= length) {
+                throw std::out_of_range();
+            }
+            return ptr[index];
+        }
+
+        auto begin() const {
+            return ptr;
+        }
+
+        auto end() const {
+            return ptr + length;
+        }
+
+        const T* data() const {
+            return ptr;
+        }
+
+        size_t size() const {
+            return length;
+        }
+    private:
+        const T* ptr;
+        size_t length;
+    };
+}