cast.hpp helper

I was tired of manually bounds-checking my integer casts.

include/helpers/cast.hpp

@@ -0,0 +1,48 @@
+#pragma once
+
+#include <limits>
+#include <utility>
+#include <span>
+
+/**
+ * Helper functions for performing casts.
+ */
+namespace dusk::helpers::cast {
+    /**
+     * Implementation details of dusk::helpers::cast.
+     */
+    namespace _impl {
+        [[noreturn]] void overrun_high();
+        [[noreturn]] void overrun_low();
+    }
+
+    template <typename T>
+    concept IntCastable = std::is_integral_v<T> && std::is_trivially_copyable_v<T>;
+
+    /**
+     * Helper type that allows easily casting between integer types,
+     * that safely aborts if an overflow were to occur.
+     * Usage:
+     * @code
+     * size_t foobar = 20;
+     * int real = bounded_cast(foobar);
+     * @endcode
+     */
+    template <IntCastable Source>
+    struct bounded_cast {
+        Source src;
+
+        template <IntCastable Target>
+        [[nodiscard]] constexpr operator Target() const {
+            if (std::cmp_greater(src, std::numeric_limits<Target>::max())) [[unlikely]] {
+                _impl::overrun_high();
+            }
+
+            if (std::cmp_less(src, std::numeric_limits<Target>::min())) [[unlikely]] {
+                _impl::overrun_low();
+            }
+
+            return static_cast<Target>(src);
+        }
+    };
+}