dusklight/include/helpers/cast.hpp

#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);
        }
    };
}