narrow_size.hpp

/*
 * VecMem project, part of the ACTS project (R&D line)
 *
 * (c) 2026 CERN for the benefit of the ACTS project
 *
 * Mozilla Public License Version 2.0
 */
#pragma once
 
// VecMem include(s).
#include "vecmem/utils/types.hpp"
 
// System include(s).
#include <cassert>
#include <cstddef>
#include <limits>
#include <type_traits>
 
namespace vecmem::details {
 
template <typename SIZE_TYPE, typename INPUT_TYPE>
VECMEM_HOST constexpr SIZE_TYPE narrow_size(INPUT_TYPE size) {
 
    static_assert(
        std::is_integral_v<SIZE_TYPE> && std::is_unsigned_v<SIZE_TYPE>,
        "The device-side size type must be an unsigned integer type");
    static_assert(
        std::is_integral_v<INPUT_TYPE> && std::is_unsigned_v<INPUT_TYPE>,
        "Only unsigned sizes can be narrowed with this helper");
 
    assert(static_cast<std::size_t>(size) <=
           static_cast<std::size_t>(std::numeric_limits<SIZE_TYPE>::max()));
    return static_cast<SIZE_TYPE>(size);
}
 
}  // namespace vecmem::details