1 + 
//
 
2 + 
// Copyright (c) 2026 Michael Vandeberg
 
3 + 
//
 
4 + 
// Distributed under the Boost Software License, Version 1.0. (See accompanying
 
5 + 
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
6 + 
//
 
7 + 
// Official repository: https://github.com/cppalliance/capy
 
8 + 
//
 
9 +
 
10 + 
#ifndef BOOST_CAPY_DETAIL_SERVICE_SLOT_HPP
 
11 + 
#define BOOST_CAPY_DETAIL_SERVICE_SLOT_HPP
 
12 +
 
13 + 
#include <atomic>
 
14 + 
#include <cstddef>
 
15 +
 
16 + 
namespace boost {
 
17 + 
namespace capy {
 
18 + 
namespace detail {
 
19 +
 
20 + 
/* Slot ID infrastructure for O(1) service lookup.
 
21 +
 
22 + 
   Each distinct service type T gets a unique integer index via
 
23 + 
   service_slot<T>(). The index is assigned on first call from a
 
24 + 
   global atomic counter and cached in a function-local static.
 
25 + 
   Cross-DLL safety relies on COMDAT deduplication (same mechanism
 
26 + 
   as type_id_impl<T>::tag).
 
27 + 
*/
 
28 +
 
29 + 
inline std::atomic<std::size_t> next_service_slot{0};
 
30 +
 
31 + 
template<class T>
 
32 + 
std::size_t
 
33 + 
service_slot() noexcept
 
34 + 
{
 
35 + 
    static const std::size_t id =
 
36 + 
        next_service_slot.fetch_add(1, std::memory_order_relaxed);
 
37 + 
    return id;
 
38 + 
}
 
39 +
 
40 + 
} // namespace detail
 
41 + 
} // namespace capy
 
42 + 
} // namespace boost
 
43 +
 
44 + 
#endif