1   
//
1   
//
2   
// Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
2   
// Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3   
//
3   
//
4   
// Distributed under the Boost Software License, Version 1.0. (See accompanying
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)
5   
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6   
//
6   
//
7   
// Official repository: https://github.com/cppalliance/capy
7   
// Official repository: https://github.com/cppalliance/capy
8   
//
8   
//
9  
9  
10   
#ifndef BOOST_CAPY_EXECUTION_CONTEXT_HPP
10   
#ifndef BOOST_CAPY_EXECUTION_CONTEXT_HPP
11   
#define BOOST_CAPY_EXECUTION_CONTEXT_HPP
11   
#define BOOST_CAPY_EXECUTION_CONTEXT_HPP
12  
12  
13   
#include <boost/capy/detail/config.hpp>
13   
#include <boost/capy/detail/config.hpp>
14   
#include <boost/capy/detail/frame_memory_resource.hpp>
14   
#include <boost/capy/detail/frame_memory_resource.hpp>
 
15 + 
#include <boost/capy/detail/service_slot.hpp>
15   
#include <boost/capy/detail/type_id.hpp>
16   
#include <boost/capy/detail/type_id.hpp>
16   
#include <boost/capy/concept/executor.hpp>
17   
#include <boost/capy/concept/executor.hpp>
 
18 + 
#include <atomic>
17   
#include <concepts>
19   
#include <concepts>
18   
#include <memory>
20   
#include <memory>
19   
#include <memory_resource>
21   
#include <memory_resource>
20   
#include <mutex>
22   
#include <mutex>
21   
#include <tuple>
23   
#include <tuple>
22   
#include <type_traits>
24   
#include <type_traits>
23   
#include <utility>
25   
#include <utility>
24  
26  
25   
namespace boost {
27   
namespace boost {
26   
namespace capy {
28   
namespace capy {
27  
29  
28   
/** Base class for I/O object containers providing service management.
30   
/** Base class for I/O object containers providing service management.
29  
31  
30   
    An execution context represents a place where function objects are
32   
    An execution context represents a place where function objects are
31   
    executed. It provides a service registry where polymorphic services
33   
    executed. It provides a service registry where polymorphic services
32   
    can be stored and retrieved by type. Each service type may be stored
34   
    can be stored and retrieved by type. Each service type may be stored
33   
    at most once. Services may specify a nested `key_type` to enable
35   
    at most once. Services may specify a nested `key_type` to enable
34   
    lookup by a base class type.
36   
    lookup by a base class type.
35  
37  
36   
    Derived classes such as `io_context` extend this to provide
38   
    Derived classes such as `io_context` extend this to provide
37   
    execution facilities like event loops and thread pools. Derived
39   
    execution facilities like event loops and thread pools. Derived
38   
    class destructors must call `shutdown()` and `destroy()` to ensure
40   
    class destructors must call `shutdown()` and `destroy()` to ensure
39   
    proper service cleanup before member destruction.
41   
    proper service cleanup before member destruction.
40  
42  
41   
    @par Service Lifecycle
43   
    @par Service Lifecycle
42   
    Services are created on first use via `use_service()` or explicitly
44   
    Services are created on first use via `use_service()` or explicitly
43   
    via `make_service()`. During destruction, `shutdown()` is called on
45   
    via `make_service()`. During destruction, `shutdown()` is called on
44   
    each service in reverse order of creation, then `destroy()` deletes
46   
    each service in reverse order of creation, then `destroy()` deletes
45   
    them. Both functions are idempotent.
47   
    them. Both functions are idempotent.
46  
48  
47   
    @par Thread Safety
49   
    @par Thread Safety
48   
    Service registration and lookup functions are thread-safe.
50   
    Service registration and lookup functions are thread-safe.
49   
    The `shutdown()` and `destroy()` functions are not thread-safe
51   
    The `shutdown()` and `destroy()` functions are not thread-safe
50   
    and must only be called during destruction.
52   
    and must only be called during destruction.
51  
53  
52   
    @par Example
54   
    @par Example
53   
    @code
55   
    @code
54   
    struct file_service : execution_context::service
56   
    struct file_service : execution_context::service
55   
    {
57   
    {
56   
    protected:
58   
    protected:
57   
        void shutdown() override {}
59   
        void shutdown() override {}
58   
    };
60   
    };
59  
61  
60   
    struct posix_file_service : file_service
62   
    struct posix_file_service : file_service
61   
    {
63   
    {
62   
        using key_type = file_service;
64   
        using key_type = file_service;
63  
65  
64   
        explicit posix_file_service(execution_context&) {}
66   
        explicit posix_file_service(execution_context&) {}
65   
    };
67   
    };
66  
68  
67   
    class io_context : public execution_context
69   
    class io_context : public execution_context
68   
    {
70   
    {
69   
    public:
71   
    public:
70   
        ~io_context()
72   
        ~io_context()
71   
        {
73   
        {
72   
            shutdown();
74   
            shutdown();
73   
            destroy();
75   
            destroy();
74   
        }
76   
        }
75   
    };
77   
    };
76  
78  
77   
    io_context ctx;
79   
    io_context ctx;
78   
    ctx.make_service<posix_file_service>();
80   
    ctx.make_service<posix_file_service>();
79   
    ctx.find_service<file_service>();       // returns posix_file_service*
81   
    ctx.find_service<file_service>();       // returns posix_file_service*
80   
    ctx.find_service<posix_file_service>(); // also works
82   
    ctx.find_service<posix_file_service>(); // also works
81   
    @endcode
83   
    @endcode
82  
84  
83   
    @see service, is_execution_context
85   
    @see service, is_execution_context
84   
*/
86   
*/
85   
class BOOST_CAPY_DECL
87   
class BOOST_CAPY_DECL
86   
    execution_context
88   
    execution_context
87   
{
89   
{
88   
    detail::type_info const* ti_ = nullptr;
90   
    detail::type_info const* ti_ = nullptr;
89  
91  
90   
    template<class T, class = void>
92   
    template<class T, class = void>
91   
    struct get_key : std::false_type
93   
    struct get_key : std::false_type
92   
    {};
94   
    {};
93  
95  
94   
    template<class T>
96   
    template<class T>
95   
    struct get_key<T, std::void_t<typename T::key_type>> : std::true_type
97   
    struct get_key<T, std::void_t<typename T::key_type>> : std::true_type
96   
    {
98   
    {
97   
        using type = typename T::key_type;
99   
        using type = typename T::key_type;
98   
    };
100   
    };
99   
protected:
101   
protected:
100   
    template< typename Derived >
102   
    template< typename Derived >
101   
    explicit execution_context( Derived* ) noexcept;
103   
    explicit execution_context( Derived* ) noexcept;
102  
104  
103   
public:
105   
public:
104   
    //------------------------------------------------
106   
    //------------------------------------------------
105  
107  
106   
    /** Abstract base class for services owned by an execution context.
108   
    /** Abstract base class for services owned by an execution context.
107  
109  
108   
        Services provide extensible functionality to an execution context.
110   
        Services provide extensible functionality to an execution context.
109   
        Each service type can be registered at most once. Services are
111   
        Each service type can be registered at most once. Services are
110   
        created via `use_service()` or `make_service()` and are owned by
112   
        created via `use_service()` or `make_service()` and are owned by
111   
        the execution context for their lifetime.
113   
        the execution context for their lifetime.
112  
114  
113   
        Derived classes must implement the pure virtual `shutdown()` member
115   
        Derived classes must implement the pure virtual `shutdown()` member
114   
        function, which is called when the owning execution context is
116   
        function, which is called when the owning execution context is
115   
        being destroyed. The `shutdown()` function should release resources
117   
        being destroyed. The `shutdown()` function should release resources
116   
        and cancel outstanding operations without blocking.
118   
        and cancel outstanding operations without blocking.
117  
119  
118   
        @par Deriving from service
120   
        @par Deriving from service
119   
        @li Implement `shutdown()` to perform cleanup.
121   
        @li Implement `shutdown()` to perform cleanup.
120   
        @li Accept `execution_context&` as the first constructor parameter.
122   
        @li Accept `execution_context&` as the first constructor parameter.
121   
        @li Optionally define `key_type` to enable base-class lookup.
123   
        @li Optionally define `key_type` to enable base-class lookup.
122  
124  
123   
        @par Example
125   
        @par Example
124   
        @code
126   
        @code
125   
        struct my_service : execution_context::service
127   
        struct my_service : execution_context::service
126   
        {
128   
        {
127   
            explicit my_service(execution_context&) {}
129   
            explicit my_service(execution_context&) {}
128  
130  
129   
        protected:
131   
        protected:
130   
            void shutdown() override
132   
            void shutdown() override
131   
            {
133   
            {
132   
                // Cancel pending operations, release resources
134   
                // Cancel pending operations, release resources
133   
            }
135   
            }
134   
        };
136   
        };
135   
        @endcode
137   
        @endcode
136  
138  
137   
        @see execution_context
139   
        @see execution_context
138   
    */
140   
    */
139   
    class BOOST_CAPY_DECL
141   
    class BOOST_CAPY_DECL
140   
        service
142   
        service
141   
    {
143   
    {
142   
    public:
144   
    public:
143   
        virtual ~service() = default;
145   
        virtual ~service() = default;
144  
146  
145   
    protected:
147   
    protected:
146   
        service() = default;
148   
        service() = default;
147  
149  
148   
        /** Called when the owning execution context shuts down.
150   
        /** Called when the owning execution context shuts down.
149  
151  
150   
            Implementations should release resources and cancel any
152   
            Implementations should release resources and cancel any
151   
            outstanding asynchronous operations. This function must
153   
            outstanding asynchronous operations. This function must
152   
            not block and must not throw exceptions. Services are
154   
            not block and must not throw exceptions. Services are
153   
            shut down in reverse order of creation.
155   
            shut down in reverse order of creation.
154  
156  
155   
            @par Exception Safety
157   
            @par Exception Safety
156   
            No-throw guarantee.
158   
            No-throw guarantee.
157   
        */
159   
        */
158   
        virtual void shutdown() = 0;
160   
        virtual void shutdown() = 0;
159  
161  
160   
    private:
162   
    private:
161   
        friend class execution_context;
163   
        friend class execution_context;
162  
164  
163   
        service* next_ = nullptr;
165   
        service* next_ = nullptr;
164  
166  
165   
// warning C4251: 'std::type_index' needs to have dll-interface
167   
// warning C4251: 'std::type_index' needs to have dll-interface
166   
        BOOST_CAPY_MSVC_WARNING_PUSH
168   
        BOOST_CAPY_MSVC_WARNING_PUSH
167   
        BOOST_CAPY_MSVC_WARNING_DISABLE(4251)
169   
        BOOST_CAPY_MSVC_WARNING_DISABLE(4251)
168   
        detail::type_index t0_{detail::type_id<void>()};
170   
        detail::type_index t0_{detail::type_id<void>()};
169   
        detail::type_index t1_{detail::type_id<void>()};
171   
        detail::type_index t1_{detail::type_id<void>()};
170   
        BOOST_CAPY_MSVC_WARNING_POP
172   
        BOOST_CAPY_MSVC_WARNING_POP
171   
    };
173   
    };
172  
174  
173   
    //------------------------------------------------
175   
    //------------------------------------------------
174  
176  
175   
    execution_context(execution_context const&) = delete;
177   
    execution_context(execution_context const&) = delete;
176  
178  
177   
    execution_context& operator=(execution_context const&) = delete;
179   
    execution_context& operator=(execution_context const&) = delete;
178  
180  
179   
    /** Destructor.
181   
    /** Destructor.
180  
182  
181   
        Calls `shutdown()` then `destroy()` to clean up all services.
183   
        Calls `shutdown()` then `destroy()` to clean up all services.
182  
184  
183   
        @par Effects
185   
        @par Effects
184   
        All services are shut down and deleted in reverse order
186   
        All services are shut down and deleted in reverse order
185   
        of creation.
187   
        of creation.
186  
188  
187   
        @par Exception Safety
189   
        @par Exception Safety
188   
        No-throw guarantee.
190   
        No-throw guarantee.
189   
    */
191   
    */
190   
    ~execution_context();
192   
    ~execution_context();
191  
193  
192   
    /** Construct a default instance.
194   
    /** Construct a default instance.
193  
195  
194   
        @par Exception Safety
196   
        @par Exception Safety
195   
        Strong guarantee.
197   
        Strong guarantee.
196   
    */
198   
    */
197   
    execution_context();
199   
    execution_context();
198  
200  
199   
    /** Return true if a service of type T exists.
201   
    /** Return true if a service of type T exists.
200  
202  
201   
        @par Thread Safety
203   
        @par Thread Safety
202   
        Thread-safe.
204   
        Thread-safe.
203  
205  
204   
        @tparam T The type of service to check.
206   
        @tparam T The type of service to check.
205  
207  
206   
        @return `true` if the service exists.
208   
        @return `true` if the service exists.
207   
    */
209   
    */
208   
    template<class T>
210   
    template<class T>
209   
    bool has_service() const noexcept
211   
    bool has_service() const noexcept
210   
    {
212   
    {
211   
        return find_service<T>() != nullptr;
213   
        return find_service<T>() != nullptr;
212   
    }
214   
    }
213  
215  
214   
    /** Return a pointer to the service of type T, or nullptr.
216   
    /** Return a pointer to the service of type T, or nullptr.
215  
217  
216   
        @par Thread Safety
218   
        @par Thread Safety
217   
        Thread-safe.
219   
        Thread-safe.
218  
220  
219   
        @tparam T The type of service to find.
221   
        @tparam T The type of service to find.
220  
222  
221   
        @return A pointer to the service, or `nullptr` if not present.
223   
        @return A pointer to the service, or `nullptr` if not present.
222   
    */
224   
    */
223   
    template<class T>
225   
    template<class T>
224   
    T* find_service() const noexcept
226   
    T* find_service() const noexcept
225   
    {
227   
    {
 
228 + 
        auto id = detail::service_slot<T>();
 
229 + 
        if(id < max_service_slots)
 
230 + 
        {
 
231 + 
            auto* p = slots_[id].load(
 
232 + 
                std::memory_order_acquire);
 
233 + 
            if(p)
 
234 + 
                return static_cast<T*>(p);
 
235 + 
        }
226   
        std::lock_guard<std::mutex> lock(mutex_);
236   
        std::lock_guard<std::mutex> lock(mutex_);
227   
        return static_cast<T*>(find_impl(detail::type_id<T>()));
237   
        return static_cast<T*>(find_impl(detail::type_id<T>()));
228   
    }
238   
    }
229  
239  
230   
    /** Return a reference to the service of type T, creating it if needed.
240   
    /** Return a reference to the service of type T, creating it if needed.
231  
241  
232   
        If no service of type T exists, one is created by calling
242   
        If no service of type T exists, one is created by calling
233   
        `T(execution_context&)`. If T has a nested `key_type`, the
243   
        `T(execution_context&)`. If T has a nested `key_type`, the
234   
        service is also indexed under that type.
244   
        service is also indexed under that type.
235  
245  
236   
        @par Constraints
246   
        @par Constraints
237   
        @li `T` must derive from `service`.
247   
        @li `T` must derive from `service`.
238   
        @li `T` must be constructible from `execution_context&`.
248   
        @li `T` must be constructible from `execution_context&`.
239  
249  
240   
        @par Exception Safety
250   
        @par Exception Safety
241   
        Strong guarantee. If service creation throws, the container
251   
        Strong guarantee. If service creation throws, the container
242   
        is unchanged.
252   
        is unchanged.
243  
253  
244   
        @par Thread Safety
254   
        @par Thread Safety
245   
        Thread-safe.
255   
        Thread-safe.
246  
256  
247   
        @tparam T The type of service to retrieve or create.
257   
        @tparam T The type of service to retrieve or create.
248  
258  
249   
        @return A reference to the service.
259   
        @return A reference to the service.
250   
    */
260   
    */
251   
    template<class T>
261   
    template<class T>
252   
    T& use_service()
262   
    T& use_service()
253   
    {
263   
    {
254   
        static_assert(std::is_base_of<service, T>::value,
264   
        static_assert(std::is_base_of<service, T>::value,
255   
            "T must derive from service");
265   
            "T must derive from service");
256   
        static_assert(std::is_constructible<T, execution_context&>::value,
266   
        static_assert(std::is_constructible<T, execution_context&>::value,
257   
            "T must be constructible from execution_context&");
267   
            "T must be constructible from execution_context&");
 
268 + 
        if constexpr(get_key<T>::value)
 
269 + 
        {
 
270 + 
            static_assert(
 
271 + 
                std::is_convertible<T&, typename get_key<T>::type&>::value,
 
272 + 
                "T& must be convertible to key_type&");
 
273 + 
        }
 
274 +
 
275 + 
        // Fast path: O(1) slot lookup
 
276 + 
        {
 
277 + 
            auto id = detail::service_slot<T>();
 
278 + 
            if(id < max_service_slots)
 
279 + 
            {
 
280 + 
                auto* p = slots_[id].load(
 
281 + 
                    std::memory_order_acquire);
 
282 + 
                if(p)
 
283 + 
                    return static_cast<T&>(*p);
 
284 + 
            }
 
285 + 
        }
258  
286  
259   
        struct impl : factory
287   
        struct impl : factory
260   
        {
288   
        {
261   
            impl()
289   
            impl()
262   
                : factory(
290   
                : factory(
263   
                    detail::type_id<T>(),
291   
                    detail::type_id<T>(),
264   
                    get_key<T>::value
292   
                    get_key<T>::value
265   
                        ? detail::type_id<typename get_key<T>::type>()
293   
                        ? detail::type_id<typename get_key<T>::type>()
266 - 
                        : detail::type_id<T>())
294 + 
                        : detail::type_id<T>(),
 
295 + 
                    detail::service_slot<T>(),
 
296 + 
                    get_key<T>::value
 
297 + 
                        ? detail::service_slot<typename get_key<T>::type>()
 
298 + 
                        : detail::service_slot<T>())
267   
            {
299   
            {
268   
            }
300   
            }
269  
301  
270   
            service* create(execution_context& ctx) override
302   
            service* create(execution_context& ctx) override
271   
            {
303   
            {
272   
                return new T(ctx);
304   
                return new T(ctx);
273   
            }
305   
            }
274   
        };
306   
        };
275  
307  
276   
        impl f;
308   
        impl f;
277   
        return static_cast<T&>(use_service_impl(f));
309   
        return static_cast<T&>(use_service_impl(f));
278   
    }
310   
    }
279  
311  
280   
    /** Construct and add a service.
312   
    /** Construct and add a service.
281  
313  
282   
        A new service of type T is constructed using the provided
314   
        A new service of type T is constructed using the provided
283   
        arguments and added to the container. If T has a nested
315   
        arguments and added to the container. If T has a nested
284   
        `key_type`, the service is also indexed under that type.
316   
        `key_type`, the service is also indexed under that type.
285  
317  
286   
        @par Constraints
318   
        @par Constraints
287   
        @li `T` must derive from `service`.
319   
        @li `T` must derive from `service`.
288   
        @li `T` must be constructible from `execution_context&, Args...`.
320   
        @li `T` must be constructible from `execution_context&, Args...`.
289   
        @li If `T::key_type` exists, `T&` must be convertible to `key_type&`.
321   
        @li If `T::key_type` exists, `T&` must be convertible to `key_type&`.
290  
322  
291   
        @par Exception Safety
323   
        @par Exception Safety
292   
        Strong guarantee. If service creation throws, the container
324   
        Strong guarantee. If service creation throws, the container
293   
        is unchanged.
325   
        is unchanged.
294  
326  
295   
        @par Thread Safety
327   
        @par Thread Safety
296   
        Thread-safe.
328   
        Thread-safe.
297  
329  
298   
        @throws std::invalid_argument if a service of the same type
330   
        @throws std::invalid_argument if a service of the same type
299   
            or `key_type` already exists.
331   
            or `key_type` already exists.
300  
332  
301   
        @tparam T The type of service to create.
333   
        @tparam T The type of service to create.
302  
334  
303   
        @param args Arguments forwarded to the constructor of T.
335   
        @param args Arguments forwarded to the constructor of T.
304  
336  
305   
        @return A reference to the created service.
337   
        @return A reference to the created service.
306   
    */
338   
    */
307   
    template<class T, class... Args>
339   
    template<class T, class... Args>
308   
    T& make_service(Args&&... args)
340   
    T& make_service(Args&&... args)
309   
    {
341   
    {
310   
        static_assert(std::is_base_of<service, T>::value,
342   
        static_assert(std::is_base_of<service, T>::value,
311   
            "T must derive from service");
343   
            "T must derive from service");
312   
        if constexpr(get_key<T>::value)
344   
        if constexpr(get_key<T>::value)
313   
        {
345   
        {
314   
            static_assert(
346   
            static_assert(
315   
                std::is_convertible<T&, typename get_key<T>::type&>::value,
347   
                std::is_convertible<T&, typename get_key<T>::type&>::value,
316   
                "T& must be convertible to key_type&");
348   
                "T& must be convertible to key_type&");
317   
        }
349   
        }
318  
350  
319   
        struct impl : factory
351   
        struct impl : factory
320   
        {
352   
        {
321   
            std::tuple<Args&&...> args_;
353   
            std::tuple<Args&&...> args_;
322  
354  
323   
            explicit impl(Args&&... a)
355   
            explicit impl(Args&&... a)
324   
                : factory(
356   
                : factory(
325   
                    detail::type_id<T>(),
357   
                    detail::type_id<T>(),
326   
                    get_key<T>::value
358   
                    get_key<T>::value
327   
                        ? detail::type_id<typename get_key<T>::type>()
359   
                        ? detail::type_id<typename get_key<T>::type>()
328 - 
                        : detail::type_id<T>())
360 + 
                        : detail::type_id<T>(),
 
361 + 
                    detail::service_slot<T>(),
 
362 + 
                    get_key<T>::value
 
363 + 
                        ? detail::service_slot<typename get_key<T>::type>()
 
364 + 
                        : detail::service_slot<T>())
329   
                , args_(std::forward<Args>(a)...)
365   
                , args_(std::forward<Args>(a)...)
330   
            {
366   
            {
331   
            }
367   
            }
332  
368  
333   
            service* create(execution_context& ctx) override
369   
            service* create(execution_context& ctx) override
334   
            {
370   
            {
335   
                return std::apply([&ctx](auto&&... a) {
371   
                return std::apply([&ctx](auto&&... a) {
336   
                    return new T(ctx, std::forward<decltype(a)>(a)...);
372   
                    return new T(ctx, std::forward<decltype(a)>(a)...);
337   
                }, std::move(args_));
373   
                }, std::move(args_));
338   
            }
374   
            }
339   
        };
375   
        };
340  
376  
341   
        impl f(std::forward<Args>(args)...);
377   
        impl f(std::forward<Args>(args)...);
342   
        return static_cast<T&>(make_service_impl(f));
378   
        return static_cast<T&>(make_service_impl(f));
343   
    }
379   
    }
344  
380  
345   
    //------------------------------------------------
381   
    //------------------------------------------------
346  
382  
347   
    /** Return the memory resource used for coroutine frame allocation.
383   
    /** Return the memory resource used for coroutine frame allocation.
348  
384  
349   
        The returned pointer is valid for the lifetime of this context.
385   
        The returned pointer is valid for the lifetime of this context.
350   
        By default, this returns a pointer to the recycling memory
386   
        By default, this returns a pointer to the recycling memory
351   
        resource which pools frame allocations for reuse.
387   
        resource which pools frame allocations for reuse.
352  
388  
353   
        @return Pointer to the frame allocator.
389   
        @return Pointer to the frame allocator.
354  
390  
355   
        @see set_frame_allocator
391   
        @see set_frame_allocator
356   
    */
392   
    */
357   
    std::pmr::memory_resource*
393   
    std::pmr::memory_resource*
358   
    get_frame_allocator() const noexcept
394   
    get_frame_allocator() const noexcept
359   
    {
395   
    {
360   
        return frame_alloc_;
396   
        return frame_alloc_;
361   
    }
397   
    }
362  
398  
363   
    /** Set the memory resource used for coroutine frame allocation.
399   
    /** Set the memory resource used for coroutine frame allocation.
364  
400  
365   
        The caller is responsible for ensuring the memory resource
401   
        The caller is responsible for ensuring the memory resource
366   
        remains valid for the lifetime of all coroutines launched
402   
        remains valid for the lifetime of all coroutines launched
367   
        using this context's executor.
403   
        using this context's executor.
368  
404  
369   
        @par Thread Safety
405   
        @par Thread Safety
370   
        Not thread-safe. Must not be called while any thread may
406   
        Not thread-safe. Must not be called while any thread may
371   
        be referencing this execution context or its executor.
407   
        be referencing this execution context or its executor.
372  
408  
373   
        @param mr Pointer to the memory resource.
409   
        @param mr Pointer to the memory resource.
374  
410  
375   
        @see get_frame_allocator
411   
        @see get_frame_allocator
376   
    */
412   
    */
377   
    void
413   
    void
378   
    set_frame_allocator(std::pmr::memory_resource* mr) noexcept
414   
    set_frame_allocator(std::pmr::memory_resource* mr) noexcept
379   
    {
415   
    {
380   
        owned_.reset();
416   
        owned_.reset();
381   
        frame_alloc_ = mr;
417   
        frame_alloc_ = mr;
382   
    }
418   
    }
383  
419  
384   
    /** Set the frame allocator from a standard Allocator.
420   
    /** Set the frame allocator from a standard Allocator.
385  
421  
386   
        The allocator is wrapped in an internal memory resource
422   
        The allocator is wrapped in an internal memory resource
387   
        adapter owned by this context. The wrapper remains valid
423   
        adapter owned by this context. The wrapper remains valid
388   
        for the lifetime of this context or until a subsequent
424   
        for the lifetime of this context or until a subsequent
389   
        call to set_frame_allocator.
425   
        call to set_frame_allocator.
390  
426  
391   
        @par Thread Safety
427   
        @par Thread Safety
392   
        Not thread-safe. Must not be called while any thread may
428   
        Not thread-safe. Must not be called while any thread may
393   
        be referencing this execution context or its executor.
429   
        be referencing this execution context or its executor.
394  
430  
395   
        @tparam Allocator The allocator type satisfying the
431   
        @tparam Allocator The allocator type satisfying the
396   
            standard Allocator requirements.
432   
            standard Allocator requirements.
397  
433  
398   
        @param a The allocator to use.
434   
        @param a The allocator to use.
399  
435  
400   
        @see get_frame_allocator
436   
        @see get_frame_allocator
401   
    */
437   
    */
402   
    template<class Allocator>
438   
    template<class Allocator>
403   
        requires (!std::is_pointer_v<Allocator>)
439   
        requires (!std::is_pointer_v<Allocator>)
404   
    void
440   
    void
405   
    set_frame_allocator(Allocator const& a)
441   
    set_frame_allocator(Allocator const& a)
406   
    {
442   
    {
407   
        static_assert(
443   
        static_assert(
408   
            requires { typename std::allocator_traits<Allocator>::value_type; },
444   
            requires { typename std::allocator_traits<Allocator>::value_type; },
409   
            "Allocator must satisfy allocator requirements");
445   
            "Allocator must satisfy allocator requirements");
410   
        static_assert(
446   
        static_assert(
411   
            std::is_copy_constructible_v<Allocator>,
447   
            std::is_copy_constructible_v<Allocator>,
412   
            "Allocator must be copy constructible");
448   
            "Allocator must be copy constructible");
413  
449  
414   
        auto p = std::make_shared<
450   
        auto p = std::make_shared<
415   
            detail::frame_memory_resource<Allocator>>(a);
451   
            detail::frame_memory_resource<Allocator>>(a);
416   
        frame_alloc_ = p.get();
452   
        frame_alloc_ = p.get();
417   
        owned_ = std::move(p);
453   
        owned_ = std::move(p);
418   
    }
454   
    }
419  
455  
420   
    /** Return a pointer to this context if it matches the
456   
    /** Return a pointer to this context if it matches the
421   
        requested type.
457   
        requested type.
422  
458  
423   
        Performs a type check and downcasts `this` when the
459   
        Performs a type check and downcasts `this` when the
424   
        types match, or returns `nullptr` otherwise. Analogous
460   
        types match, or returns `nullptr` otherwise. Analogous
425   
        to `std::any_cast< ExecutionContext >( &a )`.
461   
        to `std::any_cast< ExecutionContext >( &a )`.
426  
462  
427   
        @tparam ExecutionContext The derived context type to
463   
        @tparam ExecutionContext The derived context type to
428   
            retrieve.
464   
            retrieve.
429  
465  
430   
        @return A pointer to this context as the requested
466   
        @return A pointer to this context as the requested
431   
            type, or `nullptr` if the type does not match.
467   
            type, or `nullptr` if the type does not match.
432   
    */
468   
    */
433   
    template< typename ExecutionContext >
469   
    template< typename ExecutionContext >
434   
    const ExecutionContext* target() const
470   
    const ExecutionContext* target() const
435   
    {
471   
    {
436   
        if ( ti_ && *ti_ == detail::type_id< ExecutionContext >() )
472   
        if ( ti_ && *ti_ == detail::type_id< ExecutionContext >() )
437   
           return static_cast< ExecutionContext const* >( this );
473   
           return static_cast< ExecutionContext const* >( this );
438   
        return nullptr;
474   
        return nullptr;
439   
    }
475   
    }
440  
476  
441   
    /// @copydoc target() const
477   
    /// @copydoc target() const
442   
    template< typename ExecutionContext >
478   
    template< typename ExecutionContext >
443   
    ExecutionContext* target()
479   
    ExecutionContext* target()
444   
    {
480   
    {
445   
        if ( ti_ && *ti_ == detail::type_id< ExecutionContext >() )
481   
        if ( ti_ && *ti_ == detail::type_id< ExecutionContext >() )
446   
           return static_cast< ExecutionContext* >( this );
482   
           return static_cast< ExecutionContext* >( this );
447   
        return nullptr;
483   
        return nullptr;
448   
    }
484   
    }
449  
485  
450   
protected:
486   
protected:
451   
    /** Shut down all services.
487   
    /** Shut down all services.
452  
488  
453   
        Calls `shutdown()` on each service in reverse order of creation.
489   
        Calls `shutdown()` on each service in reverse order of creation.
454   
        After this call, services remain allocated but are in a stopped
490   
        After this call, services remain allocated but are in a stopped
455   
        state. Derived classes should call this in their destructor
491   
        state. Derived classes should call this in their destructor
456   
        before any members are destroyed. This function is idempotent;
492   
        before any members are destroyed. This function is idempotent;
457   
        subsequent calls have no effect.
493   
        subsequent calls have no effect.
458  
494  
459   
        @par Effects
495   
        @par Effects
460   
        Each service's `shutdown()` member function is invoked once.
496   
        Each service's `shutdown()` member function is invoked once.
461  
497  
462   
        @par Postconditions
498   
        @par Postconditions
463   
        @li All services are in a stopped state.
499   
        @li All services are in a stopped state.
464  
500  
465   
        @par Exception Safety
501   
        @par Exception Safety
466   
        No-throw guarantee.
502   
        No-throw guarantee.
467  
503  
468   
        @par Thread Safety
504   
        @par Thread Safety
469   
        Not thread-safe. Must not be called concurrently with other
505   
        Not thread-safe. Must not be called concurrently with other
470   
        operations on this execution_context.
506   
        operations on this execution_context.
471   
    */
507   
    */
472   
    void shutdown() noexcept;
508   
    void shutdown() noexcept;
473  
509  
474   
    /** Destroy all services.
510   
    /** Destroy all services.
475  
511  
476   
        Deletes all services in reverse order of creation. Derived
512   
        Deletes all services in reverse order of creation. Derived
477   
        classes should call this as the final step of destruction.
513   
        classes should call this as the final step of destruction.
478   
        This function is idempotent; subsequent calls have no effect.
514   
        This function is idempotent; subsequent calls have no effect.
479  
515  
480   
        @par Preconditions
516   
        @par Preconditions
481   
        @li `shutdown()` has been called.
517   
        @li `shutdown()` has been called.
482  
518  
483   
        @par Effects
519   
        @par Effects
484   
        All services are deleted and removed from the container.
520   
        All services are deleted and removed from the container.
485  
521  
486   
        @par Postconditions
522   
        @par Postconditions
487   
        @li The service container is empty.
523   
        @li The service container is empty.
488  
524  
489   
        @par Exception Safety
525   
        @par Exception Safety
490   
        No-throw guarantee.
526   
        No-throw guarantee.
491  
527  
492   
        @par Thread Safety
528   
        @par Thread Safety
493   
        Not thread-safe. Must not be called concurrently with other
529   
        Not thread-safe. Must not be called concurrently with other
494   
        operations on this execution_context.
530   
        operations on this execution_context.
495   
    */
531   
    */
496   
    void destroy() noexcept;
532   
    void destroy() noexcept;
497  
533  
498   
private:
534   
private:
499   
    struct BOOST_CAPY_DECL
535   
    struct BOOST_CAPY_DECL
500   
        factory
536   
        factory
501   
    {
537   
    {
502   
// warning C4251: 'std::type_index' needs to have dll-interface
538   
// warning C4251: 'std::type_index' needs to have dll-interface
503   
        BOOST_CAPY_MSVC_WARNING_PUSH
539   
        BOOST_CAPY_MSVC_WARNING_PUSH
504   
        BOOST_CAPY_MSVC_WARNING_DISABLE(4251)
540   
        BOOST_CAPY_MSVC_WARNING_DISABLE(4251)
505   
        detail::type_index t0;
541   
        detail::type_index t0;
506   
        detail::type_index t1;
542   
        detail::type_index t1;
507   
        BOOST_CAPY_MSVC_WARNING_POP
543   
        BOOST_CAPY_MSVC_WARNING_POP
 
544 + 
        std::size_t slot0;
 
545 + 
        std::size_t slot1;
508  
546  
509   
        factory(
547   
        factory(
510   
            detail::type_info const& t0_,
548   
            detail::type_info const& t0_,
511 - 
            detail::type_info const& t1_)
549 + 
            detail::type_info const& t1_,
 
550 + 
            std::size_t s0,
 
551 + 
            std::size_t s1)
512   
            : t0(t0_), t1(t1_)
552   
            : t0(t0_), t1(t1_)
 
553 + 
            , slot0(s0), slot1(s1)
513   
        {
554   
        {
514   
        }
555   
        }
515  
556  
516   
        virtual service* create(execution_context&) = 0;
557   
        virtual service* create(execution_context&) = 0;
517  
558  
518   
    protected:
559   
    protected:
519   
        ~factory() = default;
560   
        ~factory() = default;
520   
    };
561   
    };
521  
562  
522   
    service* find_impl(detail::type_index ti) const noexcept;
563   
    service* find_impl(detail::type_index ti) const noexcept;
523   
    service& use_service_impl(factory& f);
564   
    service& use_service_impl(factory& f);
524   
    service& make_service_impl(factory& f);
565   
    service& make_service_impl(factory& f);
525  
566  
526 - 
// warning C4251: std::mutex, std::shared_ptr need dll-interface
567 + 
// warning C4251: std::mutex, std::shared_ptr, std::atomic need dll-interface
527   
    BOOST_CAPY_MSVC_WARNING_PUSH
568   
    BOOST_CAPY_MSVC_WARNING_PUSH
528   
    BOOST_CAPY_MSVC_WARNING_DISABLE(4251)
569   
    BOOST_CAPY_MSVC_WARNING_DISABLE(4251)
529   
    mutable std::mutex mutex_;
570   
    mutable std::mutex mutex_;
530   
    std::shared_ptr<void> owned_;
571   
    std::shared_ptr<void> owned_;
531   
    BOOST_CAPY_MSVC_WARNING_POP
572   
    BOOST_CAPY_MSVC_WARNING_POP
532   
    std::pmr::memory_resource* frame_alloc_ = nullptr;
573   
    std::pmr::memory_resource* frame_alloc_ = nullptr;
533   
    service* head_ = nullptr;
574   
    service* head_ = nullptr;
534   
    bool shutdown_ = false;
575   
    bool shutdown_ = false;
 
576 +
 
577 + 
    static constexpr std::size_t max_service_slots = 32;
 
578 + 
    BOOST_CAPY_MSVC_WARNING_PUSH
 
579 + 
    BOOST_CAPY_MSVC_WARNING_DISABLE(4251)
 
580 + 
    std::atomic<service*> slots_[max_service_slots] = {};
 
581 + 
    BOOST_CAPY_MSVC_WARNING_POP
535   
};
582   
};
536  
583  
537   
template< typename Derived >
584   
template< typename Derived >
538   
execution_context::
585   
execution_context::
539   
execution_context( Derived* ) noexcept
586   
execution_context( Derived* ) noexcept
540   
    : execution_context()
587   
    : execution_context()
541   
{
588   
{
542   
    ti_ = &detail::type_id< Derived >();
589   
    ti_ = &detail::type_id< Derived >();
543   
}
590   
}
544  
591  
545   
} // namespace capy
592   
} // namespace capy
546   
} // namespace boost
593   
} // namespace boost
547  
594  
548   
#endif
595   
#endif