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