libs/http/include/boost/http/server/detail/dynamic_invoke.hpp
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libs/http/include/boost/http/server/detail/dynamic_invoke.hpp
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|---|---|---|---|
| 1 | // | ||
| 2 | // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com) | ||
| 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/http | ||
| 8 | // | ||
| 9 | |||
| 10 | #ifndef BOOST_HTTP_SERVER_DETAIL_DYNAMIC_INVOKE_HPP | ||
| 11 | #define BOOST_HTTP_SERVER_DETAIL_DYNAMIC_INVOKE_HPP | ||
| 12 | |||
| 13 | #include <boost/http/detail/config.hpp> | ||
| 14 | #include <boost/http/core/polystore.hpp> | ||
| 15 | #include <boost/http/server/route_handler.hpp> | ||
| 16 | #include <tuple> | ||
| 17 | #include <type_traits> | ||
| 18 | #include <utility> | ||
| 19 | |||
| 20 | namespace boost { | ||
| 21 | namespace http { | ||
| 22 | namespace detail { | ||
| 23 | |||
| 24 | //------------------------------------------------ | ||
| 25 | |||
| 26 | template<class... Ts> | ||
| 27 | struct are_unique : std::true_type {}; | ||
| 28 | |||
| 29 | template<class T, class... Ts> | ||
| 30 | struct are_unique<T, Ts...> | ||
| 31 | : std::bool_constant< | ||
| 32 | (!std::is_same_v<T, Ts> && ...) && | ||
| 33 | are_unique<Ts...>::value> {}; | ||
| 34 | |||
| 35 | //------------------------------------------------ | ||
| 36 | |||
| 37 | template<class T> | ||
| 38 | using find_key_t = | ||
| 39 | std::remove_cv_t< | ||
| 40 | std::remove_reference_t<T>>; | ||
| 41 | |||
| 42 | // Polystore lookup key: also strips pointer | ||
| 43 | template<class T> | ||
| 44 | using lookup_key_t = | ||
| 45 | std::remove_cv_t< | ||
| 46 | std::remove_pointer_t< | ||
| 47 | find_key_t<T>>>; | ||
| 48 | |||
| 49 | // True when parameter is a pointer (optional dependency) | ||
| 50 | template<class T> | ||
| 51 | constexpr bool is_optional_v = | ||
| 52 | std::is_pointer_v<find_key_t<T>>; | ||
| 53 | |||
| 54 | // Resolve a polystore pointer to the handler's expected arg | ||
| 55 | template<class Arg, class T> | ||
| 56 | 3 | auto resolve_arg(T* p) | |
| 57 | { | ||
| 58 | if constexpr (is_optional_v<Arg>) | ||
| 59 | 2 | return static_cast<find_key_t<Arg>>(p); | |
| 60 | else | ||
| 61 | 1 | return static_cast<Arg>(*p); | |
| 62 | } | ||
| 63 | |||
| 64 | //------------------------------------------------ | ||
| 65 | |||
| 66 | template<class F, class... Args> | ||
| 67 | route_result | ||
| 68 | dynamic_invoke_impl( | ||
| 69 | polystore& ps, | ||
| 70 | F const& f, | ||
| 71 | type_list<Args...> const&) | ||
| 72 | { | ||
| 73 | static_assert( | ||
| 74 | are_unique<lookup_key_t<Args>...>::value, | ||
| 75 | "callable has duplicate parameter types"); | ||
| 76 | |||
| 77 | auto ptrs = std::make_tuple( | ||
| 78 | ps.find<lookup_key_t<Args>>()...); | ||
| 79 | |||
| 80 | return [&]<std::size_t... I>( | ||
| 81 | std::index_sequence<I...>) -> route_result | ||
| 82 | { | ||
| 83 | if constexpr (!(is_optional_v<Args> && ...)) | ||
| 84 | { | ||
| 85 | if(! (... && (is_optional_v<Args> || | ||
| 86 | std::get<I>(ptrs) != nullptr))) | ||
| 87 | return route_next; | ||
| 88 | } | ||
| 89 | return f(resolve_arg<Args>( | ||
| 90 | std::get<I>(ptrs))...); | ||
| 91 | }(std::index_sequence_for<Args...>{}); | ||
| 92 | } | ||
| 93 | |||
| 94 | /** Invoke a callable, resolving arguments from a polystore. | ||
| 95 | |||
| 96 | Each parameter type of the callable is looked up in the | ||
| 97 | polystore via @ref polystore::find. If all required | ||
| 98 | parameters are found, the callable is invoked with the | ||
| 99 | resolved arguments and its result is returned. If any | ||
| 100 | required parameter is not found, @ref route_next is | ||
| 101 | returned without invoking the callable. | ||
| 102 | |||
| 103 | Parameters declared as pointer types (e.g. `A*`) are | ||
| 104 | optional: `nullptr` is passed when the type is absent. | ||
| 105 | Rvalue reference parameters (e.g. `A&&`) are supported | ||
| 106 | and receive a moved reference to the stored object. | ||
| 107 | |||
| 108 | Duplicate parameter types (after stripping cv-ref and | ||
| 109 | pointer) produce a compile-time error. | ||
| 110 | |||
| 111 | @param ps The polystore to resolve arguments from. | ||
| 112 | @param f The callable to invoke. | ||
| 113 | @return The result of the callable, or @ref route_next | ||
| 114 | if any required parameter was not found. | ||
| 115 | */ | ||
| 116 | template<class F> | ||
| 117 | route_result | ||
| 118 | dynamic_invoke( | ||
| 119 | polystore& ps, | ||
| 120 | F const& f) | ||
| 121 | { | ||
| 122 | return dynamic_invoke_impl( | ||
| 123 | ps, f, | ||
| 124 | typename call_traits< | ||
| 125 | std::decay_t<F>>::arg_types{}); | ||
| 126 | } | ||
| 127 | |||
| 128 | //------------------------------------------------ | ||
| 129 | |||
| 130 | /** Wraps a callable whose first parameter is `route_params&` | ||
| 131 | and whose remaining parameters are resolved from | ||
| 132 | @ref route_params::route_data at dispatch time. | ||
| 133 | |||
| 134 | Produced by @ref dynamic_transform. Stored inside | ||
| 135 | the router's handler table. | ||
| 136 | */ | ||
| 137 | template<class F> | ||
| 138 | struct dynamic_handler | ||
| 139 | { | ||
| 140 | F f; | ||
| 141 | |||
| 142 | // No extra parameters -- just forward to the callable | ||
| 143 | template<class First> | ||
| 144 | route_task | ||
| 145 | 3 | invoke_impl( | |
| 146 | route_params& p, | ||
| 147 | type_list<First> const&) const | ||
| 148 | { | ||
| 149 | static_assert( | ||
| 150 | std::is_convertible_v<route_params&, First>, | ||
| 151 | "first parameter must accept route_params&"); | ||
| 152 | using R = std::invoke_result_t< | ||
| 153 | F const&, route_params&>; | ||
| 154 | if constexpr (std::is_same_v<R, route_task>) | ||
| 155 | return f(p); | ||
| 156 | else | ||
| 157 | 3 | return wrap_result(f(p)); | |
| 158 | } | ||
| 159 | |||
| 160 | static route_task | ||
| 161 | ✗ | make_route_next() | |
| 162 | { | ||
| 163 | co_return route_next; | ||
| 164 | ✗ | } | |
| 165 | |||
| 166 | static route_task | ||
| 167 |
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6 | wrap_result(route_result r) |
| 168 | { | ||
| 169 | co_return r; | ||
| 170 | 12 | } | |
| 171 | |||
| 172 | // Extra parameters resolved from route_data | ||
| 173 | template<class First, class E1, class... Extra> | ||
| 174 | route_task | ||
| 175 | 3 | invoke_impl( | |
| 176 | route_params& p, | ||
| 177 | type_list<First, E1, Extra...> const&) const | ||
| 178 | { | ||
| 179 | static_assert( | ||
| 180 | std::is_convertible_v<route_params&, First>, | ||
| 181 | "first parameter must accept route_params&"); | ||
| 182 |
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3 | return invoke_extras(p, type_list<E1, Extra...>{}); |
| 183 | } | ||
| 184 | |||
| 185 | template<class... Extras> | ||
| 186 | route_task | ||
| 187 | 3 | invoke_extras( | |
| 188 | route_params& p, | ||
| 189 | type_list<Extras...> const&) const | ||
| 190 | { | ||
| 191 | static_assert( | ||
| 192 | are_unique< | ||
| 193 | lookup_key_t<Extras>...>::value, | ||
| 194 | "callable has duplicate parameter types"); | ||
| 195 | |||
| 196 | 3 | auto ptrs = std::make_tuple( | |
| 197 | p.route_data.template find< | ||
| 198 |
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3 | lookup_key_t<Extras>>()...); |
| 199 | |||
| 200 | 3 | return [this, &p, &ptrs]<std::size_t... I>( | |
| 201 | std::index_sequence<I...>) -> route_task | ||
| 202 | { | ||
| 203 | if constexpr (!(is_optional_v<Extras> && ...)) | ||
| 204 | { | ||
| 205 | if(! (... && (is_optional_v<Extras> || | ||
| 206 | std::get<I>(ptrs) != nullptr))) | ||
| 207 | return make_route_next(); | ||
| 208 | } | ||
| 209 | |||
| 210 | using R = std::invoke_result_t< | ||
| 211 | F const&, route_params&, Extras...>; | ||
| 212 | if constexpr (std::is_same_v<R, route_task>) | ||
| 213 | return f(p, resolve_arg<Extras>( | ||
| 214 | std::get<I>(ptrs))...); | ||
| 215 | else | ||
| 216 | return wrap_result(f(p, | ||
| 217 | resolve_arg<Extras>( | ||
| 218 | std::get<I>(ptrs))...)); | ||
| 219 |
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6 | }(std::index_sequence_for<Extras...>{}); |
| 220 | } | ||
| 221 | |||
| 222 | route_task | ||
| 223 | 6 | operator()(route_params& p) const | |
| 224 | { | ||
| 225 | return invoke_impl(p, | ||
| 226 | typename call_traits< | ||
| 227 |
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6 | std::decay_t<F>>::arg_types{}); |
| 228 | } | ||
| 229 | }; | ||
| 230 | |||
| 231 | /** A handler transform that resolves extra parameters from route_data. | ||
| 232 | |||
| 233 | When used with @ref router::with_transform, handlers may | ||
| 234 | declare a first parameter of type `route_params&` followed | ||
| 235 | by additional parameters of arbitrary types. At dispatch time, | ||
| 236 | each extra parameter type is looked up in | ||
| 237 | @ref route_params::route_data via @ref polystore::find. | ||
| 238 | If all required parameters are found the handler is invoked; | ||
| 239 | otherwise @ref route_next is returned. | ||
| 240 | |||
| 241 | Parameters declared as pointer types (e.g. `A*`) are | ||
| 242 | optional: `nullptr` is passed when the type is absent. | ||
| 243 | Rvalue reference parameters (e.g. `A&&`) are supported | ||
| 244 | and receive a moved reference to the stored object. | ||
| 245 | |||
| 246 | Duplicate extra parameter types (after stripping cv-ref | ||
| 247 | and pointer) produce a compile-time error. | ||
| 248 | |||
| 249 | @par Example | ||
| 250 | @code | ||
| 251 | router<route_params> base; | ||
| 252 | auto r = base.with_transform( dynamic_transform{} ); | ||
| 253 | |||
| 254 | r.get( "/users", []( | ||
| 255 | route_params& p, | ||
| 256 | UserService& svc, | ||
| 257 | Config const& cfg) -> route_result | ||
| 258 | { | ||
| 259 | // svc and cfg resolved from p.route_data | ||
| 260 | return route_done; | ||
| 261 | }); | ||
| 262 | @endcode | ||
| 263 | */ | ||
| 264 | struct dynamic_transform | ||
| 265 | { | ||
| 266 | template<class F> | ||
| 267 | auto | ||
| 268 | 6 | operator()(F f) const -> | |
| 269 | dynamic_handler<std::decay_t<F>> | ||
| 270 | { | ||
| 271 | 6 | return { std::move(f) }; | |
| 272 | } | ||
| 273 | }; | ||
| 274 | |||
| 275 | } // detail | ||
| 276 | } // http | ||
| 277 | } // boost | ||
| 278 | |||
| 279 | #endif | ||
| 280 |