. /include/boost/corosio /resolver.hpp
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1   // 1   //
2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com) 2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3   // Copyright (c) 2026 Steve Gerbino 3   // Copyright (c) 2026 Steve Gerbino
4   // Copyright (c) 2026 Michael Vandeberg 4   // Copyright (c) 2026 Michael Vandeberg
5   // 5   //
6   // Distributed under the Boost Software License, Version 1.0. (See accompanying 6   // Distributed under the Boost Software License, Version 1.0. (See accompanying
7   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 7   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8   // 8   //
9   // Official repository: https://github.com/cppalliance/corosio 9   // Official repository: https://github.com/cppalliance/corosio
10   // 10   //
11   11  
12   #ifndef BOOST_COROSIO_RESOLVER_HPP 12   #ifndef BOOST_COROSIO_RESOLVER_HPP
13   #define BOOST_COROSIO_RESOLVER_HPP 13   #define BOOST_COROSIO_RESOLVER_HPP
14   14  
15   #include <boost/corosio/detail/config.hpp> 15   #include <boost/corosio/detail/config.hpp>
16   #include <boost/corosio/detail/op_base.hpp> 16   #include <boost/corosio/detail/op_base.hpp>
17   #include <boost/corosio/endpoint.hpp> 17   #include <boost/corosio/endpoint.hpp>
18   #include <boost/corosio/io/io_object.hpp> 18   #include <boost/corosio/io/io_object.hpp>
19   #include <boost/capy/io_result.hpp> 19   #include <boost/capy/io_result.hpp>
20   #include <boost/corosio/resolver_results.hpp> 20   #include <boost/corosio/resolver_results.hpp>
21   #include <boost/capy/ex/executor_ref.hpp> 21   #include <boost/capy/ex/executor_ref.hpp>
22   #include <boost/capy/ex/execution_context.hpp> 22   #include <boost/capy/ex/execution_context.hpp>
23   #include <boost/capy/ex/io_env.hpp> 23   #include <boost/capy/ex/io_env.hpp>
24   #include <boost/capy/concept/executor.hpp> 24   #include <boost/capy/concept/executor.hpp>
25   25  
26   #include <system_error> 26   #include <system_error>
27   27  
28   #include <cassert> 28   #include <cassert>
29   #include <concepts> 29   #include <concepts>
30   #include <coroutine> 30   #include <coroutine>
31   #include <stop_token> 31   #include <stop_token>
32   #include <string> 32   #include <string>
33   #include <string_view> 33   #include <string_view>
34   #include <type_traits> 34   #include <type_traits>
35   35  
36   namespace boost::corosio { 36   namespace boost::corosio {
37   37  
38   /** Bitmask flags for resolver queries. 38   /** Bitmask flags for resolver queries.
39   39  
40   These flags correspond to the hints parameter of getaddrinfo. 40   These flags correspond to the hints parameter of getaddrinfo.
41   */ 41   */
42   enum class resolve_flags : unsigned int 42   enum class resolve_flags : unsigned int
43   { 43   {
44   /// No flags. 44   /// No flags.
45   none = 0, 45   none = 0,
46   46  
47   /// Indicate that returned endpoint is intended for use as a locally 47   /// Indicate that returned endpoint is intended for use as a locally
48   /// bound socket endpoint. 48   /// bound socket endpoint.
49   passive = 0x01, 49   passive = 0x01,
50   50  
51   /// Host name should be treated as a numeric string defining an IPv4 51   /// Host name should be treated as a numeric string defining an IPv4
52   /// or IPv6 address and no name resolution should be attempted. 52   /// or IPv6 address and no name resolution should be attempted.
53   numeric_host = 0x04, 53   numeric_host = 0x04,
54   54  
55   /// Service name should be treated as a numeric string defining a port 55   /// Service name should be treated as a numeric string defining a port
56   /// number and no name resolution should be attempted. 56   /// number and no name resolution should be attempted.
57   numeric_service = 0x08, 57   numeric_service = 0x08,
58   58  
59   /// Only return IPv4 addresses if a non-loopback IPv4 address is 59   /// Only return IPv4 addresses if a non-loopback IPv4 address is
60   /// configured for the system. Only return IPv6 addresses if a 60   /// configured for the system. Only return IPv6 addresses if a
61   /// non-loopback IPv6 address is configured for the system. 61   /// non-loopback IPv6 address is configured for the system.
62   address_configured = 0x20, 62   address_configured = 0x20,
63   63  
64   /// If the query protocol family is specified as IPv6, return 64   /// If the query protocol family is specified as IPv6, return
65   /// IPv4-mapped IPv6 addresses on finding no IPv6 addresses. 65   /// IPv4-mapped IPv6 addresses on finding no IPv6 addresses.
66   v4_mapped = 0x800, 66   v4_mapped = 0x800,
67   67  
68   /// If used with v4_mapped, return all matching IPv6 and IPv4 addresses. 68   /// If used with v4_mapped, return all matching IPv6 and IPv4 addresses.
69   all_matching = 0x100 69   all_matching = 0x100
70   }; 70   };
71   71  
72   /** Combine two resolve_flags. */ 72   /** Combine two resolve_flags. */
73   inline resolve_flags 73   inline resolve_flags
HITCBC 74   17 operator|(resolve_flags a, resolve_flags b) noexcept 74   17 operator|(resolve_flags a, resolve_flags b) noexcept
75   { 75   {
76   return static_cast<resolve_flags>( 76   return static_cast<resolve_flags>(
HITCBC 77   17 static_cast<unsigned int>(a) | static_cast<unsigned int>(b)); 77   17 static_cast<unsigned int>(a) | static_cast<unsigned int>(b));
78   } 78   }
79   79  
80   /** Combine two resolve_flags. */ 80   /** Combine two resolve_flags. */
81   inline resolve_flags& 81   inline resolve_flags&
HITCBC 82   1 operator|=(resolve_flags& a, resolve_flags b) noexcept 82   1 operator|=(resolve_flags& a, resolve_flags b) noexcept
83   { 83   {
HITCBC 84   1 a = a | b; 84   1 a = a | b;
HITCBC 85   1 return a; 85   1 return a;
86   } 86   }
87   87  
88   /** Intersect two resolve_flags. */ 88   /** Intersect two resolve_flags. */
89   inline resolve_flags 89   inline resolve_flags
HITCBC 90   199 operator&(resolve_flags a, resolve_flags b) noexcept 90   199 operator&(resolve_flags a, resolve_flags b) noexcept
91   { 91   {
92   return static_cast<resolve_flags>( 92   return static_cast<resolve_flags>(
HITCBC 93   199 static_cast<unsigned int>(a) & static_cast<unsigned int>(b)); 93   199 static_cast<unsigned int>(a) & static_cast<unsigned int>(b));
94   } 94   }
95   95  
96   /** Intersect two resolve_flags. */ 96   /** Intersect two resolve_flags. */
97   inline resolve_flags& 97   inline resolve_flags&
HITCBC 98   1 operator&=(resolve_flags& a, resolve_flags b) noexcept 98   1 operator&=(resolve_flags& a, resolve_flags b) noexcept
99   { 99   {
HITCBC 100   1 a = a & b; 100   1 a = a & b;
HITCBC 101   1 return a; 101   1 return a;
102   } 102   }
103   103  
104   /** Bitmask flags for reverse resolver queries. 104   /** Bitmask flags for reverse resolver queries.
105   105  
106   These flags correspond to the flags parameter of getnameinfo. 106   These flags correspond to the flags parameter of getnameinfo.
107   */ 107   */
108   enum class reverse_flags : unsigned int 108   enum class reverse_flags : unsigned int
109   { 109   {
110   /// No flags. 110   /// No flags.
111   none = 0, 111   none = 0,
112   112  
113   /// Return the numeric form of the hostname instead of its name. 113   /// Return the numeric form of the hostname instead of its name.
114   numeric_host = 0x01, 114   numeric_host = 0x01,
115   115  
116   /// Return the numeric form of the service name instead of its name. 116   /// Return the numeric form of the service name instead of its name.
117   numeric_service = 0x02, 117   numeric_service = 0x02,
118   118  
119   /// Return an error if the hostname cannot be resolved. 119   /// Return an error if the hostname cannot be resolved.
120   name_required = 0x04, 120   name_required = 0x04,
121   121  
122   /// Lookup for datagram (UDP) service instead of stream (TCP). 122   /// Lookup for datagram (UDP) service instead of stream (TCP).
123   datagram_service = 0x08 123   datagram_service = 0x08
124   }; 124   };
125   125  
126   /** Combine two reverse_flags. */ 126   /** Combine two reverse_flags. */
127   inline reverse_flags 127   inline reverse_flags
HITCBC 128   9 operator|(reverse_flags a, reverse_flags b) noexcept 128   9 operator|(reverse_flags a, reverse_flags b) noexcept
129   { 129   {
130   return static_cast<reverse_flags>( 130   return static_cast<reverse_flags>(
HITCBC 131   9 static_cast<unsigned int>(a) | static_cast<unsigned int>(b)); 131   9 static_cast<unsigned int>(a) | static_cast<unsigned int>(b));
132   } 132   }
133   133  
134   /** Combine two reverse_flags. */ 134   /** Combine two reverse_flags. */
135   inline reverse_flags& 135   inline reverse_flags&
HITCBC 136   1 operator|=(reverse_flags& a, reverse_flags b) noexcept 136   1 operator|=(reverse_flags& a, reverse_flags b) noexcept
137   { 137   {
HITCBC 138   1 a = a | b; 138   1 a = a | b;
HITCBC 139   1 return a; 139   1 return a;
140   } 140   }
141   141  
142   /** Intersect two reverse_flags. */ 142   /** Intersect two reverse_flags. */
143   inline reverse_flags 143   inline reverse_flags
HITCBC 144   79 operator&(reverse_flags a, reverse_flags b) noexcept 144   79 operator&(reverse_flags a, reverse_flags b) noexcept
145   { 145   {
146   return static_cast<reverse_flags>( 146   return static_cast<reverse_flags>(
HITCBC 147   79 static_cast<unsigned int>(a) & static_cast<unsigned int>(b)); 147   79 static_cast<unsigned int>(a) & static_cast<unsigned int>(b));
148   } 148   }
149   149  
150   /** Intersect two reverse_flags. */ 150   /** Intersect two reverse_flags. */
151   inline reverse_flags& 151   inline reverse_flags&
HITCBC 152   1 operator&=(reverse_flags& a, reverse_flags b) noexcept 152   1 operator&=(reverse_flags& a, reverse_flags b) noexcept
153   { 153   {
HITCBC 154   1 a = a & b; 154   1 a = a & b;
HITCBC 155   1 return a; 155   1 return a;
156   } 156   }
157   157  
158   /** An asynchronous DNS resolver for coroutine I/O. 158   /** An asynchronous DNS resolver for coroutine I/O.
159   159  
160   This class provides asynchronous DNS resolution operations that return 160   This class provides asynchronous DNS resolution operations that return
161   awaitable types. Each operation participates in the affine awaitable 161   awaitable types. Each operation participates in the affine awaitable
162   protocol, ensuring coroutines resume on the correct executor. 162   protocol, ensuring coroutines resume on the correct executor.
163   163  
164   @par Thread Safety 164   @par Thread Safety
165   Distinct objects: Safe.@n 165   Distinct objects: Safe.@n
166   Shared objects: Unsafe. A resolver must not have concurrent resolve 166   Shared objects: Unsafe. A resolver must not have concurrent resolve
167   operations. 167   operations.
168   168  
169   @par Semantics 169   @par Semantics
170   Wraps platform DNS resolution (getaddrinfo/getnameinfo). 170   Wraps platform DNS resolution (getaddrinfo/getnameinfo).
171   Operations dispatch to OS resolver APIs via the io_context 171   Operations dispatch to OS resolver APIs via the io_context
172   thread pool. 172   thread pool.
173   173  
174   @par Example 174   @par Example
175   @par !example resolver 175   @par !example resolver
176   */ 176   */
177   class BOOST_COROSIO_DECL resolver : public io_object 177   class BOOST_COROSIO_DECL resolver : public io_object
178   { 178   {
179   struct resolve_awaitable 179   struct resolve_awaitable
180   : detail::value_op_base<resolve_awaitable, resolver_results> 180   : detail::value_op_base<resolve_awaitable, resolver_results>
181   { 181   {
182   resolver& r_; 182   resolver& r_;
183   std::string host_; 183   std::string host_;
184   std::string service_; 184   std::string service_;
185   resolve_flags flags_; 185   resolve_flags flags_;
186   186  
HITCBC 187   30 resolve_awaitable( 187   30 resolve_awaitable(
188   resolver& r, 188   resolver& r,
189   std::string_view host, 189   std::string_view host,
190   std::string_view service, 190   std::string_view service,
191   resolve_flags flags) noexcept 191   resolve_flags flags) noexcept
HITCBC 192   60 : r_(r) 192   60 : r_(r)
HITCBC 193   60 , host_(host) 193   60 , host_(host)
HITCBC 194   60 , service_(service) 194   60 , service_(service)
HITCBC 195   30 , flags_(flags) 195   30 , flags_(flags)
196   { 196   {
HITCBC 197   30 } 197   30 }
198   198  
HITGIC 199 - std::coroutine_handle<> 199 + 30 std::coroutine_handle<> dispatch(
ECB 200 - 30 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const 200 + std::coroutine_handle<> h, capy::executor_ref ex) const
201   { 201   {
HITCBC 202   90 return r_.get().resolve( 202   90 return r_.get().resolve(
HITCBC 203   90 h, ex, host_, service_, flags_, token_, &ec_, &value_); 203   90 h, ex, host_, service_, flags_, token_, &ec_, &value_);
204   } 204   }
205   }; 205   };
206   206  
207   struct reverse_resolve_awaitable 207   struct reverse_resolve_awaitable
208 - : detail:: 208 + : detail::value_op_base<reverse_resolve_awaitable, reverse_resolver_result>
209 - value_op_base<reverse_resolve_awaitable, reverse_resolver_result>  
210   { 209   {
211   resolver& r_; 210   resolver& r_;
212   endpoint ep_; 211   endpoint ep_;
213   reverse_flags flags_; 212   reverse_flags flags_;
214   213  
HITCBC 215   20 reverse_resolve_awaitable( 214   20 reverse_resolve_awaitable(
216   resolver& r, endpoint const& ep, reverse_flags flags) noexcept 215   resolver& r, endpoint const& ep, reverse_flags flags) noexcept
HITCBC 217   40 : r_(r) 216   40 : r_(r)
HITCBC 218   20 , ep_(ep) 217   20 , ep_(ep)
HITCBC 219   20 , flags_(flags) 218   20 , flags_(flags)
220   { 219   {
HITCBC 221   20 } 220   20 }
222   221  
HITGIC 223 - std::coroutine_handle<> 222 + 20 std::coroutine_handle<> dispatch(
ECB 224 - 20 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const 223 + std::coroutine_handle<> h, capy::executor_ref ex) const
225   { 224   {
HITCBC 226   40 return r_.get().reverse_resolve( 225   40 return r_.get().reverse_resolve(
HITCBC 227   40 h, ex, ep_, flags_, token_, &ec_, &value_); 226   40 h, ex, ep_, flags_, token_, &ec_, &value_);
228   } 227   }
229   }; 228   };
230   229  
231   public: 230   public:
232   /** Destructor. 231   /** Destructor.
233   232  
234   Cancels any pending operations. 233   Cancels any pending operations.
235   */ 234   */
236   ~resolver() override; 235   ~resolver() override;
237   236  
238   /** Construct a resolver from an execution context. 237   /** Construct a resolver from an execution context.
239   238  
240   @param ctx The execution context that will own this resolver. 239   @param ctx The execution context that will own this resolver.
241   */ 240   */
242   explicit resolver(capy::execution_context& ctx); 241   explicit resolver(capy::execution_context& ctx);
243   242  
244   /** Construct a resolver from an executor. 243   /** Construct a resolver from an executor.
245   244  
246   The resolver is associated with the executor's context. 245   The resolver is associated with the executor's context.
247   246  
248   @param ex The executor whose context will own the resolver. 247   @param ex The executor whose context will own the resolver.
249   */ 248   */
250   template<class Ex> 249   template<class Ex>
251   requires(!std::same_as<std::remove_cvref_t<Ex>, resolver>) && 250   requires(!std::same_as<std::remove_cvref_t<Ex>, resolver>) &&
252   capy::Executor<Ex> 251   capy::Executor<Ex>
HITCBC 253   1 explicit resolver(Ex const& ex) : resolver(ex.context()) 252   1 explicit resolver(Ex const& ex) : resolver(ex.context())
254   { 253   {
HITCBC 255   1 } 254   1 }
256   255  
257   /** Move constructor. 256   /** Move constructor.
258   257  
259   Transfers ownership of the resolver resources. After the move, 258   Transfers ownership of the resolver resources. After the move,
260   @p other is in a moved-from state and may only be destroyed or 259   @p other is in a moved-from state and may only be destroyed or
261   assigned to. 260   assigned to.
262   261  
263   @param other The resolver to move from. 262   @param other The resolver to move from.
264   263  
265   @pre No awaitables returned by @p other's `resolve` methods 264   @pre No awaitables returned by @p other's `resolve` methods
266   exist. 265   exist.
267   @pre The execution context associated with @p other must 266   @pre The execution context associated with @p other must
268   outlive this resolver. 267   outlive this resolver.
269   */ 268   */
HITCBC 270   2 resolver(resolver&& other) noexcept : io_object(std::move(other)) {} 269   2 resolver(resolver&& other) noexcept : io_object(std::move(other)) {}
271   270  
272   /** Move assignment operator. 271   /** Move assignment operator.
273   272  
274   Destroys the current implementation and transfers ownership 273   Destroys the current implementation and transfers ownership
275   from @p other. After the move, @p other is in a moved-from 274   from @p other. After the move, @p other is in a moved-from
276   state and may only be destroyed or assigned to. 275   state and may only be destroyed or assigned to.
277   276  
278   @param other The resolver to move from. 277   @param other The resolver to move from.
279   278  
280   @pre No awaitables returned by either `*this` or @p other's 279   @pre No awaitables returned by either `*this` or @p other's
281   `resolve` methods exist. 280   `resolve` methods exist.
282   @pre The execution context associated with @p other must 281   @pre The execution context associated with @p other must
283   outlive this resolver. 282   outlive this resolver.
284   283  
285   @return Reference to this resolver. 284   @return Reference to this resolver.
286   */ 285   */
HITCBC 287   2 resolver& operator=(resolver&& other) noexcept 286   2 resolver& operator=(resolver&& other) noexcept
288   { 287   {
HITCBC 289   2 if (this != &other) 288   2 if (this != &other)
HITCBC 290   2 h_ = std::move(other.h_); 289   2 h_ = std::move(other.h_);
HITCBC 291   2 return *this; 290   2 return *this;
292   } 291   }
293   292  
294   resolver(resolver const&) = delete; 293   resolver(resolver const&) = delete;
295   resolver& operator=(resolver const&) = delete; 294   resolver& operator=(resolver const&) = delete;
296   295  
297   /** Initiate an asynchronous resolve operation. 296   /** Initiate an asynchronous resolve operation.
298   297  
299   Resolves the host and service names into a list of endpoints. 298   Resolves the host and service names into a list of endpoints.
300   299  
301   This resolver must outlive the returned awaitable. 300   This resolver must outlive the returned awaitable.
302   301  
303   @param host A string identifying a location. May be a descriptive 302   @param host A string identifying a location. May be a descriptive
304   name or a numeric address string. 303   name or a numeric address string.
305   304  
306   @param service A string identifying the requested service. This may 305   @param service A string identifying the requested service. This may
307   be a descriptive name or a numeric string corresponding to a 306   be a descriptive name or a numeric string corresponding to a
308   port number. 307   port number.
309   308  
310   @return An awaitable that completes with `io_result<resolver_results>`. 309   @return An awaitable that completes with `io_result<resolver_results>`.
311   310  
312   @note `resolver_results` is an alias for `std::vector<resolver_entry>`. 311   @note `resolver_results` is an alias for `std::vector<resolver_entry>`.
313   Copying it deep-copies every entry (each owns two `std::string`s); 312   Copying it deep-copies every entry (each owns two `std::string`s);
314   move it (`std::move(results)`) or pass iterators when handing it to 313   move it (`std::move(results)`) or pass iterators when handing it to
315   a by-value sink such as @ref connect. 314   a by-value sink such as @ref connect.
316   315  
317   @par Example 316   @par Example
318   @par !example forward_resolve 317   @par !example forward_resolve
319   */ 318   */
HITCBC 320   14 [[nodiscard]] auto resolve(std::string_view host, std::string_view service) 319   14 [[nodiscard]] auto resolve(std::string_view host, std::string_view service)
321   { 320   {
HITCBC 322   14 return resolve_awaitable(*this, host, service, resolve_flags::none); 321   14 return resolve_awaitable(*this, host, service, resolve_flags::none);
323   } 322   }
324   323  
325   /** Initiate an asynchronous resolve operation with flags. 324   /** Initiate an asynchronous resolve operation with flags.
326   325  
327   Resolves the host and service names into a list of endpoints. 326   Resolves the host and service names into a list of endpoints.
328   327  
329   This resolver must outlive the returned awaitable. 328   This resolver must outlive the returned awaitable.
330   329  
331   @param host A string identifying a location. 330   @param host A string identifying a location.
332   331  
333   @param service A string identifying the requested service. 332   @param service A string identifying the requested service.
334   333  
335   @param flags Flags controlling resolution behavior. 334   @param flags Flags controlling resolution behavior.
336   335  
337   @return An awaitable that completes with `io_result<resolver_results>`. 336   @return An awaitable that completes with `io_result<resolver_results>`.
338   */ 337   */
HITCBC 339   16 [[nodiscard]] auto resolve( 338   16 [[nodiscard]] auto resolve(
340   std::string_view host, std::string_view service, resolve_flags flags) 339   std::string_view host, std::string_view service, resolve_flags flags)
341   { 340   {
HITCBC 342   16 return resolve_awaitable(*this, host, service, flags); 341   16 return resolve_awaitable(*this, host, service, flags);
343   } 342   }
344   343  
345   /** Initiate an asynchronous reverse resolve operation. 344   /** Initiate an asynchronous reverse resolve operation.
346   345  
347   Resolves an endpoint into a hostname and service name using 346   Resolves an endpoint into a hostname and service name using
348   reverse DNS lookup (PTR record query). 347   reverse DNS lookup (PTR record query).
349   348  
350   This resolver must outlive the returned awaitable. 349   This resolver must outlive the returned awaitable.
351   350  
352   @param ep The endpoint to resolve. 351   @param ep The endpoint to resolve.
353   352  
354   @return An awaitable that completes with 353   @return An awaitable that completes with
355   `io_result<reverse_resolver_result>`. 354   `io_result<reverse_resolver_result>`.
356   355  
357   @par Example 356   @par Example
358   @par !example reverse_resolve 357   @par !example reverse_resolve
359   */ 358   */
HITCBC 360   11 [[nodiscard]] auto resolve(endpoint const& ep) 359   11 [[nodiscard]] auto resolve(endpoint const& ep)
361   { 360   {
HITCBC 362   11 return reverse_resolve_awaitable(*this, ep, reverse_flags::none); 361   11 return reverse_resolve_awaitable(*this, ep, reverse_flags::none);
363   } 362   }
364   363  
365   /** Initiate an asynchronous reverse resolve operation with flags. 364   /** Initiate an asynchronous reverse resolve operation with flags.
366   365  
367   Resolves an endpoint into a hostname and service name using 366   Resolves an endpoint into a hostname and service name using
368   reverse DNS lookup (PTR record query). 367   reverse DNS lookup (PTR record query).
369   368  
370   This resolver must outlive the returned awaitable. 369   This resolver must outlive the returned awaitable.
371   370  
372   @param ep The endpoint to resolve. 371   @param ep The endpoint to resolve.
373   372  
374   @param flags Flags controlling resolution behavior. See reverse_flags. 373   @param flags Flags controlling resolution behavior. See reverse_flags.
375   374  
376   @return An awaitable that completes with 375   @return An awaitable that completes with
377   `io_result<reverse_resolver_result>`. 376   `io_result<reverse_resolver_result>`.
378   */ 377   */
HITCBC 379   9 [[nodiscard]] auto resolve(endpoint const& ep, reverse_flags flags) 378   9 [[nodiscard]] auto resolve(endpoint const& ep, reverse_flags flags)
380   { 379   {
HITCBC 381   9 return reverse_resolve_awaitable(*this, ep, flags); 380   9 return reverse_resolve_awaitable(*this, ep, flags);
382   } 381   }
383   382  
384   /** Cancel any pending asynchronous operations. 383   /** Cancel any pending asynchronous operations.
385   384  
386   All outstanding operations complete with `errc::operation_canceled`. 385   All outstanding operations complete with `errc::operation_canceled`.
387   Check `ec == cond::canceled` for portable comparison. 386   Check `ec == cond::canceled` for portable comparison.
388   */ 387   */
389   void cancel() noexcept; 388   void cancel() noexcept;
390   389  
391   public: 390   public:
392   /** Backend interface for DNS resolution operations. 391   /** Backend interface for DNS resolution operations.
393   392  
394   Platform backends derive from this to implement forward and 393   Platform backends derive from this to implement forward and
395   reverse DNS resolution via getaddrinfo/getnameinfo. 394   reverse DNS resolution via getaddrinfo/getnameinfo.
396   */ 395   */
397   struct implementation : io_object::implementation 396   struct implementation : io_object::implementation
398   { 397   {
399   /// Initiate an asynchronous forward DNS resolution. 398   /// Initiate an asynchronous forward DNS resolution.
400   virtual std::coroutine_handle<> resolve( 399   virtual std::coroutine_handle<> resolve(
401   std::coroutine_handle<>, 400   std::coroutine_handle<>,
402   capy::executor_ref, 401   capy::executor_ref,
403   std::string_view host, 402   std::string_view host,
404   std::string_view service, 403   std::string_view service,
405   resolve_flags flags, 404   resolve_flags flags,
406   std::stop_token, 405   std::stop_token,
407   std::error_code*, 406   std::error_code*,
408   resolver_results*) = 0; 407   resolver_results*) = 0;
409   408  
410   /// Initiate an asynchronous reverse DNS resolution. 409   /// Initiate an asynchronous reverse DNS resolution.
411   virtual std::coroutine_handle<> reverse_resolve( 410   virtual std::coroutine_handle<> reverse_resolve(
412   std::coroutine_handle<>, 411   std::coroutine_handle<>,
413   capy::executor_ref, 412   capy::executor_ref,
414   endpoint const& ep, 413   endpoint const& ep,
415   reverse_flags flags, 414   reverse_flags flags,
416   std::stop_token, 415   std::stop_token,
417   std::error_code*, 416   std::error_code*,
418   reverse_resolver_result*) = 0; 417   reverse_resolver_result*) = 0;
419   418  
420   /// Cancel pending resolve operations. 419   /// Cancel pending resolve operations.
421   virtual void cancel() noexcept = 0; 420   virtual void cancel() noexcept = 0;
422   }; 421   };
423   422  
424   protected: 423   protected:
425   explicit resolver(handle h) noexcept : io_object(std::move(h)) {} 424   explicit resolver(handle h) noexcept : io_object(std::move(h)) {}
426   425  
427   private: 426   private:
HITCBC 428   57 inline implementation& get() const noexcept 427   57 inline implementation& get() const noexcept
429   { 428   {
HITCBC 430   57 return *static_cast<implementation*>(h_.get()); 429   57 return *static_cast<implementation*>(h_.get());
431   } 430   }
432   }; 431   };
433   432  
434   } // namespace boost::corosio 433   } // namespace boost::corosio
435   434  
436   #endif 435   #endif