. /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/capy/ex/executor_ref.hpp> 20   #include <boost/capy/ex/executor_ref.hpp>
21   #include <boost/capy/ex/execution_context.hpp> 21   #include <boost/capy/ex/execution_context.hpp>
22   #include <boost/capy/ex/io_env.hpp> 22   #include <boost/capy/ex/io_env.hpp>
23   #include <boost/capy/concept/executor.hpp> 23   #include <boost/capy/concept/executor.hpp>
24   24  
25   #include <system_error> 25   #include <system_error>
26   26  
27   #include <cassert> 27   #include <cassert>
28   #include <concepts> 28   #include <concepts>
29   #include <coroutine> 29   #include <coroutine>
30   #include <stop_token> 30   #include <stop_token>
31   #include <string> 31   #include <string>
32   #include <string_view> 32   #include <string_view>
33   #include <vector> 33   #include <vector>
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   205 operator&(resolve_flags a, resolve_flags b) noexcept 90   205 operator&(resolve_flags a, resolve_flags b) noexcept
91   { 91   {
92   return static_cast<resolve_flags>( 92   return static_cast<resolve_flags>(
HITCBC 93   205 static_cast<unsigned int>(a) & static_cast<unsigned int>(b)); 93   205 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   75 operator&(reverse_flags a, reverse_flags b) noexcept 144   75 operator&(reverse_flags a, reverse_flags b) noexcept
145   { 145   {
146   return static_cast<reverse_flags>( 146   return static_cast<reverse_flags>(
HITCBC 147   75 static_cast<unsigned int>(a) & static_cast<unsigned int>(b)); 147   75 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   /** The name of an endpoint. 158   /** The name of an endpoint.
159   159  
160   Reverse resolution translates an endpoint into its symbolic 160   Reverse resolution translates an endpoint into its symbolic
161   spelling: the host name and the service name. Both fields carry 161   spelling: the host name and the service name. Both fields carry
162   resolved data; the endpoint they name is the one the caller 162   resolved data; the endpoint they name is the one the caller
163   passed to `resolve`. 163   passed to `resolve`.
164   */ 164   */
165   struct endpoint_name 165   struct endpoint_name
166   { 166   {
167   /// The resolved host name. 167   /// The resolved host name.
168   std::string host_name; 168   std::string host_name;
169   169  
170   /// The resolved service name. 170   /// The resolved service name.
171   std::string service_name; 171   std::string service_name;
172   }; 172   };
173   173  
174 - /** An asynchronous DNS resolver for coroutine I/O. 174 + /** Resolves host names and services to endpoints, from a coroutine.
175   175  
176   This class provides asynchronous DNS resolution operations that return 176   This class provides asynchronous DNS resolution operations that return
177   awaitable types. Each operation participates in the affine awaitable 177   awaitable types. Each operation participates in the affine awaitable
178   protocol, ensuring coroutines resume on the correct executor. 178   protocol, ensuring coroutines resume on the correct executor.
179   179  
180   @par Thread Safety 180   @par Thread Safety
181   Distinct objects: Safe.@n 181   Distinct objects: Safe.@n
182   Shared objects: Unsafe. A resolver must not have concurrent resolve 182   Shared objects: Unsafe. A resolver must not have concurrent resolve
183   operations. 183   operations.
184   184  
185   @par Semantics 185   @par Semantics
186 - Wraps platform DNS resolution (getaddrinfo/getnameinfo). 186 + Wraps platform DNS resolution (`getaddrinfo`/`getnameinfo`).
187 - Operations dispatch to OS resolver APIs via the io_context 187 + Operations dispatch to OS resolver APIs via the `io_context`
188   thread pool. 188   thread pool.
189   189  
190   @par Example 190   @par Example
191   @par !example resolver 191   @par !example resolver
192   */ 192   */
193   class BOOST_COROSIO_DECL resolver : public io_object 193   class BOOST_COROSIO_DECL resolver : public io_object
194   { 194   {
195   struct resolve_awaitable 195   struct resolve_awaitable
196   : detail::value_op_base<resolve_awaitable, std::vector<endpoint>> 196   : detail::value_op_base<resolve_awaitable, std::vector<endpoint>>
197   { 197   {
198 - resolver& r_; 198 + private:
199 - std::string host_; 199 + friend resolver;
200 - std::string service_;  
201 - resolve_flags flags_;  
202   200  
HITCBC 203   29 resolve_awaitable( 201   29 resolve_awaitable(
204   resolver& r, 202   resolver& r,
205   std::string_view host, 203   std::string_view host,
206   std::string_view service, 204   std::string_view service,
207   resolve_flags flags) noexcept 205   resolve_flags flags) noexcept
HITCBC 208   58 : r_(r) 206   58 : r_(r)
HITCBC 209   58 , host_(host) 207   58 , host_(host)
HITCBC 210   58 , service_(service) 208   58 , service_(service)
HITCBC 211   29 , flags_(flags) 209   29 , flags_(flags)
212   { 210   {
HITCBC 213   29 } 211   29 }
214   212  
  213 + friend detail::value_op_base<resolve_awaitable, std::vector<endpoint>>;
  214 + resolver& r_;
  215 + std::string host_;
  216 + std::string service_;
  217 + resolve_flags flags_;
  218 +
215   std::coroutine_handle<> 219   std::coroutine_handle<>
HITCBC 216   28 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const 220   28 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
217   { 221   {
HITCBC 218   84 return r_.get().resolve( 222   84 return r_.get().resolve(
HITCBC 219   84 h, ex, host_, service_, flags_, token_, &ec_, &value_); 223   84 h, ex, host_, service_, flags_, token_, &ec_, &value_);
220   } 224   }
221   }; 225   };
222   226  
223   struct resolve_host_awaitable 227   struct resolve_host_awaitable
224   : detail::value_op_base<resolve_host_awaitable, std::vector<endpoint>> 228   : detail::value_op_base<resolve_host_awaitable, std::vector<endpoint>>
225   { 229   {
226 - resolver& r_; 230 + private:
227 - std::string host_; 231 + friend resolver;
228 - resolve_flags flags_;  
229   232  
HITCBC 230   6 resolve_host_awaitable( 233   6 resolve_host_awaitable(
231   resolver& r, std::string_view host, resolve_flags flags) noexcept 234   resolver& r, std::string_view host, resolve_flags flags) noexcept
HITCBC 232   12 : r_(r) 235   12 : r_(r)
HITCBC 233   12 , host_(host) 236   12 , host_(host)
HITCBC 234   6 , flags_(flags) 237   6 , flags_(flags)
235   { 238   {
HITCBC 236   6 } 239   6 }
237   240  
  241 + friend detail::
  242 + value_op_base<resolve_host_awaitable, std::vector<endpoint>>;
  243 + resolver& r_;
  244 + std::string host_;
  245 + resolve_flags flags_;
  246 +
238   std::coroutine_handle<> 247   std::coroutine_handle<>
HITCBC 239   5 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const 248   5 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
240   { 249   {
241   // An empty service reaches the system resolver as null, 250   // An empty service reaches the system resolver as null,
242   // which is the host-only query 251   // which is the host-only query
HITCBC 243   15 return r_.get().resolve( 252   15 return r_.get().resolve(
HITCBC 244   15 h, ex, host_, {}, flags_, token_, &ec_, &value_); 253   15 h, ex, host_, {}, flags_, token_, &ec_, &value_);
245   } 254   }
246   255  
  256 + public:
247   // Shadows the base: the endpoint result is reshaped into 257   // Shadows the base: the endpoint result is reshaped into
248   // the honest address list 258   // the honest address list
249   [[nodiscard]] capy::io_result<std::vector<ip_address>> 259   [[nodiscard]] capy::io_result<std::vector<ip_address>>
HITCBC 250   6 await_resume() const 260   6 await_resume() const
251   { 261   {
HITCBC 252   6 std::vector<ip_address> addrs; 262   6 std::vector<ip_address> addrs;
HITCBC 253   6 addrs.reserve(value_.size()); 263   6 addrs.reserve(value_.size());
HITCBC 254   9 for (auto const& entry : value_) 264   9 for (auto const& entry : value_)
255   { 265   {
HITCBC 256   3 auto a = entry.address(); 266   3 auto a = entry.address();
HITCBC 257   3 bool duplicate = false; 267   3 bool duplicate = false;
HITCBC 258   3 for (auto const& seen : addrs) 268   3 for (auto const& seen : addrs)
259   { 269   {
MISUBC 260   ✗ if (seen == a) 270   ✗ if (seen == a)
261   { 271   {
MISUBC 262   ✗ duplicate = true; 272   ✗ duplicate = true;
MISUBC 263   ✗ break; 273   ✗ break;
264   } 274   }
265   } 275   }
266   // The same address can come back more than once 276   // The same address can come back more than once
267   // (mixed name sources, repeated records); each 277   // (mixed name sources, repeated records); each
268   // address is reported once 278   // address is reported once
HITCBC 269   3 if (!duplicate) 279   3 if (!duplicate)
HITCBC 270   3 addrs.push_back(a); 280   3 addrs.push_back(a);
271   } 281   }
HITCBC 272   12 return {ec_, std::move(addrs)}; 282   12 return {ec_, std::move(addrs)};
HITCBC 273   6 } 283   6 }
274   }; 284   };
275   285  
276   struct reverse_resolve_awaitable 286   struct reverse_resolve_awaitable
277   : detail::value_op_base<reverse_resolve_awaitable, endpoint_name> 287   : detail::value_op_base<reverse_resolve_awaitable, endpoint_name>
278   { 288   {
279 - resolver& r_; 289 + private:
280 - endpoint ep_; 290 + friend resolver;
281 - reverse_flags flags_;  
282   291  
HITCBC 283   20 reverse_resolve_awaitable( 292   20 reverse_resolve_awaitable(
284   resolver& r, endpoint const& ep, reverse_flags flags) noexcept 293   resolver& r, endpoint const& ep, reverse_flags flags) noexcept
HITCBC 285   40 : r_(r) 294   40 : r_(r)
HITCBC 286   20 , ep_(ep) 295   20 , ep_(ep)
HITCBC 287   20 , flags_(flags) 296   20 , flags_(flags)
288   { 297   {
HITCBC 289   20 } 298   20 }
290   299  
  300 + friend detail::value_op_base<reverse_resolve_awaitable, endpoint_name>;
  301 +
  302 + resolver& r_;
  303 + endpoint ep_;
  304 + reverse_flags flags_;
  305 +
291   std::coroutine_handle<> 306   std::coroutine_handle<>
HITCBC 292   19 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const 307   19 dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
293   { 308   {
HITCBC 294   38 return r_.get().reverse_resolve( 309   38 return r_.get().reverse_resolve(
HITCBC 295   38 h, ex, ep_, flags_, token_, &ec_, &value_); 310   38 h, ex, ep_, flags_, token_, &ec_, &value_);
296   } 311   }
297   }; 312   };
298   313  
299   public: 314   public:
300   /** Destructor. 315   /** Destructor.
301   316  
302   Cancels any pending operations. 317   Cancels any pending operations.
303   */ 318   */
304   ~resolver() override; 319   ~resolver() override;
305   320  
306   /** Construct a resolver from an execution context. 321   /** Construct a resolver from an execution context.
307   322  
308 - @param ctx The execution context that will own this resolver. 323 + @param ctx The execution context that owns this resolver.
309   */ 324   */
310   explicit resolver(capy::execution_context& ctx); 325   explicit resolver(capy::execution_context& ctx);
311   326  
312   /** Construct a resolver from an executor. 327   /** Construct a resolver from an executor.
313   328  
314   The resolver is associated with the executor's context. 329   The resolver is associated with the executor's context.
315   330  
316 - @param ex The executor whose context will own the resolver. 331 + @param ex The executor whose context owns the resolver.
317   */ 332   */
318   template<class Ex> 333   template<class Ex>
319   requires(!std::same_as<std::remove_cvref_t<Ex>, resolver>) && 334   requires(!std::same_as<std::remove_cvref_t<Ex>, resolver>) &&
320   capy::Executor<Ex> 335   capy::Executor<Ex>
HITCBC 321   1 explicit resolver(Ex const& ex) : resolver(ex.context()) 336   1 explicit resolver(Ex const& ex) : resolver(ex.context())
322   { 337   {
HITCBC 323   1 } 338   1 }
324   339  
325   /** Move constructor. 340   /** Move constructor.
326   341  
327   Transfers ownership of the resolver resources. After the move, 342   Transfers ownership of the resolver resources. After the move,
328   @p other is in a moved-from state and may only be destroyed or 343   @p other is in a moved-from state and may only be destroyed or
329   assigned to. 344   assigned to.
330   345  
331   @param other The resolver to move from. 346   @param other The resolver to move from.
332   347  
333   @pre No awaitables returned by @p other's `resolve` methods 348   @pre No awaitables returned by @p other's `resolve` methods
334   exist. 349   exist.
335   @pre The execution context associated with @p other must 350   @pre The execution context associated with @p other must
336   outlive this resolver. 351   outlive this resolver.
337   */ 352   */
HITCBC 338   2 resolver(resolver&& other) noexcept : io_object(std::move(other)) {} 353   2 resolver(resolver&& other) noexcept : io_object(std::move(other)) {}
339   354  
340   /** Move assignment operator. 355   /** Move assignment operator.
341   356  
342   Destroys the current implementation and transfers ownership 357   Destroys the current implementation and transfers ownership
343   from @p other. After the move, @p other is in a moved-from 358   from @p other. After the move, @p other is in a moved-from
344   state and may only be destroyed or assigned to. 359   state and may only be destroyed or assigned to.
345   360  
346   @param other The resolver to move from. 361   @param other The resolver to move from.
347   362  
348   @pre No awaitables returned by either `*this` or @p other's 363   @pre No awaitables returned by either `*this` or @p other's
349   `resolve` methods exist. 364   `resolve` methods exist.
350   @pre The execution context associated with @p other must 365   @pre The execution context associated with @p other must
351   outlive this resolver. 366   outlive this resolver.
352   367  
353   @return Reference to this resolver. 368   @return Reference to this resolver.
354   */ 369   */
HITCBC 355   2 resolver& operator=(resolver&& other) noexcept 370   2 resolver& operator=(resolver&& other) noexcept
356   { 371   {
HITCBC 357   2 if (this != &other) 372   2 if (this != &other)
HITCBC 358   2 h_ = std::move(other.h_); 373   2 h_ = std::move(other.h_);
HITCBC 359   2 return *this; 374   2 return *this;
360   } 375   }
361   376  
362 - resolver(resolver const&) = delete; 377 + /// Copy construction is disabled; the handle is uniquely owned.
  378 + resolver(resolver const&) = delete;
  379 + /// Copy assignment is disabled; the handle is uniquely owned.
363   resolver& operator=(resolver const&) = delete; 380   resolver& operator=(resolver const&) = delete;
364   381  
365   /** Initiate an asynchronous resolve operation. 382   /** Initiate an asynchronous resolve operation.
366   383  
367   Resolves the host and service names into a list of endpoints. 384   Resolves the host and service names into a list of endpoints.
368   385  
369   This resolver must outlive the returned awaitable. 386   This resolver must outlive the returned awaitable.
370   387  
371   @param host A string identifying a location. May be a descriptive 388   @param host A string identifying a location. May be a descriptive
372   name or a numeric address string. 389   name or a numeric address string.
373   390  
374   @param service A string identifying the requested service. This may 391   @param service A string identifying the requested service. This may
375   be a descriptive name or a numeric string corresponding to a 392   be a descriptive name or a numeric string corresponding to a
376   port number. 393   port number.
377   394  
378   @return An awaitable that completes with 395   @return An awaitable that completes with
379   `io_result<std::vector<endpoint>>`. 396   `io_result<std::vector<endpoint>>`.
380   397  
381   @par Example 398   @par Example
382   @par !example forward_resolve 399   @par !example forward_resolve
383   */ 400   */
HITCBC 384   13 [[nodiscard]] auto resolve(std::string_view host, std::string_view service) 401   13 [[nodiscard]] auto resolve(std::string_view host, std::string_view service)
385   { 402   {
HITCBC 386   13 return resolve_awaitable(*this, host, service, resolve_flags::none); 403   13 return resolve_awaitable(*this, host, service, resolve_flags::none);
387   } 404   }
388   405  
389   /** Initiate an asynchronous host-only resolve operation. 406   /** Initiate an asynchronous host-only resolve operation.
390   407  
391   Resolves a host name into its addresses, with no service or 408   Resolves a host name into its addresses, with no service or
392   port involved — the query `getaddrinfo` performs with a null 409   port involved — the query `getaddrinfo` performs with a null
393   service. Use this when the host and port travel separately, 410   service. Use this when the host and port travel separately,
394   as they do in most configuration. 411   as they do in most configuration.
395   412  
396   Each address appears once in the result even when the query 413   Each address appears once in the result even when the query
397   reports it more than once, and link-local results keep 414   reports it more than once, and link-local results keep
398   their zone. 415   their zone.
399   416  
400   @param host The host name or numeric address string. 417   @param host The host name or numeric address string.
401   418  
402   @return An awaitable that completes with 419   @return An awaitable that completes with
403   `io_result<std::vector<ip_address>>`. 420   `io_result<std::vector<ip_address>>`.
404   421  
405   @par Example 422   @par Example
406   @par !example host_only_resolve 423   @par !example host_only_resolve
407   */ 424   */
HITCBC 408   3 [[nodiscard]] auto resolve(std::string_view host) 425   3 [[nodiscard]] auto resolve(std::string_view host)
409   { 426   {
HITCBC 410   3 return resolve_host_awaitable(*this, host, resolve_flags::none); 427   3 return resolve_host_awaitable(*this, host, resolve_flags::none);
411   } 428   }
412   429  
413   /** Initiate an asynchronous host-only resolve operation with flags. 430   /** Initiate an asynchronous host-only resolve operation with flags.
414   431  
415   @param host The host name or numeric address string. 432   @param host The host name or numeric address string.
416   @param flags Resolution behavior flags. 433   @param flags Resolution behavior flags.
417   434  
418   @return An awaitable that completes with 435   @return An awaitable that completes with
419   `io_result<std::vector<ip_address>>`. 436   `io_result<std::vector<ip_address>>`.
420   */ 437   */
HITCBC 421   3 [[nodiscard]] auto resolve(std::string_view host, resolve_flags flags) 438   3 [[nodiscard]] auto resolve(std::string_view host, resolve_flags flags)
422   { 439   {
HITCBC 423   3 return resolve_host_awaitable(*this, host, flags); 440   3 return resolve_host_awaitable(*this, host, flags);
424   } 441   }
425   442  
426   /** Initiate an asynchronous resolve operation with flags. 443   /** Initiate an asynchronous resolve operation with flags.
427   444  
428   Resolves the host and service names into a list of endpoints. 445   Resolves the host and service names into a list of endpoints.
429   446  
430   This resolver must outlive the returned awaitable. 447   This resolver must outlive the returned awaitable.
431   448  
432   @param host A string identifying a location. 449   @param host A string identifying a location.
433   450  
434   @param service A string identifying the requested service. 451   @param service A string identifying the requested service.
435   452  
436   @param flags Flags controlling resolution behavior. 453   @param flags Flags controlling resolution behavior.
437   454  
438   @return An awaitable that completes with 455   @return An awaitable that completes with
439   `io_result<std::vector<endpoint>>`. 456   `io_result<std::vector<endpoint>>`.
440   */ 457   */
HITCBC 441   16 [[nodiscard]] auto resolve( 458   16 [[nodiscard]] auto resolve(
442   std::string_view host, std::string_view service, resolve_flags flags) 459   std::string_view host, std::string_view service, resolve_flags flags)
443   { 460   {
HITCBC 444   16 return resolve_awaitable(*this, host, service, flags); 461   16 return resolve_awaitable(*this, host, service, flags);
445   } 462   }
446   463  
447   /** Initiate an asynchronous reverse resolve operation. 464   /** Initiate an asynchronous reverse resolve operation.
448   465  
449   Resolves an endpoint into a hostname and service name using 466   Resolves an endpoint into a hostname and service name using
450   reverse DNS lookup (PTR record query). 467   reverse DNS lookup (PTR record query).
451   468  
452   This resolver must outlive the returned awaitable. 469   This resolver must outlive the returned awaitable.
453   470  
454   @param ep The endpoint to resolve. 471   @param ep The endpoint to resolve.
455   472  
456   @return An awaitable that completes with 473   @return An awaitable that completes with
457   `io_result<endpoint_name>`. 474   `io_result<endpoint_name>`.
458   475  
459   @par Example 476   @par Example
460   @par !example reverse_resolve 477   @par !example reverse_resolve
461   */ 478   */
HITCBC 462   11 [[nodiscard]] auto resolve(endpoint const& ep) 479   11 [[nodiscard]] auto resolve(endpoint const& ep)
463   { 480   {
HITCBC 464   11 return reverse_resolve_awaitable(*this, ep, reverse_flags::none); 481   11 return reverse_resolve_awaitable(*this, ep, reverse_flags::none);
465   } 482   }
466   483  
467   /** Initiate an asynchronous reverse resolve operation with flags. 484   /** Initiate an asynchronous reverse resolve operation with flags.
468   485  
469   Resolves an endpoint into a hostname and service name using 486   Resolves an endpoint into a hostname and service name using
470   reverse DNS lookup (PTR record query). 487   reverse DNS lookup (PTR record query).
471   488  
472   This resolver must outlive the returned awaitable. 489   This resolver must outlive the returned awaitable.
473   490  
474   @param ep The endpoint to resolve. 491   @param ep The endpoint to resolve.
475   492  
476   @param flags Flags controlling resolution behavior. See reverse_flags. 493   @param flags Flags controlling resolution behavior. See reverse_flags.
477   494  
478   @return An awaitable that completes with 495   @return An awaitable that completes with
479   `io_result<endpoint_name>`. 496   `io_result<endpoint_name>`.
480   */ 497   */
HITCBC 481   9 [[nodiscard]] auto resolve(endpoint const& ep, reverse_flags flags) 498   9 [[nodiscard]] auto resolve(endpoint const& ep, reverse_flags flags)
482   { 499   {
HITCBC 483   9 return reverse_resolve_awaitable(*this, ep, flags); 500   9 return reverse_resolve_awaitable(*this, ep, flags);
484   } 501   }
485   502  
486   /** Cancel any pending asynchronous operations. 503   /** Cancel any pending asynchronous operations.
487   504  
488 - Operations still in flight complete with `errc::operation_canceled`; 505 + A resolve transfers no bytes, so a cancellation always wins. An
489 - an operation whose result is already decided reports that result. 506 + operation reports `errc::operation_canceled` even when the lookup
490 - Check `ec == cond::canceled` for portable comparison. 507 + had already completed when the cancellation landed. Check
  508 + `ec == cond::canceled` for a portable comparison.
491   */ 509   */
492   void cancel() noexcept; 510   void cancel() noexcept;
493   511  
494   public: 512   public:
495 - /** Backend interface for DNS resolution operations. 513 + /** Define backend hooks for DNS resolution operations.
496   514  
497   Platform backends derive from this to implement forward and 515   Platform backends derive from this to implement forward and
498 - reverse DNS resolution via getaddrinfo/getnameinfo. 516 + reverse DNS resolution via `getaddrinfo`/`getnameinfo`.
499   */ 517   */
500   struct implementation : io_object::implementation 518   struct implementation : io_object::implementation
501   { 519   {
502 - /// Initiate an asynchronous forward DNS resolution. 520 + /** Initiate an asynchronous forward DNS resolution.
  521 +
  522 + @param h Coroutine handle to resume on completion.
  523 + @param ex Executor for dispatching the completion.
  524 + @param host The host name or address literal to resolve.
  525 + @param service The service name or port number.
  526 + @param flags Flags controlling the lookup.
  527 + @param token Stop token for cancellation.
  528 + @param ec Output error code.
  529 + @param results Output resolver results.
  530 +
  531 + @return Coroutine handle to resume immediately.
  532 + */
503   virtual std::coroutine_handle<> resolve( 533   virtual std::coroutine_handle<> resolve(
504 - std::coroutine_handle<>, 534 + std::coroutine_handle<> h,
505 - capy::executor_ref, 535 + capy::executor_ref ex,
506   std::string_view host, 536   std::string_view host,
507   std::string_view service, 537   std::string_view service,
508   resolve_flags flags, 538   resolve_flags flags,
509 - std::stop_token, 539 + std::stop_token token,
510 - std::error_code*, 540 + std::error_code* ec,
511 - std::vector<endpoint>*) = 0; 541 + std::vector<endpoint>* results) = 0;
512   542  
513 - /// Initiate an asynchronous reverse DNS resolution. 543 + /** Initiate an asynchronous reverse DNS resolution.
  544 +
  545 + @param h Coroutine handle to resume on completion.
  546 + @param ex Executor for dispatching the completion.
  547 + @param ep The endpoint to resolve.
  548 + @param flags Flags controlling the lookup.
  549 + @param token Stop token for cancellation.
  550 + @param ec Output error code.
  551 + @param result Output reverse-resolution result.
  552 +
  553 + @return Coroutine handle to resume immediately.
  554 + */
514   virtual std::coroutine_handle<> reverse_resolve( 555   virtual std::coroutine_handle<> reverse_resolve(
515 - std::coroutine_handle<>, 556 + std::coroutine_handle<> h,
516 - capy::executor_ref, 557 + capy::executor_ref ex,
517   endpoint const& ep, 558   endpoint const& ep,
518   reverse_flags flags, 559   reverse_flags flags,
519 - std::stop_token, 560 + std::stop_token token,
520 - std::error_code*, 561 + std::error_code* ec,
521 - endpoint_name*) = 0; 562 + endpoint_name* result) = 0;
522   563  
523   /// Cancel pending resolve operations. 564   /// Cancel pending resolve operations.
524   virtual void cancel() noexcept = 0; 565   virtual void cancel() noexcept = 0;
525   }; 566   };
526   567  
527   protected: 568   protected:
  569 + /** Adopt an existing handle.
  570 +
  571 + @param h The handle the resolver takes ownership of.
  572 + */
528   explicit resolver(handle h) noexcept : io_object(std::move(h)) {} 573   explicit resolver(handle h) noexcept : io_object(std::move(h)) {}
529   574  
530   private: 575   private:
HITCBC 531   59 inline implementation& get() const noexcept 576   59 inline implementation& get() const noexcept
532   { 577   {
HITCBC 533   59 return *static_cast<implementation*>(h_.get()); 578   59 return *static_cast<implementation*>(h_.get());
534   } 579   }
535   }; 580   };
536   581  
537   } // namespace boost::corosio 582   } // namespace boost::corosio
538   583  
539   #endif 584   #endif