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       1              : //
       2              : // Copyright (c) 2026 Steve Gerbino
       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/corosio
       8              : //
       9              : 
      10              : #ifndef BOOST_COROSIO_DETAIL_POSIX_RESOLVER_SERVICE_HPP
      11              : #define BOOST_COROSIO_DETAIL_POSIX_RESOLVER_SERVICE_HPP
      12              : 
      13              : #include <boost/corosio/detail/platform.hpp>
      14              : 
      15              : #if BOOST_COROSIO_POSIX
      16              : 
      17              : #include <boost/corosio/detail/config.hpp>
      18              : #include <boost/corosio/resolver.hpp>
      19              : #include <boost/capy/ex/execution_context.hpp>
      20              : 
      21              : /*
      22              :     POSIX Resolver Service
      23              :     ======================
      24              : 
      25              :     POSIX getaddrinfo() is a blocking call that cannot be monitored with
      26              :     epoll/kqueue/io_uring. We use a worker thread approach: each resolution
      27              :     spawns a dedicated thread that runs the blocking call and posts completion
      28              :     back to the scheduler.
      29              : 
      30              :     This follows the timer_service pattern:
      31              :     - posix_resolver_service is an abstract base class (no scheduler dependency)
      32              :     - posix_resolver_service_impl is the concrete implementation
      33              :     - get_resolver_service(ctx, sched) creates the service with scheduler ref
      34              : 
      35              :     Thread-per-resolution Design
      36              :     ----------------------------
      37              :     Simple, no thread pool complexity. DNS lookups are infrequent enough that
      38              :     thread creation overhead is acceptable. Detached threads self-manage;
      39              :     shared_ptr capture keeps impl alive until completion.
      40              : 
      41              :     Cancellation
      42              :     ------------
      43              :     getaddrinfo() cannot be interrupted mid-call. We use an atomic flag to
      44              :     indicate cancellation was requested. The worker thread checks this flag
      45              :     after getaddrinfo() returns and reports the appropriate error.
      46              : */
      47              : 
      48              : namespace boost::corosio::detail {
      49              : 
      50              : struct scheduler;
      51              : 
      52              : //------------------------------------------------------------------------------
      53              : 
      54              : /** Abstract resolver service for POSIX backends.
      55              : 
      56              :     This is the base class that defines the interface. The concrete
      57              :     implementation (posix_resolver_service_impl) is created via
      58              :     get_resolver_service() which passes the scheduler reference.
      59              : */
      60              : class posix_resolver_service : public capy::execution_context::service
      61              : {
      62              : public:
      63              :     /** Create a new resolver implementation. */
      64              :     virtual resolver::resolver_impl& create_impl() = 0;
      65              : 
      66              : protected:
      67          304 :     posix_resolver_service() = default;
      68              : };
      69              : 
      70              : //------------------------------------------------------------------------------
      71              : 
      72              : /** Get or create the resolver service for the given context.
      73              : 
      74              :     This function is called by the concrete scheduler during initialization
      75              :     to create the resolver service with a reference to itself.
      76              : 
      77              :     @param ctx Reference to the owning execution_context.
      78              :     @param sched Reference to the scheduler for posting completions.
      79              :     @return Reference to the resolver service.
      80              : */
      81              : posix_resolver_service&
      82              : get_resolver_service(capy::execution_context& ctx, scheduler& sched);
      83              : 
      84              : } // namespace boost::corosio::detail
      85              : 
      86              : #endif // BOOST_COROSIO_POSIX
      87              : 
      88              : #endif // BOOST_COROSIO_DETAIL_POSIX_RESOLVER_SERVICE_HPP