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include/asio/detail/resolve_query_op.hpp

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+//
+// detail/resolve_query_op.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2025 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef ASIO_DETAIL_RESOLVE_QUERY_OP_HPP
+#define ASIO_DETAIL_RESOLVE_QUERY_OP_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+#include "asio/detail/bind_handler.hpp"
+#include "asio/detail/fenced_block.hpp"
+#include "asio/detail/handler_alloc_helpers.hpp"
+#include "asio/detail/handler_work.hpp"
+#include "asio/detail/memory.hpp"
+#include "asio/detail/resolve_op.hpp"
+#include "asio/detail/socket_ops.hpp"
+#include "asio/error.hpp"
+#include "asio/ip/basic_resolver_query.hpp"
+#include "asio/ip/basic_resolver_results.hpp"
+
+#if defined(ASIO_HAS_IOCP)
+# include "asio/detail/win_iocp_io_context.hpp"
+#else // defined(ASIO_HAS_IOCP)
+# include "asio/detail/scheduler.hpp"
+#endif // defined(ASIO_HAS_IOCP)
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+template <typename Protocol, typename Handler, typename IoExecutor>
+class resolve_query_op : public resolve_op
+{
+public:
+  ASIO_DEFINE_HANDLER_PTR(resolve_query_op);
+
+  typedef asio::ip::basic_resolver_query<Protocol> query_type;
+  typedef asio::ip::basic_resolver_results<Protocol> results_type;
+
+#if defined(ASIO_HAS_IOCP)
+  typedef class win_iocp_io_context scheduler_impl;
+#else
+  typedef class scheduler scheduler_impl;
+#endif
+
+  resolve_query_op(socket_ops::weak_cancel_token_type cancel_token,
+      const query_type& qry, scheduler_impl& sched,
+      Handler& handler, const IoExecutor& io_ex)
+    : resolve_op(&resolve_query_op::do_complete),
+      cancel_token_(cancel_token),
+      query_(qry),
+      scheduler_(sched),
+      handler_(static_cast<Handler&&>(handler)),
+      work_(handler_, io_ex),
+      addrinfo_(0)
+  {
+  }
+
+  ~resolve_query_op()
+  {
+    if (addrinfo_)
+      socket_ops::freeaddrinfo(addrinfo_);
+  }
+
+  static void do_complete(void* owner, operation* base,
+      const asio::error_code& /*ec*/,
+      std::size_t /*bytes_transferred*/)
+  {
+    // Take ownership of the operation object.
+    ASIO_ASSUME(base != 0);
+    resolve_query_op* o(static_cast<resolve_query_op*>(base));
+    ptr p = { asio::detail::addressof(o->handler_), o, o };
+
+    if (owner && owner != &o->scheduler_)
+    {
+      // The operation is being run on the worker io_context. Time to perform
+      // the resolver operation.
+
+      // Perform the blocking host resolution operation.
+      socket_ops::background_getaddrinfo(o->cancel_token_,
+          o->query_.host_name().c_str(), o->query_.service_name().c_str(),
+          o->query_.hints(), &o->addrinfo_, o->ec_);
+
+      // Pass operation back to main io_context for completion.
+      o->scheduler_.post_deferred_completion(o);
+      p.v = p.p = 0;
+    }
+    else
+    {
+      // The operation has been returned to the main io_context. The completion
+      // handler is ready to be delivered.
+
+      ASIO_HANDLER_COMPLETION((*o));
+
+      // Take ownership of the operation's outstanding work.
+      handler_work<Handler, IoExecutor> w(
+          static_cast<handler_work<Handler, IoExecutor>&&>(
+            o->work_));
+
+      // Make a copy of the handler so that the memory can be deallocated
+      // before the upcall is made. Even if we're not about to make an upcall,
+      // a sub-object of the handler may be the true owner of the memory
+      // associated with the handler. Consequently, a local copy of the handler
+      // is required to ensure that any owning sub-object remains valid until
+      // after we have deallocated the memory here.
+      detail::binder2<Handler, asio::error_code, results_type>
+        handler(o->handler_, o->ec_, results_type());
+      p.h = asio::detail::addressof(handler.handler_);
+      if (o->addrinfo_)
+      {
+        handler.arg2_ = results_type::create(o->addrinfo_,
+            o->query_.host_name(), o->query_.service_name());
+      }
+      p.reset();
+
+      if (owner)
+      {
+        fenced_block b(fenced_block::half);
+        ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, "..."));
+        w.complete(handler, handler.handler_);
+        ASIO_HANDLER_INVOCATION_END;
+      }
+    }
+  }
+
+private:
+  socket_ops::weak_cancel_token_type cancel_token_;
+  query_type query_;
+  scheduler_impl& scheduler_;
+  Handler handler_;
+  handler_work<Handler, IoExecutor> work_;
+  asio::detail::addrinfo_type* addrinfo_;
+};
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_DETAIL_RESOLVE_QUERY_OP_HPP