endpoints_resolver.hpp

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#ifndef ENDPOINTS_RESOLVER_HPP_INCLUDED
#define ENDPOINTS_RESOLVER_HPP_INCLUDED
 
#include "asio/ip/basic_resolver.hpp"
#include "asio/io_context.hpp"
 
#include <string_view>
#include <string>
#include <utility> // std::move, std::forward
 
#include "nonstd/expected.hpp"
 
namespace chops {
namespace net {
 
template <typename Protocol>
class endpoints_resolver {
private:
  asio::ip::basic_resolver<Protocol>  m_resolver;
 
public:
 
  explicit endpoints_resolver(asio::io_context& ioc) : m_resolver(ioc) { }
 
  template <typename F>
  void make_endpoints(bool local, std::string_view host_or_intf_name, 
                      std::string_view service_or_port, F&& func) {
 
    // Note - std::move used instead of std::forward since an explicit move or copy
    // is needed to prevent worry about dangling references
    if (local) {
      m_resolver.async_resolve(host_or_intf_name, service_or_port, 
                        asio::ip::resolver_base::flags(asio::ip::resolver_base::passive | 
                                                 asio::ip::resolver_base::address_configured),
                        std::move(func));
    }
    else {
      m_resolver.async_resolve(host_or_intf_name, service_or_port,
                        std::move(func));
    }
    return;
  }
 
  void cancel() {
    m_resolver.cancel();
  }
 
  auto make_endpoints(bool local, std::string_view host_or_intf_name, std::string_view service_or_port) ->
      nonstd::expected<asio::ip::basic_resolver_results<Protocol>, std::error_code> {
 
    std::error_code ec;
    auto res = m_resolver.resolve(host_or_intf_name, service_or_port,
          (local ? asio::ip::resolver_base::flags(asio::ip::resolver_base::passive | 
                                                  asio::ip::resolver_base::address_configured) :
                   asio::ip::resolver_base::flags()), ec);
    if (ec) {
      return nonstd::make_unexpected(ec);
    }
    return res;
 
  }
 
};
 
}  // end net namespace
}  // end chops namespace
 
#endif