text: /*
   *
   * Copyright 2015 gRPC authors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *
   */
  
  #ifndef GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_CLIENT_CHANNEL_H
  #define GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_CLIENT_CHANNEL_H
  
  #include <grpc/support/port_platform.h>
  
  #include "src/core/ext/filters/client_channel/client_channel_channelz.h"
  #include "src/core/ext/filters/client_channel/client_channel_factory.h"
  #include "src/core/ext/filters/client_channel/resolver.h"
  #include "src/core/lib/channel/channel_stack.h"
  
  extern grpc_core::TraceFlag grpc_client_channel_trace;
  
  // Channel arg key for server URI string.
  #define GRPC_ARG_SERVER_URI "grpc.server_uri"
  
  /* A client channel is a channel that begins disconnected, and can connect
     to some endpoint on demand. If that endpoint disconnects, it will be
     connected to again later.
  
     Calls on a disconnected client channel are queued until a connection is
     established. */
  
  extern const grpc_channel_filter grpc_client_channel_filter;
  
  grpc_connectivity_state grpc_client_channel_check_connectivity_state(
      grpc_channel_element* elem, int try_to_connect);
  
  int grpc_client_channel_num_external_connectivity_watchers(
      grpc_channel_element* elem);
  
  // Starts a one-time connectivity state watch.  When the channel's state
  // becomes different from *state, sets *state to the new state and
  // schedules on_complete.  The watcher_timer_init callback is invoked as
  // soon as the watch is actually started (i.e., after hopping into the
  // client channel combiner).  I/O will be serviced via pollent.
  //
  // This is intended to be used when starting a watch from outside of C-core
  // via grpc_channel_watch_connectivity_state().  It should not be used
  // by other callers.
  void grpc_client_channel_watch_connectivity_state(
      grpc_channel_element* elem, grpc_polling_entity pollent,
      grpc_connectivity_state* state, grpc_closure* on_complete,
      grpc_closure* watcher_timer_init);
  
  // Starts and stops a connectivity watch.  The watcher will be initially
  // notified as soon as the state changes from initial_state and then on
  // every subsequent state change until either the watch is stopped or
  // it is notified that the state has changed to SHUTDOWN.
  //
  // This is intended to be used when starting watches from code inside of
  // C-core (e.g., for a nested control plane channel for things like xds).
  void grpc_client_channel_start_connectivity_watch(
      grpc_channel_element* elem, grpc_connectivity_state initial_state,
      grpc_core::OrphanablePtr<grpc_core::AsyncConnectivityStateWatcherInterface>
          watcher);
  void grpc_client_channel_stop_connectivity_watch(
      grpc_channel_element* elem,
      grpc_core::AsyncConnectivityStateWatcherInterface* watcher);
  
  /* Debug helper: pull the subchannel call from a call stack element */
  grpc_core::RefCountedPtr<grpc_core::SubchannelCall>
  grpc_client_channel_get_subchannel_call(grpc_call_element* elem);
  
  #endif  // GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_CLIENT_CHANNEL_H
  