text: /*
   *
   * Copyright 2015, Google Inc.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   *     * Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *     * Redistributions in binary form must reproduce the above
   * copyright notice, this list of conditions and the following disclaimer
   * in the documentation and/or other materials provided with the
   * distribution.
   *     * Neither the name of Google Inc. nor the names of its
   * contributors may be used to endorse or promote products derived from
   * this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   */
  
  #ifndef GRPC_CORE_LIB_TRANSPORT_CONNECTIVITY_STATE_H
  #define GRPC_CORE_LIB_TRANSPORT_CONNECTIVITY_STATE_H
  
  #include <grpc/grpc.h>
  #include "src/core/lib/debug/trace.h"
  #include "src/core/lib/iomgr/exec_ctx.h"
  
  typedef struct grpc_connectivity_state_watcher {
    /** we keep watchers in a linked list */
    struct grpc_connectivity_state_watcher *next;
    /** closure to notify on change */
    grpc_closure *notify;
    /** the current state as believed by the watcher */
    grpc_connectivity_state *current;
  } grpc_connectivity_state_watcher;
  
  typedef struct {
    /** current grpc_connectivity_state */
    gpr_atm current_state_atm;
    /** error associated with state */
    grpc_error *current_error;
    /** all our watchers */
    grpc_connectivity_state_watcher *watchers;
    /** a name to help debugging */
    char *name;
  } grpc_connectivity_state_tracker;
  
  extern grpc_tracer_flag grpc_connectivity_state_trace;
  
  /** enum --> string conversion */
  const char *grpc_connectivity_state_name(grpc_connectivity_state state);
  
  void grpc_connectivity_state_init(grpc_connectivity_state_tracker *tracker,
                                    grpc_connectivity_state init_state,
                                    const char *name);
  void grpc_connectivity_state_destroy(grpc_exec_ctx *exec_ctx,
                                       grpc_connectivity_state_tracker *tracker);
  
  /** Set connectivity state; not thread safe; access must be serialized with an
   *  external lock */
  void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
                                   grpc_connectivity_state_tracker *tracker,
                                   grpc_connectivity_state state,
                                   grpc_error *associated_error,
                                   const char *reason);
  
  /** Return true if this connectivity state has watchers.
      Access must be serialized with an external lock. */
  bool grpc_connectivity_state_has_watchers(
      grpc_connectivity_state_tracker *tracker);
  
  /** Return the last seen connectivity state. No need to synchronize access. */
  grpc_connectivity_state grpc_connectivity_state_check(
      grpc_connectivity_state_tracker *tracker);
  
  /** Return the last seen connectivity state, and the associated error.
      Access must be serialized with an external lock. */
  grpc_connectivity_state grpc_connectivity_state_get(
      grpc_connectivity_state_tracker *tracker, grpc_error **error);
  
  /** Return 1 if the channel should start connecting, 0 otherwise.
      If current==NULL cancel notify if it is already queued (success==0 in that
      case).
      Access must be serialized with an external lock. */
  bool grpc_connectivity_state_notify_on_state_change(
      grpc_exec_ctx *exec_ctx, grpc_connectivity_state_tracker *tracker,
      grpc_connectivity_state *current, grpc_closure *notify);
  
  #endif /* GRPC_CORE_LIB_TRANSPORT_CONNECTIVITY_STATE_H */
  