/*
 * Copyright 2017 Facebook, Inc.
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.
 */
#pragma once

#include <functional>
#include <event.h>  // libevent

namespace folly {

# if LIBEVENT_VERSION_NUMBER <= 0x02010101
#   define FOLLY_LIBEVENT_COMPAT_PLUCK(name) ev_##name
# else
#   define FOLLY_LIBEVENT_COMPAT_PLUCK(name) ev_evcallback.evcb_##name
# endif
# define FOLLY_LIBEVENT_DEF_ACCESSORS(name) \
    inline auto event_ref_##name(struct event* ev) -> \
      decltype(std::ref(ev->FOLLY_LIBEVENT_COMPAT_PLUCK(name))) \
      { return std::ref(ev->FOLLY_LIBEVENT_COMPAT_PLUCK(name)); } \
    inline auto event_ref_##name(struct event const* ev) -> \
      decltype(std::cref(ev->FOLLY_LIBEVENT_COMPAT_PLUCK(name))) \
      { return std::cref(ev->FOLLY_LIBEVENT_COMPAT_PLUCK(name)); } \
    //

FOLLY_LIBEVENT_DEF_ACCESSORS(flags)

# undef FOLLY_LIBEVENT_COMPAT_PLUCK
# undef FOLLY_LIBEVENT_DEF_ACCESSORS

/**
 * low-level libevent utility functions
 */
class EventUtil {
 public:
  static bool isEventRegistered(const struct event* ev) {
    // If any of these flags are set, the event is registered.
    enum {
      EVLIST_REGISTERED = (EVLIST_INSERTED | EVLIST_ACTIVE |
                           EVLIST_TIMEOUT | EVLIST_SIGNAL)
    };
    return (event_ref_flags(ev) & EVLIST_REGISTERED);
  }
};

} // folly
