ceph/src/boost/boost/asio/detail/std_event.hpp

   1 //
   2 // detail/std_event.hpp
   3 // ~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
   6 //
   7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   9 //
  10
  11 #ifndef BOOST_ASIO_DETAIL_STD_EVENT_HPP
  12 #define BOOST_ASIO_DETAIL_STD_EVENT_HPP
  13
  14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  15 # pragma once
  16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  17
  18 #include <boost/asio/detail/config.hpp>
  19
  20 #if defined(BOOST_ASIO_HAS_STD_MUTEX_AND_CONDVAR)
  21
  22 #include <chrono>
  23 #include <condition_variable>
  24 #include <boost/asio/detail/assert.hpp>
  25 #include <boost/asio/detail/noncopyable.hpp>
  26
  27 #include <boost/asio/detail/push_options.hpp>
  28
  29 namespace boost {
  30 namespace asio {
  31 namespace detail {
  32
  33 class std_event
  34   : private noncopyable
  35 {
  36 public:
  37   // Constructor.
  38   std_event()
  39     : state_(0)
  40   {
  41   }
  42
  43   // Destructor.
  44   ~std_event()
  45   {
  46   }
  47
  48   // Signal the event. (Retained for backward compatibility.)
  49   template <typename Lock>
  50   void signal(Lock& lock)
  51   {
  52     this->signal_all(lock);
  53   }
  54
  55   // Signal all waiters.
  56   template <typename Lock>
  57   void signal_all(Lock& lock)
  58   {
  59     BOOST_ASIO_ASSERT(lock.locked());
  60     (void)lock;
  61     state_ |= 1;
  62     cond_.notify_all();
  63   }
  64
  65   // Unlock the mutex and signal one waiter.
  66   template <typename Lock>
  67   void unlock_and_signal_one(Lock& lock)
  68   {
  69     BOOST_ASIO_ASSERT(lock.locked());
  70     state_ |= 1;
  71     bool have_waiters = (state_ > 1);
  72     lock.unlock();
  73     if (have_waiters)
  74       cond_.notify_one();
  75   }
  76
  77   // If there's a waiter, unlock the mutex and signal it.
  78   template <typename Lock>
  79   bool maybe_unlock_and_signal_one(Lock& lock)
  80   {
  81     BOOST_ASIO_ASSERT(lock.locked());
  82     state_ |= 1;
  83     if (state_ > 1)
  84     {
  85       lock.unlock();
  86       cond_.notify_one();
  87       return true;
  88     }
  89     return false;
  90   }
  91
  92   // Reset the event.
  93   template <typename Lock>
  94   void clear(Lock& lock)
  95   {
  96     BOOST_ASIO_ASSERT(lock.locked());
  97     (void)lock;
  98     state_ &= ~std::size_t(1);
  99   }
 100
 101   // Wait for the event to become signalled.
 102   template <typename Lock>
 103   void wait(Lock& lock)
 104   {
 105     BOOST_ASIO_ASSERT(lock.locked());
 106     unique_lock_adapter u_lock(lock);
 107     while ((state_ & 1) == 0)
 108     {
 109       waiter w(state_);
 110       cond_.wait(u_lock.unique_lock_);
 111     }
 112   }
 113
 114   // Timed wait for the event to become signalled.
 115   template <typename Lock>
 116   bool wait_for_usec(Lock& lock, long usec)
 117   {
 118     BOOST_ASIO_ASSERT(lock.locked());
 119     unique_lock_adapter u_lock(lock);
 120     if ((state_ & 1) == 0)
 121     {
 122       waiter w(state_);
 123       cond_.wait_for(u_lock.unique_lock_, std::chrono::microseconds(usec));
 124     }
 125     return (state_ & 1) != 0;
 126   }
 127
 128 private:
 129   // Helper class to temporarily adapt a scoped_lock into a unique_lock so that
 130   // it can be passed to std::condition_variable::wait().
 131   struct unique_lock_adapter
 132   {
 133     template <typename Lock>
 134     explicit unique_lock_adapter(Lock& lock)
 135       : unique_lock_(lock.mutex().mutex_, std::adopt_lock)
 136     {
 137     }
 138
 139     ~unique_lock_adapter()
 140     {
 141       unique_lock_.release();
 142     }
 143
 144     std::unique_lock<std::mutex> unique_lock_;
 145   };
 146
 147   // Helper to increment and decrement the state to track outstanding waiters.
 148   class waiter
 149   {
 150   public:
 151     explicit waiter(std::size_t& state)
 152       : state_(state)
 153     {
 154       state_ += 2;
 155     }
 156
 157     ~waiter()
 158     {
 159       state_ -= 2;
 160     }
 161
 162   private:
 163     std::size_t& state_;
 164   };
 165
 166   std::condition_variable cond_;
 167   std::size_t state_;
 168 };
 169
 170 } // namespace detail
 171 } // namespace asio
 172 } // namespace boost
 173
 174 #include <boost/asio/detail/pop_options.hpp>
 175
 176 #endif // defined(BOOST_ASIO_HAS_STD_MUTEX_AND_CONDVAR)
 177
 178 #endif // BOOST_ASIO_DETAIL_STD_EVENT_HPP