ceph/src/boost/boost/asio/strand.hpp

   1 //
   2 // strand.hpp
   3 // ~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2020 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_STRAND_HPP
  12 #define BOOST_ASIO_STRAND_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 #include <boost/asio/detail/strand_executor_service.hpp>
  20 #include <boost/asio/detail/type_traits.hpp>
  21
  22 #include <boost/asio/detail/push_options.hpp>
  23
  24 namespace boost {
  25 namespace asio {
  26
  27 /// Provides serialised function invocation for any executor type.
  28 template <typename Executor>
  29 class strand
  30 {
  31 public:
  32   /// The type of the underlying executor.
  33   typedef Executor inner_executor_type;
  34
  35   /// Default constructor.
  36   /**
  37    * This constructor is only valid if the underlying executor type is default
  38    * constructible.
  39    */
  40   strand()
  41     : executor_(),
  42       impl_(use_service<detail::strand_executor_service>(
  43             executor_.context()).create_implementation())
  44   {
  45   }
  46
  47   /// Construct a strand for the specified executor.
  48   explicit strand(const Executor& e)
  49     : executor_(e),
  50       impl_(use_service<detail::strand_executor_service>(
  51             executor_.context()).create_implementation())
  52   {
  53   }
  54
  55   /// Copy constructor.
  56   strand(const strand& other) BOOST_ASIO_NOEXCEPT
  57     : executor_(other.executor_),
  58       impl_(other.impl_)
  59   {
  60   }
  61
  62   /// Converting constructor.
  63   /**
  64    * This constructor is only valid if the @c OtherExecutor type is convertible
  65    * to @c Executor.
  66    */
  67   template <class OtherExecutor>
  68   strand(
  69       const strand<OtherExecutor>& other) BOOST_ASIO_NOEXCEPT
  70     : executor_(other.executor_),
  71       impl_(other.impl_)
  72   {
  73   }
  74
  75   /// Assignment operator.
  76   strand& operator=(const strand& other) BOOST_ASIO_NOEXCEPT
  77   {
  78     executor_ = other.executor_;
  79     impl_ = other.impl_;
  80     return *this;
  81   }
  82
  83   /// Converting assignment operator.
  84   /**
  85    * This assignment operator is only valid if the @c OtherExecutor type is
  86    * convertible to @c Executor.
  87    */
  88   template <class OtherExecutor>
  89   strand& operator=(
  90       const strand<OtherExecutor>& other) BOOST_ASIO_NOEXCEPT
  91   {
  92     executor_ = other.executor_;
  93     impl_ = other.impl_;
  94     return *this;
  95   }
  96
  97 #if defined(BOOST_ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
  98   /// Move constructor.
  99   strand(strand&& other) BOOST_ASIO_NOEXCEPT
 100     : executor_(BOOST_ASIO_MOVE_CAST(Executor)(other.executor_)),
 101       impl_(BOOST_ASIO_MOVE_CAST(implementation_type)(other.impl_))
 102   {
 103   }
 104
 105   /// Converting move constructor.
 106   /**
 107    * This constructor is only valid if the @c OtherExecutor type is convertible
 108    * to @c Executor.
 109    */
 110   template <class OtherExecutor>
 111   strand(strand<OtherExecutor>&& other) BOOST_ASIO_NOEXCEPT
 112     : executor_(BOOST_ASIO_MOVE_CAST(OtherExecutor)(other.executor_)),
 113       impl_(BOOST_ASIO_MOVE_CAST(implementation_type)(other.impl_))
 114   {
 115   }
 116
 117   /// Move assignment operator.
 118   strand& operator=(strand&& other) BOOST_ASIO_NOEXCEPT
 119   {
 120     executor_ = BOOST_ASIO_MOVE_CAST(Executor)(other.executor_);
 121     impl_ = BOOST_ASIO_MOVE_CAST(implementation_type)(other.impl_);
 122     return *this;
 123   }
 124
 125   /// Converting move assignment operator.
 126   /**
 127    * This assignment operator is only valid if the @c OtherExecutor type is
 128    * convertible to @c Executor.
 129    */
 130   template <class OtherExecutor>
 131   strand& operator=(strand<OtherExecutor>&& other) BOOST_ASIO_NOEXCEPT
 132   {
 133     executor_ = BOOST_ASIO_MOVE_CAST(OtherExecutor)(other.executor_);
 134     impl_ = BOOST_ASIO_MOVE_CAST(implementation_type)(other.impl_);
 135     return *this;
 136   }
 137 #endif // defined(BOOST_ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
 138
 139   /// Destructor.
 140   ~strand()
 141   {
 142   }
 143
 144   /// Obtain the underlying executor.
 145   inner_executor_type get_inner_executor() const BOOST_ASIO_NOEXCEPT
 146   {
 147     return executor_;
 148   }
 149
 150   /// Obtain the underlying execution context.
 151   execution_context& context() const BOOST_ASIO_NOEXCEPT
 152   {
 153     return executor_.context();
 154   }
 155
 156   /// Inform the strand that it has some outstanding work to do.
 157   /**
 158    * The strand delegates this call to its underlying executor.
 159    */
 160   void on_work_started() const BOOST_ASIO_NOEXCEPT
 161   {
 162     executor_.on_work_started();
 163   }
 164
 165   /// Inform the strand that some work is no longer outstanding.
 166   /**
 167    * The strand delegates this call to its underlying executor.
 168    */
 169   void on_work_finished() const BOOST_ASIO_NOEXCEPT
 170   {
 171     executor_.on_work_finished();
 172   }
 173
 174   /// Request the strand to invoke the given function object.
 175   /**
 176    * This function is used to ask the strand to execute the given function
 177    * object on its underlying executor. The function object will be executed
 178    * inside this function if the strand is not otherwise busy and if the
 179    * underlying executor's @c dispatch() function is also able to execute the
 180    * function before returning.
 181    *
 182    * @param f The function object to be called. The executor will make
 183    * a copy of the handler object as required. The function signature of the
 184    * function object must be: @code void function(); @endcode
 185    *
 186    * @param a An allocator that may be used by the executor to allocate the
 187    * internal storage needed for function invocation.
 188    */
 189   template <typename Function, typename Allocator>
 190   void dispatch(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
 191   {
 192     detail::strand_executor_service::dispatch(impl_,
 193         executor_, BOOST_ASIO_MOVE_CAST(Function)(f), a);
 194   }
 195
 196   /// Request the strand to invoke the given function object.
 197   /**
 198    * This function is used to ask the executor to execute the given function
 199    * object. The function object will never be executed inside this function.
 200    * Instead, it will be scheduled by the underlying executor's defer function.
 201    *
 202    * @param f The function object to be called. The executor will make
 203    * a copy of the handler object as required. The function signature of the
 204    * function object must be: @code void function(); @endcode
 205    *
 206    * @param a An allocator that may be used by the executor to allocate the
 207    * internal storage needed for function invocation.
 208    */
 209   template <typename Function, typename Allocator>
 210   void post(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
 211   {
 212     detail::strand_executor_service::post(impl_,
 213         executor_, BOOST_ASIO_MOVE_CAST(Function)(f), a);
 214   }
 215
 216   /// Request the strand to invoke the given function object.
 217   /**
 218    * This function is used to ask the executor to execute the given function
 219    * object. The function object will never be executed inside this function.
 220    * Instead, it will be scheduled by the underlying executor's defer function.
 221    *
 222    * @param f The function object to be called. The executor will make
 223    * a copy of the handler object as required. The function signature of the
 224    * function object must be: @code void function(); @endcode
 225    *
 226    * @param a An allocator that may be used by the executor to allocate the
 227    * internal storage needed for function invocation.
 228    */
 229   template <typename Function, typename Allocator>
 230   void defer(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
 231   {
 232     detail::strand_executor_service::defer(impl_,
 233         executor_, BOOST_ASIO_MOVE_CAST(Function)(f), a);
 234   }
 235
 236   /// Determine whether the strand is running in the current thread.
 237   /**
 238    * @return @c true if the current thread is executing a function that was
 239    * submitted to the strand using post(), dispatch() or defer(). Otherwise
 240    * returns @c false.
 241    */
 242   bool running_in_this_thread() const BOOST_ASIO_NOEXCEPT
 243   {
 244     return detail::strand_executor_service::running_in_this_thread(impl_);
 245   }
 246
 247   /// Compare two strands for equality.
 248   /**
 249    * Two strands are equal if they refer to the same ordered, non-concurrent
 250    * state.
 251    */
 252   friend bool operator==(const strand& a, const strand& b) BOOST_ASIO_NOEXCEPT
 253   {
 254     return a.impl_ == b.impl_;
 255   }
 256
 257   /// Compare two strands for inequality.
 258   /**
 259    * Two strands are equal if they refer to the same ordered, non-concurrent
 260    * state.
 261    */
 262   friend bool operator!=(const strand& a, const strand& b) BOOST_ASIO_NOEXCEPT
 263   {
 264     return a.impl_ != b.impl_;
 265   }
 266
 267 #if defined(GENERATING_DOCUMENTATION)
 268 private:
 269 #endif // defined(GENERATING_DOCUMENTATION)
 270   Executor executor_;
 271   typedef detail::strand_executor_service::implementation_type
 272     implementation_type;
 273   implementation_type impl_;
 274 };
 275
 276 /** @defgroup make_strand boost::asio::make_strand
 277  *
 278  * @brief The boost::asio::make_strand function creates a @ref strand object for
 279  * an executor or execution context.
 280  */
 281 /*@{*/
 282
 283 /// Create a @ref strand object for an executor.
 284 template <typename Executor>
 285 inline strand<Executor> make_strand(const Executor& ex,
 286     typename enable_if<is_executor<Executor>::value>::type* = 0)
 287 {
 288   return strand<Executor>(ex);
 289 }
 290
 291 /// Create a @ref strand object for an execution context.
 292 template <typename ExecutionContext>
 293 inline strand<typename ExecutionContext::executor_type>
 294 make_strand(ExecutionContext& ctx,
 295     typename enable_if<
 296       is_convertible<ExecutionContext&, execution_context&>::value>::type* = 0)
 297 {
 298   return strand<typename ExecutionContext::executor_type>(ctx.get_executor());
 299 }
 300
 301 /*@}*/
 302
 303 } // namespace asio
 304 } // namespace boost
 305
 306 #include <boost/asio/detail/pop_options.hpp>
 307
 308 // If both io_context.hpp and strand.hpp have been included, automatically
 309 // include the header file needed for the io_context::strand class.
 310 #if !defined(BOOST_ASIO_NO_EXTENSIONS)
 311 # if defined(BOOST_ASIO_IO_CONTEXT_HPP)
 312 #  include <boost/asio/io_context_strand.hpp>
 313 # endif // defined(BOOST_ASIO_IO_CONTEXT_HPP)
 314 #endif // !defined(BOOST_ASIO_NO_EXTENSIONS)
 315
 316 #endif // BOOST_ASIO_STRAND_HPP