text: //
  // strand.cpp
  // ~~~~~~~~~~
  //
  // Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  //
  // Distributed under the Boost Software License, Version 1.0. (See accompanying
  // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  
  // Disable autolinking for unit tests.
  #if !defined(BOOST_ALL_NO_LIB)
  #define BOOST_ALL_NO_LIB 1
  #endif // !defined(BOOST_ALL_NO_LIB)
  
  // Test that header file is self-contained.
  #include <boost/asio/strand.hpp>
  
  #include <sstream>
  #include <boost/asio/io_context.hpp>
  #include <boost/asio/dispatch.hpp>
  #include <boost/asio/post.hpp>
  #include <boost/asio/detail/thread.hpp>
  #include "unit_test.hpp"
  
  #if defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
  # include <boost/asio/deadline_timer.hpp>
  #else // defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
  # include <boost/asio/steady_timer.hpp>
  #endif // defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
  
  #if defined(BOOST_ASIO_HAS_BOOST_BIND)
  # include <boost/bind.hpp>
  #else // defined(BOOST_ASIO_HAS_BOOST_BIND)
  # include <functional>
  #endif // defined(BOOST_ASIO_HAS_BOOST_BIND)
  
  using namespace boost::asio;
  
  #if defined(BOOST_ASIO_HAS_BOOST_BIND)
  namespace bindns = boost;
  #else // defined(BOOST_ASIO_HAS_BOOST_BIND)
  namespace bindns = std;
  #endif
  
  #if defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
  typedef deadline_timer timer;
  namespace chronons = boost::posix_time;
  #elif defined(BOOST_ASIO_HAS_CHRONO)
  typedef steady_timer timer;
  namespace chronons = boost::asio::chrono;
  #endif // defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
  
  void increment(int* count)
  {
    ++(*count);
  }
  
  void increment_without_lock(io_context::strand* s, int* count)
  {
    BOOST_ASIO_CHECK(!s->running_in_this_thread());
  
    int original_count = *count;
  
    dispatch(*s, bindns::bind(increment, count));
  
    // No other functions are currently executing through the locking dispatcher,
    // so the previous call to dispatch should have successfully nested.
    BOOST_ASIO_CHECK(*count == original_count + 1);
  }
  
  void increment_with_lock(io_context::strand* s, int* count)
  {
    BOOST_ASIO_CHECK(s->running_in_this_thread());
  
    int original_count = *count;
  
    dispatch(*s, bindns::bind(increment, count));
  
    // The current function already holds the strand's lock, so the
    // previous call to dispatch should have successfully nested.
    BOOST_ASIO_CHECK(*count == original_count + 1);
  }
  
  void sleep_increment(io_context* ioc, int* count)
  {
    timer t(*ioc, chronons::seconds(2));
    t.wait();
  
    ++(*count);
  }
  
  void increment_by_a(int* count, int a)
  {
    (*count) += a;
  }
  
  void increment_by_a_b(int* count, int a, int b)
  {
    (*count) += a + b;
  }
  
  void increment_by_a_b_c(int* count, int a, int b, int c)
  {
    (*count) += a + b + c;
  }
  
  void increment_by_a_b_c_d(int* count, int a, int b, int c, int d)
  {
    (*count) += a + b + c + d;
  }
  
  void start_sleep_increments(io_context* ioc, io_context::strand* s, int* count)
  {
    // Give all threads a chance to start.
    timer t(*ioc, chronons::seconds(2));
    t.wait();
  
    // Start three increments.
    post(*s, bindns::bind(sleep_increment, ioc, count));
    post(*s, bindns::bind(sleep_increment, ioc, count));
    post(*s, bindns::bind(sleep_increment, ioc, count));
  }
  
  void throw_exception()
  {
    throw 1;
  }
  
  void io_context_run(io_context* ioc)
  {
    ioc->run();
  }
  
  void strand_test()
  {
    io_context ioc;
    io_context::strand s(ioc);
    int count = 0;
  
    post(ioc, bindns::bind(increment_without_lock, &s, &count));
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  
    ioc.run();
  
    // The run() call will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 1);
  
    count = 0;
    ioc.restart();
    post(s, bindns::bind(increment_with_lock, &s, &count));
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  
    ioc.run();
  
    // The run() call will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 1);
  
    count = 0;
    ioc.restart();
    post(ioc, bindns::bind(start_sleep_increments, &ioc, &s, &count));
    boost::asio::detail::thread thread1(bindns::bind(io_context_run, &ioc));
    boost::asio::detail::thread thread2(bindns::bind(io_context_run, &ioc));
  
    // Check all events run one after another even though there are two threads.
    timer timer1(ioc, chronons::seconds(3));
    timer1.wait();
    BOOST_ASIO_CHECK(count == 0);
  #if defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
    timer1.expires_at(timer1.expires_at() + chronons::seconds(2));
  #else // defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
    timer1.expires_at(timer1.expiry() + chronons::seconds(2));
  #endif // defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
    timer1.wait();
    BOOST_ASIO_CHECK(count == 1);
  #if defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
    timer1.expires_at(timer1.expires_at() + chronons::seconds(2));
  #else // defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
    timer1.expires_at(timer1.expiry() + chronons::seconds(2));
  #endif // defined(BOOST_ASIO_HAS_BOOST_DATE_TIME)
    timer1.wait();
    BOOST_ASIO_CHECK(count == 2);
  
    thread1.join();
    thread2.join();
  
    // The run() calls will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 3);
  
    count = 0;
    int exception_count = 0;
    ioc.restart();
    post(s, throw_exception);
    post(s, bindns::bind(increment, &count));
    post(s, bindns::bind(increment, &count));
    post(s, throw_exception);
    post(s, bindns::bind(increment, &count));
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
    BOOST_ASIO_CHECK(exception_count == 0);
  
    for (;;)
    {
      try
      {
        ioc.run();
        break;
      }
      catch (int)
      {
        ++exception_count;
      }
    }
  
    // The run() calls will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 3);
    BOOST_ASIO_CHECK(exception_count == 2);
  
    count = 0;
    ioc.restart();
  
    // Check for clean shutdown when handlers posted through an orphaned strand
    // are abandoned.
    {
      io_context::strand s2(ioc);
      post(s2, bindns::bind(increment, &count));
      post(s2, bindns::bind(increment, &count));
      post(s2, bindns::bind(increment, &count));
    }
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  }
  
  void strand_wrap_test()
  {
  #if !defined(BOOST_ASIO_NO_DEPRECATED)
    io_context ioc;
    io_context::strand s(ioc);
    int count = 0;
  
    s.wrap(bindns::bind(increment, &count))();
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  
    ioc.restart();
    ioc.run();
  
    // The run() calls will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 1);
  
    count = 0;
    s.wrap(increment)(&count);
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  
    ioc.restart();
    ioc.run();
  
    // The run() calls will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 1);
  
    count = 0;
    s.wrap(increment_by_a)(&count, 1);
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  
    ioc.restart();
    ioc.run();
  
    // The run() calls will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 1);
  
    count = 0;
    s.wrap(increment_by_a_b)(&count, 1, 2);
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  
    ioc.restart();
    ioc.run();
  
    // The run() calls will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 3);
  
    count = 0;
    s.wrap(increment_by_a_b_c)(&count, 1, 2, 3);
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  
    ioc.restart();
    ioc.run();
  
    // The run() calls will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 6);
  
    count = 0;
    s.wrap(increment_by_a_b_c_d)(&count, 1, 2, 3, 4);
  
    // No handlers can be called until run() is called.
    BOOST_ASIO_CHECK(count == 0);
  
    ioc.restart();
    ioc.run();
  
    // The run() calls will not return until all work has finished.
    BOOST_ASIO_CHECK(count == 10);
  #endif // !defined(BOOST_ASIO_NO_DEPRECATED)
  }
  
  BOOST_ASIO_TEST_SUITE
  (
    "strand",
    BOOST_ASIO_TEST_CASE(strand_test)
    BOOST_ASIO_TEST_CASE(strand_wrap_test)
  )
  