thread_helper_functions.hpp

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/*
 * SObjectizer-5
 */
 
/*!
 * \file
 * \brief Helper functions for working with threads.
 * \since
 * v.5.5.16
 */
 
#pragma once
 
#include <array>
#include <thread>
 
namespace so_5 {
 
namespace thread_auto_join_details {
 
/*!
 * \brief Main class for auto join operation.
 *
 * \attention This is Moveable class, not Copyable.
 *
 * \since
 * v.5.5.16
 */
template< std::size_t N >
class auto_joiner_t
  {
    std::array< std::thread *, N > m_threads;
 
    void
    nullify() { m_threads.fill( nullptr ); }
 
  public :
    auto_joiner_t( const auto_joiner_t & ) = delete;
    auto_joiner_t & operator=( const auto_joiner_t & ) = delete;
 
    auto_joiner_t()
      {
        nullify();
      }
 
    auto_joiner_t( auto_joiner_t && o ) noexcept
      {
        nullify();
        m_threads.swap( o.m_threads );
      }
 
    ~auto_joiner_t()
      {
        for( auto t : m_threads )
          if( t && t->joinable() )
            t->join();
      }
 
    friend inline void
    swap( auto_joiner_t & a, auto_joiner_t & b ) noexcept
      {
        using std::swap;
        swap( a.m_threads, b.m_threads );
      }
 
    auto_joiner_t &
    operator=( auto_joiner_t && o ) noexcept
      {
        auto_joiner_t tmp{ std::move(o) };
        swap( *this, tmp );
        return *this;
      }
 
    void
    set_thread( std::size_t index, std::thread & t )
      {
        m_threads[ index ] = &t;
      }
  };
 
/*!
 * \brief Helper for filling auto_joiner object.
 *
 * \since
 * v.5.5.16
 */
template< typename Joiner >
void
add_to_joiner( Joiner & to, std::size_t index, std::thread & t )
  {
    to.set_thread( index, t );
  }
 
/*!
 * \brief Helper for filling auto_joiner object.
 *
 * \since
 * v.5.5.16
 */
template< typename Joiner, typename... Tail >
void
add_to_joiner(
  Joiner & to,
  std::size_t index,
  std::thread & t,
  Tail &&... tail )
  {
    add_to_joiner( to, index, t );
    add_to_joiner( to, index + 1, std::forward< Tail >(tail)... );
  }
 
} /* namespace thread_auto_join_details */
 
/*!
 * \brief Helper function for creation of automatic joiner of std::threads.
 *
 * Usage examples:
 * \code
  std::thread first_worker;
  std::thread second_worker;
  auto worker_joiner = so_5::auto_join( first_worker, second_worker );
 
  first_worker = thread{ ... };
  second_worker = thread{ ... };
  ...
 * \endcode
 *
 * \since
 * v.5.5.16
 */
template< typename... Tail >
thread_auto_join_details::auto_joiner_t< 1 + sizeof...(Tail) >
auto_join(
  //! The first thread to be closed.
  std::thread & first_thread,
  //! Other threads to be closed.
  Tail &&... tail )
  {
    using namespace thread_auto_join_details;
 
    auto_joiner_t< 1 + sizeof...(tail) > joiner;
    add_to_joiner( joiner, 0, first_thread, std::forward< Tail >(tail)... );
 
    return joiner;
  }
 
} /* namespace so_5 */