Boost asio只需要在m个工作完成后发布n个工作

thx, dodol

#include <boost/asio.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/bind.hpp>
#include <iostream>
boost::mutex global_stream_lock;
boost::mutex mx;
boost::condition_variable cv;
void WorkerThread( boost::shared_ptr< boost::asio::io_service > io_service)
{
    global_stream_lock.lock();
    std::cout << "[" << boost::this_thread::get_id()
        << "] Thread Start" << std::endl;
    global_stream_lock.unlock();
    io_service->run();
    global_stream_lock.lock();
    std::cout << "[" << boost::this_thread::get_id()
        << "] Thread Finish" << std::endl;
    global_stream_lock.unlock();
}
size_t fib( size_t n )
{
    if ( n <= 1 )
    {
        return n;
    }
    boost::this_thread::sleep( 
        boost::posix_time::milliseconds( 1000 )
        );
    return fib( n - 1 ) + fib( n - 2);
}
void CalculateFib( size_t n )
{
    global_stream_lock.lock();
    std::cout << "[" << boost::this_thread::get_id()
        << "] Now calculating fib( " << n << " ) " << std::endl;
    global_stream_lock.unlock();
    size_t f = fib( n );
    global_stream_lock.lock();
    std::cout << "[" << boost::this_thread::get_id()
        << "] fib( " << n << " ) = " << f << std::endl;
    global_stream_lock.unlock();
    boost::lock_guard<boost::mutex> lk(mx);
    cv.notify_all();
}
void CalculateFib2( size_t n )
{
    boost::unique_lock<boost::mutex> lk(mx);
    cv.wait(lk);
    global_stream_lock.lock();
    std::cout << "[" << boost::this_thread::get_id()
        << "] Now calculating fib2( " << n << " ) " << std::endl;
    global_stream_lock.unlock();
    size_t f = fib( n );
    global_stream_lock.lock();
    std::cout << "[" << boost::this_thread::get_id()
        << "] fib2( " << n << " ) = " << f << std::endl;
    global_stream_lock.unlock();
}
int main( int argc, char * argv[] )
{
    boost::shared_ptr< boost::asio::io_service > io_service(
        new boost::asio::io_service
        );
    boost::shared_ptr< boost::asio::io_service::work > work(
        new boost::asio::io_service::work( *io_service )
        );
    global_stream_lock.lock();
    std::cout << "[" << boost::this_thread::get_id()
        << "] The program will exit when all work has finished."
        << std::endl;
    global_stream_lock.unlock();
    boost::thread_group worker_threads;
    for( int x = 0; x < 2; ++x )
    {
        worker_threads.create_thread( 
            boost::bind( &WorkerThread, io_service )
            );
    }
    io_service->post( boost::bind( CalculateFib, 5 ) );
    io_service->post( boost::bind( CalculateFib, 4 ) );
    io_service->post( boost::bind( CalculateFib, 3 ) );
    io_service->post( boost::bind( CalculateFib2, 1 ) );
    io_service->post( boost::bind( CalculateFib2, 1 ) );
    work.reset();
    worker_threads.join_all();
    return 0;
}