context/example/execution_context/coroutine/layout.cpp

//          Copyright Nat Goodspeed 2013.
//          Copyright Oliver Kowalke 2014.
// 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)

#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <utility>

#include <boost/context/fixedsize.hpp>

#include "coroutine.hpp"

struct FinalEOL{
    ~FinalEOL(){
        std::cout << std::endl;
    }
};

typedef coroutine< std::string >    coro_t;

int main(int argc,char* argv[]){
    std::vector<std::string> words{
        "peas", "porridge", "hot", "peas",
        "porridge", "cold", "peas", "porridge",
        "in", "the", "pot", "nine",
        "days", "old" };

    int num=5,width=15;
    coro_t::push_type writer( boost::context::fixedsize(),
                              [&](coro_t::pull_type& in){
                                  // finish the last line when we leave by whatever means
                                  FinalEOL eol;
                                  // pull values from upstream, lay them out 'num' to a line
                                  for (;;){
                                      for(int i=0;i<num;++i){
                                          // when we exhaust the input, stop
                                          if(!in) return;
                                          std::cout << std::setw(width) << in.get();
                                          // now that we've handled this item, advance to next
                                          in();
                                      }
                                      // after 'num' items, line break
                                      std::cout << std::endl;
                                  }
                              });

    std::vector<std::string>::iterator i = words.begin();
    std::vector<std::string>::iterator e = words.end();
    while ( i != e) {
        std::string w( * i);
        writer( w);
        ++i;
    }

    std::cout << "\nDone" << std::endl;

    return 0;
}