vMP6st4s

1#define BOOST_THREAD_PROVIDES_FUTURE 
2#define BOOST_THREAD_PROVIDES_FUTURE_CONTINUATION
3#include <boost/fiber/future/future.hpp>
4#include <boost/fiber/future/async.hpp>
5#include <boost/thread.hpp>
6#include <iostream>
7#include <vector>
8#include <unordered_map>
9#include <string>
10#include <memory>
11
12/////////////////////////////////////////////////////////////////
13// Helpers
14struct PairHash
15{
16    template <class T1, class T2>
17    std::size_t operator() (const std::pair<T1, T2> &pair) const {
18        return std::hash<T1>()(pair.first) ^ std::hash<T2>()(pair.second);
19    }
20};
21
22class Dataset
23{
24public:
25    using Row = int;
26    using Column = std::string;
27    using Value = int;
28    using ValueMap = std::unordered_map<std::pair<Row, Column>, Value, PairHash>;
29
30    using Ptr = std::shared_ptr<Dataset>;
31    
32    explicit Dataset( const ValueMap& values) : m_values{ values }
33    {}
34    Value getContent(Row row, Column column) const
35    {
36       const auto valIt = m_values.find({ row, column });
37       return valIt != m_values.cend() ? valIt->second : Value{};
38    }
39  
40private:
41    ValueMap m_values;
42};
43
44namespace bf = boost;
45
46/////////////////////////////////////////////////////////////////
47// Example of async API
48class AsyncDataProvider
49{
50    public:
51    bf::future<Dataset::Ptr> loadDataForRow(Dataset::Row row) const
52    {
53        return bf::async([&]
54        {
55            boost::this_thread::sleep_for(boost::chrono::seconds{ 2 });
56            return std::make_shared<Dataset>(Dataset::ValueMap{ { { row , "key" }, row }, { { row , "type" }, 0 }  });
57        });
58    }
59};
60
61/////////////////////////////////////////////////////////////////
62int main()
63{
64   AsyncDataProvider provider{};
65   
66   Dataset::Row row{ 1 };
67   // Asynchronous use (in the GUI)
68   std::cout << "Asynchronous use \n";
69   auto future = provider.loadDataForRow(row);
70   future.then([&](auto f)
71   {
72       const auto dataset = f.get();
73       std::cout << "Async getContent(): " << dataset->getContent(row, "key") << std::endl;
74   });
75    
76   // Synchronous use (in the data model business logic)
77   std::cout << "Synchronous use \n";
78   auto dataset = provider.loadDataForRow(row).get();
79   
80   std::cout << "Sync getContent(): " << dataset->getContent(row, "key") << std::endl;
81
82   std::cout << "end\n";
83}