1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
|
#include <boost/asio/dispatch.hpp>
#include <boost/asio/execution_context.hpp>
#include <condition_variable>
#include <iostream>
#include <memory>
#include <mutex>
#include <queue>
using boost::asio::dispatch;
using boost::asio::execution_context;
namespace execution = boost::asio::execution;
class priority_scheduler : public execution_context
{
public:
// A class that satisfies the Executor requirements.
class executor_type
{
public:
executor_type(priority_scheduler& ctx, int pri) noexcept
: context_(ctx), priority_(pri)
{
}
priority_scheduler& query(execution::context_t) const noexcept
{
return context_;
}
template <class Func>
void execute(Func f) const
{
auto p(std::make_shared<item<Func>>(priority_, std::move(f)));
std::lock_guard<std::mutex> lock(context_.mutex_);
context_.queue_.push(p);
context_.condition_.notify_one();
}
friend bool operator==(const executor_type& a,
const executor_type& b) noexcept
{
return &a.context_ == &b.context_;
}
friend bool operator!=(const executor_type& a,
const executor_type& b) noexcept
{
return &a.context_ != &b.context_;
}
private:
priority_scheduler& context_;
int priority_;
};
~priority_scheduler() noexcept
{
shutdown();
destroy();
}
executor_type get_executor(int pri = 0) noexcept
{
return executor_type(*const_cast<priority_scheduler*>(this), pri);
}
void run()
{
std::unique_lock<std::mutex> lock(mutex_);
for (;;)
{
condition_.wait(lock, [&]{ return stopped_ || !queue_.empty(); });
if (stopped_)
return;
auto p(queue_.top());
queue_.pop();
lock.unlock();
p->execute_(p);
lock.lock();
}
}
void stop()
{
std::lock_guard<std::mutex> lock(mutex_);
stopped_ = true;
condition_.notify_all();
}
private:
struct item_base
{
int priority_;
void (*execute_)(std::shared_ptr<item_base>&);
};
template <class Func>
struct item : item_base
{
item(int pri, Func f) : function_(std::move(f))
{
priority_ = pri;
execute_ = [](std::shared_ptr<item_base>& p)
{
Func tmp(std::move(static_cast<item*>(p.get())->function_));
p.reset();
tmp();
};
}
Func function_;
};
struct item_comp
{
bool operator()(
const std::shared_ptr<item_base>& a,
const std::shared_ptr<item_base>& b)
{
return a->priority_ < b->priority_;
}
};
std::mutex mutex_;
std::condition_variable condition_;
std::priority_queue<
std::shared_ptr<item_base>,
std::vector<std::shared_ptr<item_base>>,
item_comp> queue_;
bool stopped_ = false;
};
int main()
{
priority_scheduler sched;
auto low = sched.get_executor(0);
auto med = sched.get_executor(1);
auto high = sched.get_executor(2);
dispatch(low, []{ std::cout << "1\n"; });
dispatch(low, []{ std::cout << "11\n"; });
dispatch(med, []{ std::cout << "2\n"; });
dispatch(med, []{ std::cout << "22\n"; });
dispatch(high, []{ std::cout << "3\n"; });
dispatch(high, []{ std::cout << "33\n"; });
dispatch(high, []{ std::cout << "333\n"; });
dispatch(sched.get_executor(-1), [&]{ sched.stop(); });
sched.run();
}
|
