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
|
#include <boost/asio/associated_executor.hpp>
#include <boost/asio/bind_executor.hpp>
#include <boost/asio/execution.hpp>
#include <boost/asio/static_thread_pool.hpp>
#include <iostream>
#include <string>
using boost::asio::bind_executor;
using boost::asio::get_associated_executor;
using boost::asio::static_thread_pool;
namespace execution = boost::asio::execution;
// A function to asynchronously read a single line from an input stream.
template <class IoExecutor, class Handler>
void async_getline(IoExecutor io_ex, std::istream& is, Handler handler)
{
// Track work for the handler's associated executor.
auto work_ex = boost::asio::prefer(
get_associated_executor(handler, io_ex),
execution::outstanding_work.tracked);
// Post a function object to do the work asynchronously.
boost::asio::require(io_ex, execution::blocking.never).execute(
[&is, work_ex, handler=std::move(handler)]() mutable
{
std::string line;
std::getline(is, line);
// Pass the result to the handler, via the associated executor.
boost::asio::prefer(work_ex, execution::blocking.possibly).execute(
[line=std::move(line), handler=std::move(handler)]() mutable
{
handler(std::move(line));
});
});
}
// A function to asynchronously read multiple lines from an input stream.
template <class IoExecutor, class Handler>
void async_getlines(IoExecutor io_ex, std::istream& is, std::string init, Handler handler)
{
// Track work for the I/O executor.
auto io_work_ex = boost::asio::prefer(io_ex,
execution::outstanding_work.tracked);
// Track work for the handler's associated executor.
auto handler_work_ex = boost::asio::prefer(
get_associated_executor(handler, io_ex),
execution::outstanding_work.tracked);
// Use the associated executor for each operation in the composition.
async_getline(io_work_ex, is,
bind_executor(handler_work_ex,
[io_work_ex, &is, lines=std::move(init), handler=std::move(handler)]
(std::string line) mutable
{
if (line.empty())
handler(lines);
else
async_getlines(io_work_ex, is, lines + line + "\n", std::move(handler));
}));
}
int main()
{
static_thread_pool io_pool(1);
static_thread_pool completion_pool(1);
std::cout << "Enter text, terminating with a blank line:\n";
async_getlines(io_pool.executor(), std::cin, "",
bind_executor(completion_pool.executor(), [](std::string lines)
{
std::cout << "Lines:\n" << lines << "\n";
}));
io_pool.wait();
completion_pool.wait();
}
|
