parallel_grep.cpp
2.22 KB
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
//
// parallel_grep.cpp
// ~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// 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 <asio/dispatch.hpp>
#include <asio/post.hpp>
#include <asio/spawn.hpp>
#include <asio/strand.hpp>
#include <asio/thread_pool.hpp>
#include <fstream>
#include <iostream>
#include <string>
using asio::dispatch;
using asio::spawn;
using asio::strand;
using asio::thread_pool;
using asio::yield_context;
int main(int argc, char* argv[])
{
try
{
if (argc < 2)
{
std::cerr << "Usage: parallel_grep <string> <files...>\n";
return 1;
}
// We use a fixed size pool of threads for reading the input files. The
// number of threads is automatically determined based on the number of
// CPUs available in the system.
thread_pool pool;
// To prevent the output from being garbled, we use a strand to synchronise
// printing.
strand<thread_pool::executor_type> output_strand(pool.get_executor());
// Spawn a new coroutine for each file specified on the command line.
std::string search_string = argv[1];
for (int argn = 2; argn < argc; ++argn)
{
std::string input_file = argv[argn];
spawn(pool,
[=](yield_context yield)
{
std::ifstream is(input_file.c_str());
std::string line;
std::size_t line_num = 0;
while (std::getline(is, line))
{
// If we find a match, send a message to the output.
if (line.find(search_string) != std::string::npos)
{
dispatch(output_strand,
[=]
{
std::cout << input_file << ':' << line << std::endl;
});
}
// Every so often we yield control to another coroutine.
if (++line_num % 10 == 0)
post(yield);
}
});
}
// Join the thread pool to wait for all the spawned tasks to complete.
pool.join();
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}