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1 | // |
2 | // parallel_grep.cpp | |
3 | // ~~~~~~~~~~~~~~~~~ | |
4 | // | |
11fdf7f2 | 5 | // Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com) |
b32b8144 FG |
6 | // |
7 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
8 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
9 | // | |
10 | ||
11 | #include <boost/asio/dispatch.hpp> | |
12 | #include <boost/asio/post.hpp> | |
13 | #include <boost/asio/spawn.hpp> | |
14 | #include <boost/asio/strand.hpp> | |
15 | #include <boost/asio/thread_pool.hpp> | |
16 | #include <fstream> | |
17 | #include <iostream> | |
18 | #include <string> | |
19 | ||
20 | using boost::asio::dispatch; | |
21 | using boost::asio::spawn; | |
22 | using boost::asio::strand; | |
23 | using boost::asio::thread_pool; | |
24 | using boost::asio::yield_context; | |
25 | ||
26 | int main(int argc, char* argv[]) | |
27 | { | |
28 | try | |
29 | { | |
30 | if (argc < 2) | |
31 | { | |
32 | std::cerr << "Usage: parallel_grep <string> <files...>\n"; | |
33 | return 1; | |
34 | } | |
35 | ||
36 | // We use a fixed size pool of threads for reading the input files. The | |
37 | // number of threads is automatically determined based on the number of | |
38 | // CPUs available in the system. | |
39 | thread_pool pool; | |
40 | ||
41 | // To prevent the output from being garbled, we use a strand to synchronise | |
42 | // printing. | |
43 | strand<thread_pool::executor_type> output_strand(pool.get_executor()); | |
44 | ||
45 | // Spawn a new coroutine for each file specified on the command line. | |
46 | std::string search_string = argv[1]; | |
47 | for (int argn = 2; argn < argc; ++argn) | |
48 | { | |
49 | std::string input_file = argv[argn]; | |
50 | spawn(pool, | |
51 | [=](yield_context yield) | |
52 | { | |
53 | std::ifstream is(input_file.c_str()); | |
54 | std::string line; | |
55 | std::size_t line_num = 0; | |
56 | while (std::getline(is, line)) | |
57 | { | |
58 | // If we find a match, send a message to the output. | |
59 | if (line.find(search_string) != std::string::npos) | |
60 | { | |
61 | dispatch(output_strand, | |
62 | [=] | |
63 | { | |
64 | std::cout << input_file << ':' << line << std::endl; | |
65 | }); | |
66 | } | |
67 | ||
68 | // Every so often we yield control to another coroutine. | |
69 | if (++line_num % 10 == 0) | |
70 | post(yield); | |
71 | } | |
72 | }); | |
73 | } | |
74 | ||
75 | // Join the thread pool to wait for all the spawned tasks to complete. | |
76 | pool.join(); | |
77 | } | |
78 | catch (std::exception& e) | |
79 | { | |
80 | std::cerr << "Exception: " << e.what() << "\n"; | |
81 | } | |
82 | ||
83 | return 0; | |
84 | } |