ceph/src/seastar/demos/coroutines_demo.cc

   1 /*
   2  * This file is open source software, licensed to you under the terms
   3  * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
   4  * distributed with this work for additional information regarding copyright
   5  * ownership.  You may not use this file except in compliance with the License.
   6  *
   7  * You may obtain a copy of the License at
   8  *
   9  *   http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing,
  12  * software distributed under the License is distributed on an
  13  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  14  * KIND, either express or implied.  See the License for the
  15  * specific language governing permissions and limitations
  16  * under the License.
  17  */
  18 /*
  19  * Copyright (C) 2019 ScyllaDB Ltd.
  20  */
  21
  22 #include <seastar/core/app-template.hh>
  23 #include <seastar/core/coroutine.hh>
  24 #include <seastar/core/fstream.hh>
  25 #include <seastar/core/reactor.hh>
  26 #include <seastar/core/sleep.hh>
  27
  28 int main(int argc, char** argv) {
  29     seastar::app_template app;
  30     app.run(argc, argv, [] () -> seastar::future<> {
  31         std::cout << "this is a completely useless program\nplease stand by...\n";
  32         auto f = seastar::parallel_for_each(std::vector<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }, [] (int i) -> seastar::future<> {
  33             co_await seastar::sleep(std::chrono::seconds(i));
  34             std::cout << i << "\n";
  35         });
  36
  37         auto file = co_await seastar::open_file_dma("useless_file.txt", seastar::open_flags::create | seastar::open_flags::wo);
  38         auto out = seastar::make_file_output_stream(file);
  39         seastar::sstring str = "nothing to see here, move along now\n";
  40         co_await out.write(str);
  41         co_await out.flush();
  42         co_await out.close();
  43
  44         co_await std::move(f);
  45         std::cout << "done\n";
  46     });
  47 }