/usr/include/bitcoin/utility/async_parallel.hpp is in libbitcoin-dev 2.0-2.4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | /*
* Copyright (c) 2011-2013 libbitcoin developers (see AUTHORS)
*
* This file is part of libbitcoin.
*
* libbitcoin is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License with
* additional permissions to the one published by the Free Software
* Foundation, either version 3 of the License, or (at your option)
* any later version. For more information see LICENSE.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef LIBBITCOIN_ASYNC_PARALLEL_HPP
#define LIBBITCOIN_ASYNC_PARALLEL_HPP
#include <atomic>
#include <memory>
#include <system_error>
#include <bitcoin/utility/assert.hpp>
namespace libbitcoin {
/*
* async_parallel(completion_handler, clearance_count)
*
* Returns a callback that will stop when:
*
* 1. An error is passed as the first argument.
* 2. It has been called clearance_count number of times.
*
* This is useful when we have a piece of code that forks into several
* asynchronous code paths. This utility ensures that all code paths
* are completed before calling the completion_handler.
*
* auto complete = [](std::error_code ec, std::string s) { ... };
* auto cb = async_parallel(complete, 3);
* cb(std::error_code, "hello");
* // Calling cb(error::service_stopped, "") here will
* // call complete(error::service_stopped, "")
* cb(std::error_code, "world");
* // Calls complete(std::error_code, "final")
* cb(std::error_code, "final");
*/
typedef std::atomic<size_t> atomic_counter;
typedef std::shared_ptr<atomic_counter> atomic_counter_ptr;
template <typename Handler>
struct async_parallel_dispatch
{
Handler handler;
size_t clearance_count;
atomic_counter_ptr counter;
template <typename... Args>
void operator()(const std::error_code& ec, Args&&... args)
{
BITCOIN_ASSERT(*counter <= clearance_count);
if (*counter == clearance_count)
return;
if (ec)
{
// Stop because of failure.
*counter = clearance_count;
handler(ec, std::forward<Args>(args)...);
}
else if (++(*counter) == clearance_count)
// Finished executing multiple async paths.
handler(ec, std::forward<Args>(args)...);
}
};
template <typename Handler>
async_parallel_dispatch<
typename std::decay<Handler>::type
>
async_parallel(Handler&& handler, size_t clearance_count)
{
return {handler, clearance_count,
std::make_shared<atomic_counter>(0)};
}
} // libbitcoin
#endif
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