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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2018 Red Hat, Inc
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#pragma once
#include <boost/range/begin.hpp>
#include <boost/range/end.hpp>
#include <boost/asio/io_context.hpp>
#include "acconfig.h"
#include <spawn/spawn.hpp>
// use explicit executor types instead of the type-erased boost::asio::executor.
// coroutines wrap the default io_context executor with a strand executor
using yield_context = spawn::basic_yield_context<
boost::asio::executor_binder<void(*)(),
boost::asio::strand<boost::asio::io_context::executor_type>>>;
/// optional-like wrapper for a spawn::yield_context and its associated
/// boost::asio::io_context. operations that take an optional_yield argument
/// will, when passed a non-empty yield context, suspend this coroutine instead
/// of the blocking the thread of execution
class optional_yield {
boost::asio::io_context *c = nullptr;
yield_context *y = nullptr;
public:
/// construct with a valid io and yield_context
explicit optional_yield(boost::asio::io_context& c,
yield_context& y) noexcept
: c(&c), y(&y) {}
/// type tag to construct an empty object
struct empty_t {};
optional_yield(empty_t) noexcept {}
/// implicit conversion to bool, returns true if non-empty
operator bool() const noexcept { return y; }
/// return a reference to the associated io_context. only valid if non-empty
boost::asio::io_context& get_io_context() const noexcept { return *c; }
/// return a reference to the yield_context. only valid if non-empty
yield_context& get_yield_context() const noexcept { return *y; }
};
// type tag object to construct an empty optional_yield
static constexpr optional_yield::empty_t null_yield{};
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