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construct/include/ircd/ctx/continuation.h

74 lines
2.6 KiB
C++

// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
#pragma once
#define HAVE_IRCD_CTX_CONTINUATION_H
// This file is not included with the IRCd standard include stack because
// it requires symbols we can't forward declare without boost headers. It
// is part of the <ircd/asio.h> stack which can be included in your
// definition file if necessary.
namespace ircd::ctx
{
struct continuation;
using yield_context = boost::asio::yield_context;
using yield_closure = std::function<void (yield_context &)>;
using interruptor = std::function<void (ctx *const &)>;
using predicate = std::function<bool ()>;
}
namespace ircd
{
using ctx::continuation;
}
/// This object must be placed on the stack when the context is yielding (INTERNAL)
///
/// The instance contains references to some callables which must remain valid.
///
/// - predicate (NOT YET USED)
/// A wakeup condition. This should be a simple boolean function which
/// tests whether the context should be woken up. The continuation references
/// this to convey the condition to a scheduler which may test many predicates
/// while contexts are asleep and then determine a schedule. This is an
/// alternative to waking up contexts first to test their predicates.
///
/// - interruptor
/// An interruption action. This is called when a context cannot wakeup on its
/// own after receiving an interruption without help from this action. Common
/// use for this is with yields to asio.
///
struct ircd::ctx::continuation
{
static const predicate asio_predicate;
static const predicate true_predicate;
static const predicate false_predicate;
static const interruptor noop_interruptor;
ctx *const self;
const predicate *const pred;
const interruptor *const intr;
const uint uncaught_exceptions;
operator const boost::asio::yield_context &() const noexcept;
operator boost::asio::yield_context &() noexcept;
continuation(const predicate &,
const interruptor &,
const yield_closure &);
continuation(continuation &&) = delete;
continuation(const continuation &) = delete;
continuation &operator=(continuation &&) = delete;
continuation &operator=(const continuation &) = delete;
~continuation() noexcept;
};