mirror of
https://github.com/matrix-construct/construct
synced 2024-11-30 02:32:43 +01:00
84 lines
2.7 KiB
C++
84 lines
2.7 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_CTX_CONTINUATION_H
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// This file is not included with the IRCd standard include stack because
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// it requires symbols we can't forward declare without boost headers. It
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// is part of the <ircd/asio.h> stack which can be included in your
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// definition file if necessary.
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namespace ircd::ctx
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{
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using yield_context = boost::asio::yield_context;
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struct continuation;
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struct to_asio;
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}
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namespace ircd
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{
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using ctx::yield_context;
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using ctx::continuation;
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using ctx::to_asio;
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}
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/// This object must be placed on the stack when the context is yielding (INTERNAL)
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///
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/// The continuation constructor is the last thing executed before a context
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/// yields. The continuation destructor is the first thing executed when a
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/// context continues. This is not placed by a normal user wishing to context
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/// switch, only a low-level library creator actually implementing the context
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/// switch itself. The placement of this object must be correct. Generally,
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/// we construct the `continuation` as an argument to `yield_context` as such
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/// `yield_context{continuation{}}`. This ensures the continuation destructor
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/// executes before control continues beyond the yield_context call itself and
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/// ties this sequence together neatly.
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///
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struct ircd::ctx::continuation
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{
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ctx *self;
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operator const boost::asio::yield_context &() const;
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operator boost::asio::yield_context &();
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virtual void interrupted(ctx *const &) noexcept;
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continuation(ctx *const &self = ircd::ctx::current);
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virtual ~continuation() noexcept;
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};
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/// This type of continuation should be used when yielding a context to a
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/// boost::asio handler so we can have specific control over that type of
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/// context switch in possible contrast or extension of the regular
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/// continuation behavior.
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///
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/// The statement `yield_context{to_asio{}}` can be passed to any boost::asio
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/// callback handler. Those handlers have overloads to accept this, many of
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/// which are not documented.
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///
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struct ircd::ctx::to_asio
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:ircd::ctx::continuation
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{
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using function = std::function<void (ctx *const &) noexcept>;
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function handler;
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void interrupted(ctx *const &) noexcept final override;
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to_asio(const function &handler = {});
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};
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inline
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ircd::ctx::to_asio::to_asio(const function &handler)
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:continuation{ircd::ctx::current}
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,handler{handler}
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{}
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