mirror of
https://github.com/matrix-construct/construct
synced 2024-08-28 20:35:16 +02:00
246 lines
4.7 KiB
C++
246 lines
4.7 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_DOCK_H
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namespace ircd::ctx
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{
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struct dock;
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enum class cv_status;
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}
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/// dock is a condition variable which has no requirement for locking because
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/// the context system does not require mutual exclusion for coherence.
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///
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class ircd::ctx::dock
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{
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list q;
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void notify(ctx &) noexcept;
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public:
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bool empty() const;
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size_t size() const;
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template<class time_point, class predicate> bool wait_until(time_point&& tp, predicate&& pred);
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template<class time_point> cv_status wait_until(time_point&& tp);
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template<class duration, class predicate> bool wait_for(const duration &dur, predicate&& pred);
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template<class duration> cv_status wait_for(const duration &dur);
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template<class predicate> void wait(predicate&& pred);
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void wait();
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void notify_all() noexcept;
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void notify_one() noexcept;
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void notify() noexcept;
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};
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enum class ircd::ctx::cv_status
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{
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no_timeout, timeout
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};
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/// Wake up the next context waiting on the dock
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///
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/// Unlike notify_one(), the next context in the queue is repositioned in the
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/// back before being woken up for fairness.
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inline void
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ircd::ctx::dock::notify()
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noexcept
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{
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ctx *c;
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if(!(c = q.pop_front()))
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return;
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q.push_back(c);
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notify(*c);
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}
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/// Wake up the next context waiting on the dock
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inline void
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ircd::ctx::dock::notify_one()
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noexcept
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{
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if(!q.empty())
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notify(*q.front());
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}
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/// Wake up all contexts waiting on the dock.
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///
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/// We post all notifications without requesting direct context
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/// switches. This ensures everyone gets notified in a single
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/// transaction without any interleaving during this process.
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inline void
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ircd::ctx::dock::notify_all()
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noexcept
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{
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q.for_each([](ctx &c)
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{
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ircd::ctx::notify(c);
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});
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}
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inline void
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ircd::ctx::dock::wait()
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{
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assert(current);
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const unwind remove{[this]
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{
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q.remove(current);
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}};
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q.push_back(current);
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ircd::ctx::wait();
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}
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template<class predicate>
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void
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ircd::ctx::dock::wait(predicate&& pred)
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{
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if(pred())
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return;
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assert(current);
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const unwind remove{[this]
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{
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q.remove(current);
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}};
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q.push_back(current); do
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{
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ircd::ctx::wait();
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}
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while(!pred());
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}
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template<class duration>
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ircd::ctx::cv_status
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ircd::ctx::dock::wait_for(const duration &dur)
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{
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static const duration zero(0);
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assert(current);
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const unwind remove{[this]
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{
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q.remove(current);
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}};
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q.push_back(current);
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return ircd::ctx::wait<std::nothrow_t>(dur) > zero? cv_status::no_timeout:
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cv_status::timeout;
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}
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template<class duration,
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class predicate>
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bool
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ircd::ctx::dock::wait_for(const duration &dur,
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predicate&& pred)
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{
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static const duration zero(0);
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if(pred())
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return true;
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assert(current);
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const unwind remove{[this]
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{
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q.remove(current);
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}};
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q.push_back(current); do
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{
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const bool expired(ircd::ctx::wait<std::nothrow_t>(dur) <= zero);
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if(pred())
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return true;
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if(expired)
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return false;
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}
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while(1);
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}
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template<class time_point>
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ircd::ctx::cv_status
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ircd::ctx::dock::wait_until(time_point&& tp)
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{
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assert(current);
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const unwind remove{[this]
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{
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q.remove(current);
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}};
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q.push_back(current);
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return ircd::ctx::wait_until<std::nothrow_t>(tp)? cv_status::timeout:
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cv_status::no_timeout;
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}
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template<class time_point,
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class predicate>
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bool
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ircd::ctx::dock::wait_until(time_point&& tp,
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predicate&& pred)
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{
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if(pred())
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return true;
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assert(current);
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const unwind remove{[this]
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{
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q.remove(current);
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}};
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q.push_back(current); do
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{
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const bool expired
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{
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ircd::ctx::wait_until<std::nothrow_t>(tp)
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};
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if(pred())
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return true;
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if(expired)
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return false;
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}
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while(1);
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}
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inline void
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ircd::ctx::dock::notify(ctx &ctx)
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noexcept
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{
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// This branch handles dock.notify() being called from outside the context system.
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// If a context is currently running we can make a direct context-switch with
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// yield(ctx), otherwise notify(ctx) enqueues the context.
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if(current)
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ircd::ctx::yield(ctx);
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else
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ircd::ctx::notify(ctx);
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}
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/// The number of contexts waiting in the queue.
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inline size_t
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ircd::ctx::dock::size()
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const
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{
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return q.size();
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}
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/// The number of contexts waiting in the queue.
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inline bool
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ircd::ctx::dock::empty()
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const
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{
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return q.empty();
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}
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