mirror of
https://github.com/matrix-construct/construct
synced 2024-11-29 18:22:50 +01:00
136 lines
2.6 KiB
C++
136 lines
2.6 KiB
C++
/*
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* Copyright (C) 2016 Charybdis Development Team
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* Copyright (C) 2016 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.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#define HAVE_IRCD_CTX_MUTEX_H
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namespace ircd::ctx
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{
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class mutex;
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}
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//
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// The mutex only allows one context to lock it and continue,
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// additional contexts are queued. This can be used with std::
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// locking concepts.
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//
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class ircd::ctx::mutex
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{
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bool m;
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std::deque<ctx *> q;
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public:
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bool try_lock();
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template<class time_point> bool try_lock_until(const time_point &);
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template<class duration> bool try_lock_for(const duration &);
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void lock();
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void unlock();
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mutex();
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~mutex() noexcept;
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};
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inline
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ircd::ctx::mutex::mutex():
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m(false)
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{
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}
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inline
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ircd::ctx::mutex::~mutex()
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noexcept
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{
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assert(!m);
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assert(q.empty());
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}
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inline void
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ircd::ctx::mutex::unlock()
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{
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assert(m);
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ctx *next; do
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{
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if(!q.empty())
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{
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next = q.front();
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q.pop_front();
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}
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else next = nullptr;
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}
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while(next == &cur());
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m = false;
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if(next)
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yield(*next);
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}
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inline void
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ircd::ctx::mutex::lock()
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{
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if(likely(try_lock()))
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return;
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q.emplace_back(&cur());
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while(!try_lock())
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wait();
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}
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template<class duration>
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bool
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ircd::ctx::mutex::try_lock_for(const duration &d)
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{
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return try_lock_until(steady_clock::now() + d);
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}
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template<class time_point>
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bool
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ircd::ctx::mutex::try_lock_until(const time_point &tp)
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{
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if(likely(try_lock()))
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return true;
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q.emplace_back(&cur());
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while(!try_lock())
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{
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if(unlikely(wait_until<std::nothrow_t>(tp)))
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{
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const auto it(std::find(begin(q), end(q), &cur()));
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assert(it != end(q));
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q.erase(it);
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return false;
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}
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}
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return true;
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}
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inline bool
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ircd::ctx::mutex::try_lock()
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{
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if(m)
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return false;
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m = true;
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return true;
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}
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