mirror of
https://github.com/matrix-construct/construct
synced 2024-09-12 11:39:27 +02:00
186 lines
4.7 KiB
C++
186 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_SHARED_STATE_H
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namespace ircd::ctx
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{
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struct shared_state_base;
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template<class T = void> struct shared_state;
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template<> struct shared_state<void>;
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template<class T> struct promise;
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template<> struct promise<void>;
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enum class future_state;
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template<class T> future_state state(const shared_state<T> &);
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template<class T> bool is(const shared_state<T> &, const future_state &);
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template<class T> void set(shared_state<T> &, const future_state &);
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template<> void set(shared_state<void> &, const future_state &);
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template<class T> void notify(shared_state<T> &);
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}
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/// Internal state enumeration for the promise / future / related. These can
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/// all be observed through state() or is(); only some can be set(). This is
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/// not for public manipulation.
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enum class ircd::ctx::future_state
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{
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INVALID, ///< Null.
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PENDING, ///< Promise is attached and busy.
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READY, ///< Result ready; promise is gone.
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OBSERVED, ///< Special case for when_*(); not a state; promise is gone.
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RETRIEVED, ///< User retrieved future value; promise is gone.
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};
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/// Internal Non-template base of the state object shared by promise and
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/// future. It is extended by the appropriate template, and usually resides
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/// in the future's instance, where the promise finds it.
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struct ircd::ctx::shared_state_base
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{
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mutable dock cond;
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std::exception_ptr eptr;
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std::function<void (shared_state_base &)> then;
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};
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/// Internal shared state between future and promise appropos a future value.
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template<class T>
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struct ircd::ctx::shared_state
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:shared_state_base
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{
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using value_type = T;
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using pointer_type = T *;
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using reference_type = T &;
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promise<T> *p {nullptr};
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T val;
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shared_state(promise<T> &p)
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:p{&p}
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{}
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shared_state() = default;
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};
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/// Internal shared state between future and promise when there is no future
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/// value, only a notification of completion or exception.
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template<>
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struct ircd::ctx::shared_state<void>
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:shared_state_base
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{
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using value_type = void;
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promise<void> *p {nullptr};
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shared_state(promise<void> &p)
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:p{&p}
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{}
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shared_state() = default;
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};
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/// Internal use
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template<class T>
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void
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ircd::ctx::notify(shared_state<T> &st)
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{
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if(!st.then)
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{
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st.cond.notify_all();
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return;
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}
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if(!current)
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{
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st.cond.notify_all();
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assert(bool(st.then));
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st.then(st);
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return;
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}
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const stack_usage_assertion sua;
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st.cond.notify_all();
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assert(bool(st.then));
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st.then(st);
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}
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/// Internal use
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template<class T>
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void
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ircd::ctx::set(shared_state<T> &st,
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const future_state &state)
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{
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wstrict-aliasing"
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switch(state)
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{
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case future_state::INVALID: assert(0); return;
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case future_state::PENDING: assert(0); return;
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case future_state::OBSERVED:
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case future_state::READY:
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reinterpret_cast<uintptr_t &>(st.p) = uintptr_t(0x42);
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return;
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case future_state::RETRIEVED:
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reinterpret_cast<uintptr_t &>(st.p) = uintptr_t(0x123);
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return;
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}
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#pragma GCC diagnostic pop
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}
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/// Internal use
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template<>
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inline void
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ircd::ctx::set(shared_state<void> &st,
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const future_state &state)
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{
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wstrict-aliasing"
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switch(state)
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{
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case future_state::INVALID: assert(0); return;
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case future_state::PENDING: assert(0); return;
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case future_state::READY:
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reinterpret_cast<uintptr_t &>(st.p) = uintptr_t(0x42);
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return;
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case future_state::OBSERVED:
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case future_state::RETRIEVED:
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reinterpret_cast<uintptr_t &>(st.p) = uintptr_t(0x123);
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return;
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}
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#pragma GCC diagnostic pop
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}
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/// Internal; check if the current state is something; safe but unnecessary
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/// for public use.
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template<class T>
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bool
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ircd::ctx::is(const shared_state<T> &st,
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const future_state &state_)
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{
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return state(st) == state_;
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}
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/// Internal; get the current state of the shared_state; safe but unnecessary
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/// for public use.
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template<class T>
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ircd::ctx::future_state
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ircd::ctx::state(const shared_state<T> &st)
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{
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switch(uintptr_t(st.p))
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{
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case 0x00: return future_state::INVALID;
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case 0x42: return future_state::READY;
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case 0x123: return future_state::RETRIEVED;
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default:
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assert(uintptr_t(st.p) >= 0x1000);
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return future_state::PENDING;
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}
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}
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