mirror of
https://github.com/matrix-construct/construct
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127 lines
4.6 KiB
C++
127 lines
4.6 KiB
C++
/*
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* charybdis: oh just a little chat server
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* ctx.h: userland context switching (stackful coroutines)
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*
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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_CONTEXT_H
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namespace ircd::ctx
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{
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struct context;
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const size_t DEFAULT_STACK_SIZE
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{
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64_KiB
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};
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}
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/// Principal interface for a context.
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///
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/// This object creates, holds and destroys a context with an interface
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/// similar to that of std::thread.
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///
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/// The function passed to the constructor is executed on a new stack. By
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/// default this execution will start to occur before this object is even
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/// fully constructed. To delay child execution pass the `POST` flag to
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/// the constructor; the execution will then be posted to the io_service
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/// event queue instead. `DISPATCH` is an alternative, see boost::asio docs.
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///
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/// When this object goes out of scope the context is interrupted and joined
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/// if it has not been already; the current context will wait for this to
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/// complete. If the child context does not cooperate the destructor will hang.
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/// To prevent this behavior `detach()` the ctx from this handler object; the
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/// detached context will free its own resources when finished executing.
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///
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/// To wait for the child context to finish use `join()`. Calling `interrupt()`
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/// will cause an `interrupted` exception to be thrown down the child's stack
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/// from the next interruption point; a context switch is an interruption point
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/// and so the context will wake up in its exception handler.
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///
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struct ircd::ctx::context
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{
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enum flags :uint;
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using function = std::function<void ()>;
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private:
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std::unique_ptr<ctx> c;
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public:
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operator const ctx &() const { return *c; }
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operator ctx &() { return *c; }
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bool operator!() const { return !c; }
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operator bool() const { return bool(c); }
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bool joined() const { return !c || ircd::ctx::finished(*c); }
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void interrupt() { ircd::ctx::interrupt(*c); }
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void join(); // Blocks the current context until this one finishes
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ctx *detach(); // other calls undefined after this call
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// Note: Constructing with DETACH flag makes any further use of this object undefined.
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context(const char *const &name,
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const size_t &stack_size,
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const flags &,
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function);
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context(const char *const &name,
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const size_t &stack_size,
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function,
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const flags & = (flags)0);
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context(const char *const &name,
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const flags &,
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function);
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context(const char *const &name,
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function,
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const flags & = (flags)0);
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context(function,
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const flags & = (flags)0);
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context() = default;
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context(context &&) = default;
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context(const context &) = delete;
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context &operator=(context &&) = default;
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context &operator=(const context &) = delete;
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~context() noexcept;
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friend void swap(context &a, context &b) noexcept;
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};
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enum ircd::ctx::context::flags
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:uint
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{
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POST = 0x01, ///< Defers spawn with an ios.post()
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DISPATCH = 0x02, ///< Defers spawn with an ios.dispatch() (possibly)
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DETACH = 0x04, ///< Context deletes itself; see struct context constructor notes
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INTERRUPTED = 0x10, ///< (INDICATOR) Marked
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};
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inline void
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ircd::ctx::swap(context &a, context &b)
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noexcept
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{
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std::swap(a.c, b.c);
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}
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