mirror of
https://github.com/matrix-construct/construct
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124 lines
4.5 KiB
C++
124 lines
4.5 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_CONTEXT_H
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namespace ircd::ctx
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{
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struct context;
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extern const size_t DEFAULT_STACK_SIZE;
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void swap(context &a, context &b) noexcept;
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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 :uint32_t;
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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 terminate() { ircd::ctx::terminate(*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 string_view &name,
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const mutable_buffer &stack,
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const flags &,
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function);
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context(const string_view &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 string_view &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 string_view &name,
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const flags &,
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function);
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context(const string_view &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();
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context(context &&) noexcept;
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context(const context &) = delete;
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context &operator=(context &&) noexcept;
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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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:uint32_t
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{
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POST = 0x0001, ///< Defers spawn with an ios.post()
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DISPATCH = 0x0002, ///< Defers spawn with an ios.dispatch()
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DEFER = 0x0004, ///< Defers spawn with an ios.defer()
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DETACH = 0x0008, ///< Context deletes itself; see struct context constructor notes
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NOINTERRUPT = 0x0010, ///< Interruption points won't throw while lit.
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SLICE_EXEMPT = 0x0020, ///< The watchdog will ignore excessive cpu usage.
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STACK_EXEMPT = 0x0040, ///< The watchdog will ignore excessive stack usage.
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WAIT_JOIN = 0x0080, ///< Destruction of instance won't terminate ctx.
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INTERRUPTED = 0x4000, ///< (INDICATOR) Marked
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TERMINATED = 0x8000, ///< (INDICATOR)
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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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