mirror of
https://github.com/matrix-construct/construct
synced 2024-11-05 21:38:54 +01:00
100 lines
2.7 KiB
C++
100 lines
2.7 KiB
C++
// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk
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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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#pragma once
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#define HAVE_IRCD_UTIL_UNWIND_H
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namespace ircd::util
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{
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struct unwind;
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};
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//
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// Fundamental scope-unwind utilities establishing actions during destruction
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//
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/// Unconditionally executes the provided code when the object goes out of scope.
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///
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struct ircd::util::unwind
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{
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struct nominal;
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struct exceptional;
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const std::function<void ()> func;
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template<class F>
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unwind(F &&func)
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:func{std::forward<F>(func)}
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{}
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unwind(const unwind &) = delete;
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unwind &operator=(const unwind &) = delete;
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~unwind() noexcept
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{
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func();
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}
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};
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/// Executes function only if the unwind takes place without active exception
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///
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/// The function is expected to be executed and the likely() should pipeline
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/// that branch and make this device cheaper to use under normal circumstances.
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///
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struct ircd::util::unwind::nominal
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{
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const std::function<void ()> func;
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template<class F>
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nominal(F &&func)
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:func{std::forward<F>(func)}
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{}
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~nominal() noexcept
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{
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if(likely(!std::uncaught_exception()))
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func();
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}
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nominal(const nominal &) = delete;
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};
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/// Executes function only if unwind is taking place because exception thrown
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///
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/// The unlikely() intends for the cost of a branch misprediction to be paid
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/// for fetching and executing this function. This is because we strive to
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/// optimize the pipeline for the nominal path, making this device as cheap
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/// as possible to use.
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///
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struct ircd::util::unwind::exceptional
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{
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const std::function<void ()> func;
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template<class F>
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exceptional(F &&func)
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:func{std::forward<F>(func)}
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{}
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~exceptional() noexcept
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{
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if(unlikely(std::uncaught_exception()))
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func();
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}
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exceptional(const exceptional &) = delete;
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};
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