mirror of
https://github.com/matrix-construct/construct
synced 2024-10-30 10:28:55 +01:00
137 lines
3.1 KiB
C++
137 lines
3.1 KiB
C++
// Matrix Construct
|
|
//
|
|
// Copyright (C) Matrix Construct Developers, Authors & Contributors
|
|
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice is present in all copies. The
|
|
// full license for this software is available in the LICENSE file.
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_UTIL_UNWIND_H
|
|
|
|
namespace ircd::util
|
|
{
|
|
struct unwind;
|
|
};
|
|
|
|
//
|
|
// Fundamental scope-unwind utilities establishing actions during destruction
|
|
//
|
|
|
|
/// Unconditionally executes the provided code when the object goes out of scope.
|
|
///
|
|
struct ircd::util::unwind
|
|
{
|
|
struct defer;
|
|
struct nominal;
|
|
struct exceptional;
|
|
|
|
const std::function<void ()> func;
|
|
|
|
template<class F>
|
|
unwind(F&& func)
|
|
:func{std::forward<F>(func)}
|
|
{}
|
|
|
|
unwind(const unwind &) = delete;
|
|
unwind &operator=(const unwind &) = delete;
|
|
~unwind() noexcept
|
|
{
|
|
func();
|
|
}
|
|
};
|
|
|
|
/// Executes function only if the unwind takes place without active exception
|
|
///
|
|
/// The function is expected to be executed and the likely() should pipeline
|
|
/// that branch and make this device cheaper to use under normal circumstances.
|
|
///
|
|
struct ircd::util::unwind::nominal
|
|
{
|
|
struct assertion;
|
|
|
|
const std::function<void ()> func;
|
|
|
|
template<class F>
|
|
nominal(F&& func)
|
|
:func{std::forward<F>(func)}
|
|
{}
|
|
|
|
~nominal() noexcept
|
|
{
|
|
if(likely(!std::uncaught_exceptions()))
|
|
func();
|
|
}
|
|
|
|
nominal(const nominal &) = delete;
|
|
};
|
|
|
|
/// Executes function only if unwind is taking place because exception thrown
|
|
///
|
|
/// The unlikely() intends for the cost of a branch misprediction to be paid
|
|
/// for fetching and executing this function. This is because we strive to
|
|
/// optimize the pipeline for the nominal path, making this device as cheap
|
|
/// as possible to use.
|
|
///
|
|
struct ircd::util::unwind::exceptional
|
|
{
|
|
struct assertion;
|
|
|
|
const std::function<void ()> func;
|
|
|
|
template<class F>
|
|
exceptional(F&& func)
|
|
:func{std::forward<F>(func)}
|
|
{}
|
|
|
|
~exceptional() noexcept
|
|
{
|
|
if(unlikely(std::uncaught_exceptions()))
|
|
func();
|
|
}
|
|
|
|
exceptional(const exceptional &) = delete;
|
|
};
|
|
|
|
/// Posts function to the event loop at the unwind rather than executing it
|
|
/// as with nominal/exceptional.
|
|
///
|
|
struct ircd::util::unwind::defer
|
|
{
|
|
std::function<void ()> func;
|
|
|
|
template<class F>
|
|
defer(F&& func)
|
|
:func{std::forward<F>(func)}
|
|
{}
|
|
|
|
defer(const defer &) = delete;
|
|
~defer() noexcept;
|
|
};
|
|
|
|
/// Asserts that unwind is occurring without any exception. This allows some
|
|
/// section of code, for example, the latter half of a function, to assert that
|
|
/// it is not throwing and disrupting the other half. This is useful when no
|
|
/// exception is expected thus placing other guarantees should not be required
|
|
/// if this guarantee is met.
|
|
///
|
|
struct ircd::util::unwind::nominal::assertion
|
|
{
|
|
~assertion() noexcept
|
|
{
|
|
assert(likely(!std::uncaught_exceptions()));
|
|
}
|
|
};
|
|
|
|
/// Complements exceptional::assertion. This triggers an assertion when
|
|
/// unwinding WITHOUT an exception.
|
|
///
|
|
struct ircd::util::unwind::exceptional::assertion
|
|
{
|
|
~assertion() noexcept
|
|
{
|
|
assert(likely(std::uncaught_exceptions()));
|
|
}
|
|
};
|