mirror of
https://github.com/ecency/ecency-mobile.git
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289 lines
8.8 KiB
C++
289 lines
8.8 KiB
C++
/*
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* Copyright 2011-present Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <cstddef>
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#include <cstdlib>
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#include <functional>
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#include <new>
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#include <type_traits>
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#include <utility>
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#include <folly/Portability.h>
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#include <folly/Preprocessor.h>
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#include <folly/Utility.h>
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#include <folly/lang/UncaughtExceptions.h>
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namespace folly {
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namespace detail {
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class ScopeGuardImplBase {
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public:
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void dismiss() noexcept {
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dismissed_ = true;
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}
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protected:
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ScopeGuardImplBase() noexcept : dismissed_(false) {}
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static void warnAboutToCrash() noexcept;
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static ScopeGuardImplBase makeEmptyScopeGuard() noexcept {
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return ScopeGuardImplBase{};
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}
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template <typename T>
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static const T& asConst(const T& t) noexcept {
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return t;
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}
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bool dismissed_;
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};
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template <typename FunctionType, bool InvokeNoexcept>
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class ScopeGuardImpl : public ScopeGuardImplBase {
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public:
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explicit ScopeGuardImpl(FunctionType& fn) noexcept(
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std::is_nothrow_copy_constructible<FunctionType>::value)
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: ScopeGuardImpl(
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asConst(fn),
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makeFailsafe(
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std::is_nothrow_copy_constructible<FunctionType>{},
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&fn)) {}
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explicit ScopeGuardImpl(const FunctionType& fn) noexcept(
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std::is_nothrow_copy_constructible<FunctionType>::value)
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: ScopeGuardImpl(
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fn,
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makeFailsafe(
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std::is_nothrow_copy_constructible<FunctionType>{},
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&fn)) {}
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explicit ScopeGuardImpl(FunctionType&& fn) noexcept(
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std::is_nothrow_move_constructible<FunctionType>::value)
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: ScopeGuardImpl(
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std::move_if_noexcept(fn),
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makeFailsafe(
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std::is_nothrow_move_constructible<FunctionType>{},
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&fn)) {}
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ScopeGuardImpl(ScopeGuardImpl&& other) noexcept(
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std::is_nothrow_move_constructible<FunctionType>::value)
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: function_(std::move_if_noexcept(other.function_)) {
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// If the above line attempts a copy and the copy throws, other is
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// left owning the cleanup action and will execute it (or not) depending
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// on the value of other.dismissed_. The following lines only execute
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// if the move/copy succeeded, in which case *this assumes ownership of
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// the cleanup action and dismisses other.
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dismissed_ = exchange(other.dismissed_, true);
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}
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~ScopeGuardImpl() noexcept(InvokeNoexcept) {
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if (!dismissed_) {
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execute();
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}
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}
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private:
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static ScopeGuardImplBase makeFailsafe(std::true_type, const void*) noexcept {
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return makeEmptyScopeGuard();
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}
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template <typename Fn>
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static auto makeFailsafe(std::false_type, Fn* fn) noexcept
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-> ScopeGuardImpl<decltype(std::ref(*fn)), InvokeNoexcept> {
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return ScopeGuardImpl<decltype(std::ref(*fn)), InvokeNoexcept>{
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std::ref(*fn)};
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}
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template <typename Fn>
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explicit ScopeGuardImpl(Fn&& fn, ScopeGuardImplBase&& failsafe)
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: ScopeGuardImplBase{}, function_(std::forward<Fn>(fn)) {
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failsafe.dismiss();
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}
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void* operator new(std::size_t) = delete;
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void execute() noexcept(InvokeNoexcept) {
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if (InvokeNoexcept) {
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try {
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function_();
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} catch (...) {
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warnAboutToCrash();
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std::terminate();
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}
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} else {
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function_();
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}
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}
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FunctionType function_;
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};
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template <typename F, bool INE>
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using ScopeGuardImplDecay = ScopeGuardImpl<typename std::decay<F>::type, INE>;
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} // namespace detail
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/**
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* ScopeGuard is a general implementation of the "Initialization is
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* Resource Acquisition" idiom. Basically, it guarantees that a function
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* is executed upon leaving the currrent scope unless otherwise told.
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*
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* The makeGuard() function is used to create a new ScopeGuard object.
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* It can be instantiated with a lambda function, a std::function<void()>,
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* a functor, or a void(*)() function pointer.
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*
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*
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* Usage example: Add a friend to memory if and only if it is also added
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* to the db.
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*
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* void User::addFriend(User& newFriend) {
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* // add the friend to memory
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* friends_.push_back(&newFriend);
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*
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* // If the db insertion that follows fails, we should
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* // remove it from memory.
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* auto guard = makeGuard([&] { friends_.pop_back(); });
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*
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* // this will throw an exception upon error, which
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* // makes the ScopeGuard execute UserCont::pop_back()
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* // once the Guard's destructor is called.
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* db_->addFriend(GetName(), newFriend.GetName());
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*
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* // an exception was not thrown, so don't execute
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* // the Guard.
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* guard.dismiss();
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* }
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*
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* Examine ScopeGuardTest.cpp for some more sample usage.
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*
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* Stolen from:
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* Andrei's and Petru Marginean's CUJ article:
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* http://drdobbs.com/184403758
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* and the loki library:
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* http://loki-lib.sourceforge.net/index.php?n=Idioms.ScopeGuardPointer
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* and triendl.kj article:
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* http://www.codeproject.com/KB/cpp/scope_guard.aspx
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*/
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template <typename F>
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detail::ScopeGuardImplDecay<F, true> makeGuard(F&& f) noexcept(
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noexcept(detail::ScopeGuardImplDecay<F, true>(static_cast<F&&>(f)))) {
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return detail::ScopeGuardImplDecay<F, true>(static_cast<F&&>(f));
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}
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namespace detail {
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#if defined(FOLLY_EXCEPTION_COUNT_USE_CXA_GET_GLOBALS) || \
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defined(FOLLY_EXCEPTION_COUNT_USE_GETPTD) || \
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defined(FOLLY_EXCEPTION_COUNT_USE_STD)
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/**
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* ScopeGuard used for executing a function when leaving the current scope
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* depending on the presence of a new uncaught exception.
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*
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* If the executeOnException template parameter is true, the function is
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* executed if a new uncaught exception is present at the end of the scope.
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* If the parameter is false, then the function is executed if no new uncaught
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* exceptions are present at the end of the scope.
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*
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* Used to implement SCOPE_FAIL and SCOPE_SUCCESS below.
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*/
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template <typename FunctionType, bool ExecuteOnException>
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class ScopeGuardForNewException {
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public:
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explicit ScopeGuardForNewException(const FunctionType& fn) : guard_(fn) {}
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explicit ScopeGuardForNewException(FunctionType&& fn)
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: guard_(std::move(fn)) {}
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ScopeGuardForNewException(ScopeGuardForNewException&& other) = default;
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~ScopeGuardForNewException() noexcept(ExecuteOnException) {
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if (ExecuteOnException != (exceptionCounter_ < uncaught_exceptions())) {
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guard_.dismiss();
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}
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}
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private:
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void* operator new(std::size_t) = delete;
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void operator delete(void*) = delete;
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ScopeGuardImpl<FunctionType, ExecuteOnException> guard_;
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int exceptionCounter_{uncaught_exceptions()};
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};
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/**
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* Internal use for the macro SCOPE_FAIL below
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*/
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enum class ScopeGuardOnFail {};
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template <typename FunctionType>
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ScopeGuardForNewException<typename std::decay<FunctionType>::type, true>
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operator+(detail::ScopeGuardOnFail, FunctionType&& fn) {
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return ScopeGuardForNewException<
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typename std::decay<FunctionType>::type,
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true>(std::forward<FunctionType>(fn));
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}
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/**
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* Internal use for the macro SCOPE_SUCCESS below
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*/
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enum class ScopeGuardOnSuccess {};
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template <typename FunctionType>
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ScopeGuardForNewException<typename std::decay<FunctionType>::type, false>
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operator+(ScopeGuardOnSuccess, FunctionType&& fn) {
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return ScopeGuardForNewException<
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typename std::decay<FunctionType>::type,
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false>(std::forward<FunctionType>(fn));
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}
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#endif // native uncaught_exception() supported
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/**
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* Internal use for the macro SCOPE_EXIT below
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*/
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enum class ScopeGuardOnExit {};
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template <typename FunctionType>
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ScopeGuardImpl<typename std::decay<FunctionType>::type, true> operator+(
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detail::ScopeGuardOnExit,
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FunctionType&& fn) {
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return ScopeGuardImpl<typename std::decay<FunctionType>::type, true>(
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std::forward<FunctionType>(fn));
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}
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} // namespace detail
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} // namespace folly
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#define SCOPE_EXIT \
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auto FB_ANONYMOUS_VARIABLE(SCOPE_EXIT_STATE) = \
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::folly::detail::ScopeGuardOnExit() + [&]() noexcept
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#if defined(FOLLY_EXCEPTION_COUNT_USE_CXA_GET_GLOBALS) || \
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defined(FOLLY_EXCEPTION_COUNT_USE_GETPTD) || \
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defined(FOLLY_EXCEPTION_COUNT_USE_STD)
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#define SCOPE_FAIL \
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auto FB_ANONYMOUS_VARIABLE(SCOPE_FAIL_STATE) = \
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::folly::detail::ScopeGuardOnFail() + [&]() noexcept
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#define SCOPE_SUCCESS \
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auto FB_ANONYMOUS_VARIABLE(SCOPE_SUCCESS_STATE) = \
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::folly::detail::ScopeGuardOnSuccess() + [&]()
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#endif // native uncaught_exception() supported
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