327 lines
8.3 KiB
C++
327 lines
8.3 KiB
C++
/*
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* Copyright 2014-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 <folly/Utility.h>
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#include <folly/functional/Invoke.h>
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#include <stdexcept>
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#include <tuple>
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namespace folly {
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template <class T>
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Try<T>::Try(Try<T>&& t) noexcept(std::is_nothrow_move_constructible<T>::value)
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: contains_(t.contains_) {
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if (contains_ == Contains::VALUE) {
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new (&value_) T(std::move(t.value_));
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} else if (contains_ == Contains::EXCEPTION) {
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new (&e_) exception_wrapper(std::move(t.e_));
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}
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}
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template <class T>
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template <class T2>
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Try<T>::Try(typename std::enable_if<
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std::is_same<Unit, T2>::value,
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Try<void> const&>::type t) noexcept
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: contains_(Contains::NOTHING) {
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if (t.hasValue()) {
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contains_ = Contains::VALUE;
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new (&value_) T();
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} else if (t.hasException()) {
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contains_ = Contains::EXCEPTION;
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new (&e_) exception_wrapper(t.exception());
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}
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}
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template <class T>
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Try<T>& Try<T>::operator=(Try<T>&& t) noexcept(
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std::is_nothrow_move_constructible<T>::value) {
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if (this == &t) {
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return *this;
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}
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destroy();
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if (t.contains_ == Contains::VALUE) {
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new (&value_) T(std::move(t.value_));
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} else if (t.contains_ == Contains::EXCEPTION) {
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new (&e_) exception_wrapper(std::move(t.e_));
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}
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contains_ = t.contains_;
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return *this;
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}
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template <class T>
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Try<T>::Try(const Try<T>& t) noexcept(
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std::is_nothrow_copy_constructible<T>::value) {
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static_assert(
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std::is_copy_constructible<T>::value,
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"T must be copyable for Try<T> to be copyable");
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contains_ = t.contains_;
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if (contains_ == Contains::VALUE) {
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new (&value_) T(t.value_);
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} else if (contains_ == Contains::EXCEPTION) {
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new (&e_) exception_wrapper(t.e_);
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}
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}
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template <class T>
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Try<T>& Try<T>::operator=(const Try<T>& t) noexcept(
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std::is_nothrow_copy_constructible<T>::value) {
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static_assert(
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std::is_copy_constructible<T>::value,
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"T must be copyable for Try<T> to be copyable");
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if (this == &t) {
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return *this;
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}
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destroy();
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if (t.contains_ == Contains::VALUE) {
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new (&value_) T(t.value_);
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} else if (t.contains_ == Contains::EXCEPTION) {
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new (&e_) exception_wrapper(t.e_);
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}
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contains_ = t.contains_;
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return *this;
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}
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template <class T>
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Try<T>::~Try() {
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if (LIKELY(contains_ == Contains::VALUE)) {
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value_.~T();
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} else if (UNLIKELY(contains_ == Contains::EXCEPTION)) {
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e_.~exception_wrapper();
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}
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}
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template <typename T>
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template <typename... Args>
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T& Try<T>::emplace(Args&&... args) noexcept(
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std::is_nothrow_constructible<T, Args&&...>::value) {
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this->destroy();
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new (&value_) T(static_cast<Args&&>(args)...);
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contains_ = Contains::VALUE;
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return value_;
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}
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template <typename T>
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template <typename... Args>
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exception_wrapper& Try<T>::emplaceException(Args&&... args) noexcept(
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std::is_nothrow_constructible<exception_wrapper, Args&&...>::value) {
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this->destroy();
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new (&e_) exception_wrapper(static_cast<Args&&>(args)...);
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contains_ = Contains::EXCEPTION;
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return e_;
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}
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template <class T>
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T& Try<T>::value() & {
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throwIfFailed();
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return value_;
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}
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template <class T>
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T&& Try<T>::value() && {
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throwIfFailed();
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return std::move(value_);
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}
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template <class T>
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const T& Try<T>::value() const& {
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throwIfFailed();
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return value_;
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}
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template <class T>
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const T&& Try<T>::value() const&& {
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throwIfFailed();
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return std::move(value_);
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}
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template <class T>
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void Try<T>::throwIfFailed() const {
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switch (contains_) {
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case Contains::VALUE:
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return;
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case Contains::EXCEPTION:
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e_.throw_exception();
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default:
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throw_exception<UsingUninitializedTry>();
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}
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}
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template <class T>
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void Try<T>::destroy() noexcept {
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auto oldContains = folly::exchange(contains_, Contains::NOTHING);
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if (LIKELY(oldContains == Contains::VALUE)) {
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value_.~T();
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} else if (UNLIKELY(oldContains == Contains::EXCEPTION)) {
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e_.~exception_wrapper();
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}
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}
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Try<void>& Try<void>::operator=(const Try<void>& t) noexcept {
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if (t.hasException()) {
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if (hasException()) {
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e_ = t.e_;
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} else {
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new (&e_) exception_wrapper(t.e_);
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hasValue_ = false;
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}
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} else {
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if (hasException()) {
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e_.~exception_wrapper();
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hasValue_ = true;
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}
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}
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return *this;
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}
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template <typename... Args>
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exception_wrapper& Try<void>::emplaceException(Args&&... args) noexcept(
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std::is_nothrow_constructible<exception_wrapper, Args&&...>::value) {
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if (hasException()) {
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e_.~exception_wrapper();
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}
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new (&e_) exception_wrapper(static_cast<Args&&>(args)...);
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hasValue_ = false;
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return e_;
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}
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void Try<void>::throwIfFailed() const {
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if (hasException()) {
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e_.throw_exception();
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}
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}
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template <typename F>
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typename std::enable_if<
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!std::is_same<invoke_result_t<F>, void>::value,
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Try<invoke_result_t<F>>>::type
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makeTryWith(F&& f) {
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using ResultType = invoke_result_t<F>;
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try {
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return Try<ResultType>(f());
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} catch (std::exception& e) {
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return Try<ResultType>(exception_wrapper(std::current_exception(), e));
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} catch (...) {
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return Try<ResultType>(exception_wrapper(std::current_exception()));
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}
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}
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template <typename F>
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typename std::
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enable_if<std::is_same<invoke_result_t<F>, void>::value, Try<void>>::type
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makeTryWith(F&& f) {
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try {
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f();
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return Try<void>();
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} catch (std::exception& e) {
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return Try<void>(exception_wrapper(std::current_exception(), e));
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} catch (...) {
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return Try<void>(exception_wrapper(std::current_exception()));
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}
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}
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template <typename T, typename... Args>
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T* tryEmplace(Try<T>& t, Args&&... args) noexcept {
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try {
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return std::addressof(t.emplace(static_cast<Args&&>(args)...));
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} catch (const std::exception& ex) {
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t.emplaceException(std::current_exception(), ex);
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return nullptr;
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} catch (...) {
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t.emplaceException(std::current_exception());
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return nullptr;
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}
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}
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void tryEmplace(Try<void>& t) noexcept {
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t.emplace();
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}
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template <typename T, typename Func>
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T* tryEmplaceWith(Try<T>& t, Func&& func) noexcept {
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static_assert(
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std::is_constructible<T, folly::invoke_result_t<Func>>::value,
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"Unable to initialise a value of type T with the result of 'func'");
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try {
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return std::addressof(t.emplace(static_cast<Func&&>(func)()));
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} catch (const std::exception& ex) {
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t.emplaceException(std::current_exception(), ex);
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return nullptr;
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} catch (...) {
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t.emplaceException(std::current_exception());
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return nullptr;
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}
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}
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template <typename Func>
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bool tryEmplaceWith(Try<void>& t, Func&& func) noexcept {
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static_assert(
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std::is_void<folly::invoke_result_t<Func>>::value,
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"Func returns non-void. Cannot be used to emplace Try<void>");
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try {
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static_cast<Func&&>(func)();
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t.emplace();
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return true;
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} catch (const std::exception& ex) {
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t.emplaceException(std::current_exception(), ex);
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return false;
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} catch (...) {
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t.emplaceException(std::current_exception());
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return false;
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}
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}
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namespace try_detail {
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/**
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* Trait that removes the layer of Try abstractions from the passed in type
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*/
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template <typename Type>
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struct RemoveTry;
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template <template <typename...> class TupleType, typename... Types>
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struct RemoveTry<TupleType<folly::Try<Types>...>> {
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using type = TupleType<Types...>;
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};
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template <std::size_t... Indices, typename Tuple>
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auto unwrapTryTupleImpl(folly::index_sequence<Indices...>, Tuple&& instance) {
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using std::get;
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using ReturnType = typename RemoveTry<typename std::decay<Tuple>::type>::type;
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return ReturnType{(get<Indices>(std::forward<Tuple>(instance)).value())...};
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}
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} // namespace try_detail
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template <typename Tuple>
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auto unwrapTryTuple(Tuple&& instance) {
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using TupleDecayed = typename std::decay<Tuple>::type;
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using Seq = folly::make_index_sequence<std::tuple_size<TupleDecayed>::value>;
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return try_detail::unwrapTryTupleImpl(Seq{}, std::forward<Tuple>(instance));
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}
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} // namespace folly
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