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403 lines
14 KiB
403 lines
14 KiB
/*
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* Copyright (C) 2018 The Android Open Source Project
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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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#ifndef LIBTEXTCLASSIFIER_UTILS_BASE_STATUSOR_H_
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#define LIBTEXTCLASSIFIER_UTILS_BASE_STATUSOR_H_
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#include <type_traits>
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#include <utility>
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#include "utils/base/logging.h"
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#include "utils/base/macros.h"
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#include "utils/base/status.h"
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namespace libtextclassifier3 {
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// A StatusOr holds a Status (in the case of an error), or a value T.
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template <typename T>
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class StatusOr {
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public:
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// Has status UNKNOWN.
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inline StatusOr();
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// Builds from a non-OK status. Crashes if an OK status is specified.
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inline StatusOr(const Status& status); // NOLINT
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// Builds from the specified value.
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inline StatusOr(const T& value); // NOLINT
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inline StatusOr(T&& value); // NOLINT
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// Copy constructor.
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inline StatusOr(const StatusOr& other);
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// Move constructor.
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inline StatusOr(StatusOr&& other);
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// Conversion copy constructor, T must be copy constructible from U.
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template <typename U,
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std::enable_if_t<
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std::conjunction<std::negation<std::is_same<T, U>>,
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std::is_constructible<T, const U&>,
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std::is_convertible<const U&, T>>::value,
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int> = 0>
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inline StatusOr(const StatusOr<U>& other); // NOLINT
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// Conversion move constructor, T must by move constructible from U.
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template <
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typename U,
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std::enable_if_t<std::conjunction<std::negation<std::is_same<T, U>>,
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std::is_constructible<T, U&&>,
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std::is_convertible<U&&, T>>::value,
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int> = 0>
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inline StatusOr(StatusOr<U>&& other); // NOLINT
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// Value conversion copy constructor, T must by copy constructible from U.
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template <typename U,
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std::enable_if_t<
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std::conjunction<std::negation<std::is_same<T, U>>,
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std::is_constructible<T, const U&>,
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std::is_convertible<const U&, T>>::value,
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int> = 0>
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inline StatusOr(const U& value); // NOLINT
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// Value conversion move constructor, T must by move constructible from U.
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template <
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typename U,
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std::enable_if_t<std::conjunction<std::negation<std::is_same<T, U>>,
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std::is_constructible<T, U&&>,
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std::is_convertible<U&&, T>>::value,
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int> = 0>
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inline StatusOr(U&& value); // NOLINT
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// Assignment operator.
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inline StatusOr& operator=(const StatusOr& other);
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inline StatusOr& operator=(StatusOr&& other);
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// Conversion assignment operator, T must be assignable from U
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template <typename U>
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inline StatusOr& operator=(const StatusOr<U>& other);
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template <typename U>
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inline StatusOr& operator=(StatusOr<U>&& other);
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inline ~StatusOr();
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// Accessors.
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inline const Status& status() const& { return status_; }
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inline Status status() && { return std::move(status_); }
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// Shorthand for status().ok().
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inline bool ok() const { return status_.ok(); }
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// Returns value or crashes if ok() is false.
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inline const T& ValueOrDie() const& {
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if (!ok()) {
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TC3_LOG(FATAL) << "Attempting to fetch value of non-OK StatusOr: "
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<< status();
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exit(1);
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}
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return value_;
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}
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inline T& ValueOrDie() & {
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if (!ok()) {
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TC3_LOG(FATAL) << "Attempting to fetch value of non-OK StatusOr: "
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<< status();
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exit(1);
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}
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return value_;
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}
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inline const T&& ValueOrDie() const&& {
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if (!ok()) {
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TC3_LOG(FATAL) << "Attempting to fetch value of non-OK StatusOr: "
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<< status();
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exit(1);
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}
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return std::move(value_);
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}
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inline T&& ValueOrDie() && {
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if (!ok()) {
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TC3_LOG(FATAL) << "Attempting to fetch value of non-OK StatusOr: "
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<< status();
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exit(1);
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}
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return std::move(value_);
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}
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template <typename U>
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friend class StatusOr;
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private:
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void Clear() {
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if (ok()) {
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value_.~T();
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}
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}
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// Construct the value through placement new with the passed argument.
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template <typename... Arg>
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void MakeValue(Arg&&... arg) {
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new (&value_) T(std::forward<Arg>(arg)...);
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}
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// Creates a valid instance of type T constructed with U and assigns it to
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// value_. Handles how to properly assign to value_ if value_ was never
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// actually initialized (if this is currently non-OK).
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template <typename U>
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void AssignValue(U&& value) {
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if (ok()) {
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value_ = std::forward<U>(value);
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} else {
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MakeValue(std::forward<U>(value));
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status_ = Status::OK;
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}
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}
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// Creates a status constructed with U and assigns it to status_. It also
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// properly destroys value_ if this is OK and value_ represents a valid
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// instance of T.
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template <typename U>
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void AssignStatus(U&& v) {
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Clear();
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status_ = static_cast<Status>(std::forward<U>(v));
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}
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Status status_;
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// The members of unions do not require initialization and are not destructed
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// unless specifically called. This allows us to construct instances of
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// StatusOr with only error statuses where T is not default constructible.
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union {
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// value_ is active iff status_.ok()==true
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// WARNING: The destructor of value_ is called ONLY if status_ is OK.
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T value_;
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};
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};
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// Implementation.
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template <typename T>
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inline StatusOr<T>::StatusOr() : status_(StatusCode::UNKNOWN, "") {}
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template <typename T>
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inline StatusOr<T>::StatusOr(const Status& status) : status_(status) {
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if (status.ok()) {
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TC3_LOG(FATAL) << "OkStatus() is not a valid argument to StatusOr";
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exit(1);
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}
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}
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template <typename T>
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inline StatusOr<T>::StatusOr(const T& value) : value_(value) {}
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template <typename T>
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inline StatusOr<T>::StatusOr(T&& value) : value_(std::move(value)) {}
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template <typename T>
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inline StatusOr<T>::StatusOr(const StatusOr& other)
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: status_(other.status_), value_(other.value_) {}
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template <typename T>
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inline StatusOr<T>::StatusOr(StatusOr&& other)
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: status_(other.status_), value_(std::move(other.value_)) {}
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template <typename T>
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template <
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typename U,
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std::enable_if_t<std::conjunction<std::negation<std::is_same<T, U>>,
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std::is_constructible<T, const U&>,
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std::is_convertible<const U&, T>>::value,
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int>>
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inline StatusOr<T>::StatusOr(const StatusOr<U>& other)
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: status_(other.status_), value_(other.value_) {}
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template <typename T>
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template <typename U,
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std::enable_if_t<std::conjunction<std::negation<std::is_same<T, U>>,
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std::is_constructible<T, U&&>,
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std::is_convertible<U&&, T>>::value,
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int>>
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inline StatusOr<T>::StatusOr(StatusOr<U>&& other)
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: status_(other.status_), value_(std::move(other.value_)) {}
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template <typename T>
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template <
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typename U,
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std::enable_if_t<std::conjunction<std::negation<std::is_same<T, U>>,
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std::is_constructible<T, const U&>,
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std::is_convertible<const U&, T>>::value,
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int>>
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inline StatusOr<T>::StatusOr(const U& value) : StatusOr(T(value)) {}
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template <typename T>
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template <typename U,
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std::enable_if_t<std::conjunction<std::negation<std::is_same<T, U>>,
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std::is_constructible<T, U&&>,
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std::is_convertible<U&&, T>>::value,
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int>>
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inline StatusOr<T>::StatusOr(U&& value) : StatusOr(T(std::forward<U>(value))) {}
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template <typename T>
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inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr& other) {
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if (other.ok()) {
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AssignValue(other.value_);
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} else {
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AssignStatus(other.status_);
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}
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return *this;
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}
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template <typename T>
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inline StatusOr<T>& StatusOr<T>::operator=(StatusOr&& other) {
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if (other.ok()) {
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AssignValue(std::move(other.value_));
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} else {
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AssignStatus(std::move(other.status_));
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}
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return *this;
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}
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template <typename T>
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inline StatusOr<T>::~StatusOr() {
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Clear();
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}
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template <typename T>
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template <typename U>
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inline StatusOr<T>& StatusOr<T>::operator=(const StatusOr<U>& other) {
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if (other.ok()) {
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AssignValue(other.value_);
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} else {
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AssignStatus(other.status_);
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}
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return *this;
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}
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template <typename T>
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template <typename U>
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inline StatusOr<T>& StatusOr<T>::operator=(StatusOr<U>&& other) {
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if (other.ok()) {
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AssignValue(std::move(other.value_));
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} else {
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AssignStatus(std::move(other.status_));
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}
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return *this;
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}
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} // namespace libtextclassifier3
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#define TC3_ASSIGN_OR_RETURN(...) \
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TC_STATUS_MACROS_IMPL_GET_VARIADIC_( \
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(__VA_ARGS__, TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_3_, \
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TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_2_)) \
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(__VA_ARGS__)
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#define TC3_ASSIGN_OR_RETURN_NULL(lhs, rexpr) \
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TC3_ASSIGN_OR_RETURN(lhs, rexpr, nullptr)
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#define TC3_ASSIGN_OR_RETURN_FALSE(lhs, rexpr) \
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TC3_ASSIGN_OR_RETURN(lhs, rexpr, false)
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#define TC3_ASSIGN_OR_RETURN_0(...) \
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TC_STATUS_MACROS_IMPL_GET_VARIADIC_( \
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(__VA_ARGS__, TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_0_3_, \
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TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_0_2_)) \
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(__VA_ARGS__)
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#define TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_0_2_(lhs, rexpr) \
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TC3_ASSIGN_OR_RETURN(lhs, rexpr, 0)
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#define TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_0_3_(lhs, rexpr, \
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log_expression) \
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TC3_ASSIGN_OR_RETURN(lhs, rexpr, (log_expression, 0))
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// =================================================================
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// == Implementation details, do not rely on anything below here. ==
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// =================================================================
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// Some builds do not support C++14 fully yet, using C++11 constexpr technique.
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constexpr bool HasPossiblyConditionalOperator(const char* lhs, int index) {
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return (index == -1 ? false
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: (lhs[index] == '?'
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? true
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: HasPossiblyConditionalOperator(lhs, index - 1)));
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}
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// MSVC incorrectly expands variadic macros, splice together a macro call to
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// work around the bug.
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#define TC_STATUS_MACROS_IMPL_GET_VARIADIC_HELPER_(_1, _2, _3, NAME, ...) NAME
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#define TC_STATUS_MACROS_IMPL_GET_VARIADIC_(args) \
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TC_STATUS_MACROS_IMPL_GET_VARIADIC_HELPER_ args
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#define TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_2_(lhs, rexpr) \
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TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_3_(lhs, rexpr, _)
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#define TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_3_(lhs, rexpr, \
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error_expression) \
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TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_( \
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TC_STATUS_MACROS_IMPL_CONCAT_(_status_or_value, __COUNTER__), lhs, \
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rexpr, error_expression)
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#define TC_STATUS_MACROS_IMPL_ASSIGN_OR_RETURN_(statusor, lhs, rexpr, \
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error_expression) \
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auto statusor = (rexpr); \
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if (!statusor.ok()) { \
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::libtextclassifier3::Status _(std::move(statusor).status()); \
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(void)_; /* error_expression is allowed to not use this variable */ \
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return (error_expression); \
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} \
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{ \
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static_assert(#lhs[0] != '(' || #lhs[sizeof(#lhs) - 2] != ')' || \
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!HasPossiblyConditionalOperator(#lhs, sizeof(#lhs) - 2), \
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"Identified potential conditional operator, consider not " \
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"using ASSIGN_OR_RETURN"); \
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} \
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TC_STATUS_MACROS_IMPL_UNPARENTHESIZE_IF_PARENTHESIZED(lhs) = \
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std::move(statusor).ValueOrDie()
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// Internal helpers for macro expansion.
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#define TC_STATUS_MACROS_IMPL_EAT(...)
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#define TC_STATUS_MACROS_IMPL_REM(...) __VA_ARGS__
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#define TC_STATUS_MACROS_IMPL_EMPTY()
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// Internal helpers for emptyness arguments check.
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#define TC_STATUS_MACROS_IMPL_IS_EMPTY_INNER(...) \
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TC_STATUS_MACROS_IMPL_IS_EMPTY_INNER_I(__VA_ARGS__, 0, 1)
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#define TC_STATUS_MACROS_IMPL_IS_EMPTY_INNER_I(e0, e1, is_empty, ...) is_empty
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#define TC_STATUS_MACROS_IMPL_IS_EMPTY(...) \
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TC_STATUS_MACROS_IMPL_IS_EMPTY_I(__VA_ARGS__)
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#define TC_STATUS_MACROS_IMPL_IS_EMPTY_I(...) \
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TC_STATUS_MACROS_IMPL_IS_EMPTY_INNER(_, ##__VA_ARGS__)
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// Internal helpers for if statement.
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#define TC_STATUS_MACROS_IMPL_IF_1(_Then, _Else) _Then
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#define TC_STATUS_MACROS_IMPL_IF_0(_Then, _Else) _Else
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#define TC_STATUS_MACROS_IMPL_IF(_Cond, _Then, _Else) \
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TC_STATUS_MACROS_IMPL_CONCAT_(TC_STATUS_MACROS_IMPL_IF_, _Cond)(_Then, _Else)
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// Expands to 1 if the input is parenthesized. Otherwise expands to 0.
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#define TC_STATUS_MACROS_IMPL_IS_PARENTHESIZED(...) \
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TC_STATUS_MACROS_IMPL_IS_EMPTY(TC_STATUS_MACROS_IMPL_EAT __VA_ARGS__)
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// If the input is parenthesized, removes the parentheses. Otherwise expands to
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// the input unchanged.
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#define TC_STATUS_MACROS_IMPL_UNPARENTHESIZE_IF_PARENTHESIZED(...) \
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TC_STATUS_MACROS_IMPL_IF( \
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TC_STATUS_MACROS_IMPL_IS_PARENTHESIZED(__VA_ARGS__), \
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TC_STATUS_MACROS_IMPL_REM, TC_STATUS_MACROS_IMPL_EMPTY()) \
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__VA_ARGS__
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// Internal helper for concatenating macro values.
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#define TC_STATUS_MACROS_IMPL_CONCAT_INNER_(x, y) x##y
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#define TC_STATUS_MACROS_IMPL_CONCAT_(x, y) \
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TC_STATUS_MACROS_IMPL_CONCAT_INNER_(x, y)
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#endif // LIBTEXTCLASSIFIER_UTILS_BASE_STATUSOR_H_
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