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/*
Copyright (C) 2006 - 2015 Evan Teran
evan.teran@gmail.com
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef STATUS_H_20160803_
#define STATUS_H_20160803_
#include "API.h"
#include <QString>
#include <boost/variant.hpp>
#include <type_traits>
class EDB_EXPORT Status {
public:
enum OkType { Ok };
public:
Status(OkType) {
}
explicit Status(const QString &message)
: error_(message) {
}
Status(const Status &) = default;
Status &operator=(const Status &) = default;
Status(Status &&) = default;
Status &operator=(Status &&) = default;
public:
bool success() const { return error_.isEmpty(); }
bool failure() const { return !success(); }
explicit operator bool() const { return success(); }
QString error() const { return error_; }
private:
QString error_;
};
template <class E>
class Unexpected {
template <class U, class Y>
friend class Expected;
template <class U, class Y>
friend class Result;
template <class U>
friend Unexpected<typename std::decay<U>::type> make_unexpected(U &&);
public:
Unexpected(const Unexpected &) = default;
Unexpected &operator=(const Unexpected &) = default;
Unexpected(Unexpected &&) = default;
Unexpected &operator=(Unexpected &&) = default;
private:
template <class U>
Unexpected(U &&error)
: error_(std::forward<U>(error)) {
}
private:
E error_;
};
template <class T, class E>
class Result {
public:
template <class U, class = typename std::enable_if<std::is_convertible<U, T>::value>::type>
Result(U &&value)
: value_(std::forward<U>(value)) {
}
Result(const Unexpected<E> &value)
: value_(value) {
}
Result(Unexpected<E> &&value)
: value_(std::move(value)) {
}
Result(const Result &) = default;
Result &operator=(const Result &) = default;
Result(Result &&) = default;
Result &operator=(Result &&) = default;
public:
const T *operator->() const {
Q_ASSERT(succeeded());
return &boost::get<T>(value_);
}
const T &operator*() const { return value(); }
bool succeeded() const { return value_.which() == 0; }
bool failed() const { return value_.which() == 1; }
explicit operator bool() const { return succeeded(); }
bool operator!() const { return failed(); }
const E &error() const {
Q_ASSERT(failed());
return boost::get<Unexpected<E>>(value_).error_;
}
const T &value() const {
Q_ASSERT(succeeded());
return boost::get<T>(value_);
}
private:
boost::variant<T, Unexpected<E>> value_;
};
template <class E>
class Result<void, E> {
public:
Result() {
}
Result(const Unexpected<E> &value)
: value_(value) {
}
Result(Unexpected<E> &&value)
: value_(std::move(value)) {
}
Result(const Result &) = default;
Result &operator=(const Result &) = default;
Result(Result &&) = default;
Result &operator=(Result &&) = default;
public:
bool succeeded() const { return value_.which() == 0; }
bool failed() const { return value_.which() == 1; }
explicit operator bool() const { return succeeded(); }
bool operator!() const { return failed(); }
const E &error() const {
Q_ASSERT(failed());
return boost::get<Unexpected<E>>(value_).error_;
}
private:
boost::variant<boost::blank, Unexpected<E>> value_;
};
template <class E>
Unexpected<typename std::decay<E>::type> make_unexpected(E &&e) {
return Unexpected<typename std::decay<E>::type>(std::forward<E>(e));
}
#endif
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