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66f7b27121
For issue #7557 and #7556 Note: this change the API of the VFS plugin, so the VFS plugin needs small adaptations
159 lines
3.3 KiB
C++
159 lines
3.3 KiB
C++
/*
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* Copyright (C) by Olivier Goffart <ogoffart@woboq.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*/
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#pragma once
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#include "asserts.h"
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namespace OCC {
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/**
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* A Result of type T, or an Error
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*/
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template <typename T, typename Error>
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class Result
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{
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union {
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T _result;
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Error _error;
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};
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bool _isError;
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public:
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Result(T value)
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: _result(std::move(value))
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, _isError(false)
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{
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}
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// TODO: This doesn't work if T and Error are too similar
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Result(Error error)
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: _error(std::move(error))
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, _isError(true)
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{
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}
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Result(Result &&other)
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: _isError(other._isError)
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{
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if (_isError) {
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new (&_error) Error(std::move(other._error));
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} else {
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new (&_result) T(std::move(other._result));
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}
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}
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Result(const Result &other)
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: _isError(other._isError)
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{
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if (_isError) {
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new (&_error) Error(other._error);
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} else {
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new (&_result) T(other._result);
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}
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}
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Result &operator=(Result &&other)
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{
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if (&other != this) {
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_isError = other._isError;
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if (_isError) {
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new (&_error) Error(std::move(other._error));
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} else {
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new (&_result) T(std::move(other._result));
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}
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}
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return *this;
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}
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Result &operator=(const Result &other)
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{
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if (&other != this) {
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_isError = other._isError;
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if (_isError) {
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new (&_error) Error(other._error);
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} else {
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new (&_result) T(other._result);
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}
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}
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return *this;
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}
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~Result()
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{
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if (_isError)
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_error.~Error();
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else
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_result.~T();
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}
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explicit operator bool() const { return !_isError; }
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const T &operator*() const &
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{
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ASSERT(!_isError);
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return _result;
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}
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T operator*() &&
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{
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ASSERT(!_isError);
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return std::move(_result);
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}
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const T *operator->() const
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{
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ASSERT(!_isError);
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return &_result;
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}
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const Error &error() const &
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{
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ASSERT(_isError);
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return _error;
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}
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Error error() &&
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{
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ASSERT(_isError);
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return std::move(_error);
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}
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};
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namespace detail {
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struct NoResultData{};
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}
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template <typename Error>
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class Result<void, Error> : public Result<detail::NoResultData, Error>
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{
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public:
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using Result<detail::NoResultData, Error>::Result;
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Result() : Result(detail::NoResultData{}) {}
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};
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namespace detail {
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struct OptionalNoErrorData{};
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}
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template <typename T>
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class Optional : public Result<T, detail::OptionalNoErrorData>
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{
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public:
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using Result<T, detail::OptionalNoErrorData>::Result;
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Optional()
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: Optional(detail::OptionalNoErrorData{})
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{
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}
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};
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} // namespace OCC
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