98 lines
2.2 KiB
C++
98 lines
2.2 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2019 Danny Robson <danny@nerdcruft.net>
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*/
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#include <exception>
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///////////////////////////////////////////////////////////////////////////////
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namespace cruft {
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class bad_expected_access : public std::exception {
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public:
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char const* what (void) const noexcept override
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{
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return "bad_expected_access";
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}
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};
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template <typename ValueT, typename ErrorT>
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struct expected {
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using value_type = ValueT;
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using error_type = ErrorT;
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expected (ValueT &&_value)
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{
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::new (&m_store.value) ValueT (std::move (_value));
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m_valid = true;
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}
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expected (ErrorT &&_error)
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{
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::new (&m_store.error) ErrorT (std::move (_error));
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}
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~expected ()
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{
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if (m_valid) {
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m_store.value.~ValueT ();
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m_valid = false;
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} else {
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m_store.error.~ErrorT ();
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}
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}
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ValueT&
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value (void)&
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{
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if (!m_valid)
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throw bad_expected_access {};
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return m_store.value;
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}
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ValueT&&
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value (void)&&
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{
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if (!m_valid)
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throw bad_expected_access {};
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return std::move (m_store.value);
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}
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ErrorT&
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error (void)&
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{
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if (m_valid)
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throw bad_expected_access {};
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return m_store.error;
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}
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ErrorT&&
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error (void)&&
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{
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if (m_valid)
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throw bad_expected_access {};
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return std::move (m_store.error);
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}
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ValueT* operator-> (void)& { return &value (); }
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ValueT& operator* (void)& { return value (); }
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operator bool() const noexcept;
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private:
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union storage_t {
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storage_t () {};
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~storage_t () {};
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char defer;
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ValueT value;
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ErrorT error;
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} m_store;
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bool m_valid = false;
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};
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}; |