157 lines
3.5 KiB
C++
157 lines
3.5 KiB
C++
/*
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** Copyright (C) 2019-2023 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
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**
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** This program is free software; you can redistribute it and/or modify it
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** under the terms of the GNU General Public License as published by the
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** Free Software Foundation; either version 3, or (at your option) any
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** later version.
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**
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** This program is distributed in the hope that it will be useful,
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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** GNU General Public License for more details.
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**
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** You should have received a copy of the GNU General Public License
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** along with this program; if not, write to the Free Software Foundation,
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** Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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**
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*/
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#ifndef MU_RESULT_HH__
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#define MU_RESULT_HH__
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#include <utility>
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#include <type_traits>
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#include <tl/expected.hpp>
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#include "utils/mu-error.hh"
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namespace Mu {
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/**
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* A little Rust-envy...a Result is _either_ some value of type T, _or_ a Mu::Error
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*
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* Note: nothing outside this header uses tl:: directly, and Result only uses
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* the std::expected subset of the API; so once mu requires C++23, this can
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* simply become std::expected (with tl::unexpected -> std::unexpected below).
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*/
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template <typename T> using Result = tl::expected<T, Error>;
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/**
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* Ok() is not typically strictly needed (unlike Err), but imitates Rust's Ok
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* and it helps the reader.
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*
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* @param t the value to return; copied when passed an lvalue, moved when
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* passed an rvalue.
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*
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* @return a success Result<T>
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*/
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template <typename T> [[nodiscard]] Result<std::decay_t<T>>
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Ok(T&& t)
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{
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return std::forward<T>(t);
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}
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/**
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* Implementation of Ok() for void results.
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*
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* @return a success Result<void>
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*/
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[[nodiscard]] inline Result<void>
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Ok()
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{
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return {};
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}
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/**
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* Return an error
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*
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* @param err the error
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*
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* @return error
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*/
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[[nodiscard]] inline tl::unexpected<Error>
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Err(Error&& err)
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{
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return tl::unexpected(std::move(err));
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}
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[[nodiscard]] inline tl::unexpected<Error>
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Err(const Error& err)
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{
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return tl::unexpected(err);
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}
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/**
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* Get the error from some error Result
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*
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* @param res a Result; must hold an error (checking that is up to the
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* caller)
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*
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* @return the error
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*/
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template<typename T>
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[[nodiscard]] inline tl::unexpected<Error>
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Err(const Result<T>& res)
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{
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return tl::unexpected(res.error());
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}
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template<typename T>
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[[nodiscard]] inline tl::unexpected<Error>
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Err(Result<T>&& res)
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{
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return tl::unexpected(std::move(res.error()));
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}
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/*
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* convenience
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*/
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template <typename ...T>
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[[nodiscard]] tl::unexpected<Error>
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Err(Error::Code code, fmt::format_string<T...> frm, T&&... args)
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{
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return Err(Error{code, frm, std::forward<T>(args)...});
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}
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template <typename ...T>
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[[nodiscard]] tl::unexpected<Error>
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Err(Error::Code code, GError **err, fmt::format_string<T...> frm, T&&... args)
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{
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return Err(Error{code, err, frm, std::forward<T>(args)...});
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}
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/**
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* Get the value from a Result, or throw its error
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*
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* @param res a Result
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*
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* @return the value (moved out of @p res)
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*/
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template<typename T> T
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unwrap(Result<T>&& res)
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{
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if (!!res)
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return std::move(res.value());
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else
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throw std::move(res.error());
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}
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/**
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* Assert that some result has a value (for unit tests)
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*
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* @param R some result
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*/
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#define assert_valid_result(R) do { \
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auto&& res__ = R; \
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if(!res__) { \
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mu_printerrln("{}:{}: error-result: {}", \
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__FILE__, __LINE__, \
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(res__).error().what()); \
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g_assert_true(!!res__); \
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} \
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} while(0)
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}// namespace Mu
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#endif /* MU_RESULT_HH__ */
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