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Diffstat (limited to 'libdevcore/Result.h')
-rw-r--r-- | libdevcore/Result.h | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/libdevcore/Result.h b/libdevcore/Result.h new file mode 100644 index 00000000..c1abf380 --- /dev/null +++ b/libdevcore/Result.h @@ -0,0 +1,83 @@ +/* + This file is part of solidity. + + solidity 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 3 of the License, or + (at your option) any later version. + + solidity 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 solidity. If not, see <http://www.gnu.org/licenses/>. +*/ +#pragma once + +#include <string> + +namespace dev +{ + +/// Simple generic result that holds a value and an optional error message. +/// Results can be implicitly converted to and created from the type of +/// the value they hold. +/// +/// Result<bool> check() +/// { +/// if (false) +/// return Result<bool>(false, "Error message.") +/// return true; +/// } +/// +/// A result can also be instantiated using one of the factory methods it provides: +/// +/// using BoolResult = Result<bool>; +/// BoolResult check() +/// { +/// if (false) +/// return BoolResult::failure("Error message"); +/// return BoolResult::success(true); +/// } +/// +/// +struct ResultError { std::string reason; }; + +template <class ResultType> +class Result +{ +public: + /// @{ + /// @name Factory functions + /// Factory functions that provide a verbose way to create a result + static Result<ResultType> Ok(ResultType _value) { return Result(std::move(_value)); } + static Result<ResultType> Err() { return Result(ResultError{std::string()}); } + static Result<ResultType> Err(std::string _error) { return Result(ResultError{std::move(_error)}); } + /// @} + + Result(ResultType _value): m_value(std::move(_value)) {} + Result(ResultError _error): m_error(std::move(_error.reason)) {} + Result(ResultType _value, ResultError _error): m_value(std::move(_value)), m_error(std::move(_error.reason)) {} + + /// @{ + /// @name Wrapper functions + /// Wrapper functions that provide implicit conversions to and explicit retrieval of + /// the value this result holds. + /// If the result is an error, accessing the value results in undefined behaviour. + operator ResultType const&() const { return m_value; } + ResultType& operator*() const { return m_value; } + ResultType const& get() const { return m_value; } + ResultType& get() { return m_value; } + /// @} + + /// @returns the error message (can be empty). + std::string const& err() const { return m_error; } + +private: + ResultType m_value; + std::string m_error; +}; + +} |