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+/*
+ 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;
+};
+
+}