guan404ming commented on code in PR #399: URL: https://github.com/apache/tvm-ffi/pull/399#discussion_r2721948756
########## include/tvm/ffi/expected.h: ########## @@ -0,0 +1,239 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +/*! + * \file tvm/ffi/expected.h + * \brief Runtime Expected container type for exception-free error handling. + */ +#ifndef TVM_FFI_EXPECTED_H_ +#define TVM_FFI_EXPECTED_H_ + +#include <tvm/ffi/any.h> +#include <tvm/ffi/error.h> + +#include <type_traits> +#include <utility> + +namespace tvm { +namespace ffi { + +/*! + * \brief Expected<T> provides exception-free error handling for FFI functions. + * + * Expected<T> is similar to Rust's Result<T, Error> or C++23's std::expected. + * It can hold either a success value of type T or an error of type Error. + * + * \tparam T The success type. Must be Any-compatible and cannot be Error. + * + * Usage: + * \code + * Expected<int> divide(int a, int b) { + * if (b == 0) { + * return ExpectedErr(Error("ValueError", "Division by zero")); + * } + * return ExpectedOk(a / b); + * } + * + * Expected<int> result = divide(10, 2); + * if (result.is_ok()) { + * int value = result.value(); + * } else { + * Error err = result.error(); + * } + * \endcode + */ +template <typename T> +class Expected { + public: + static_assert(!std::is_same_v<T, Error>, "Expected<Error> is not allowed. Use Error directly."); + + /*! + * \brief Create an Expected with a success value. + * \param value The success value. + * \return Expected containing the success value. + */ + static Expected Ok(T value) { return Expected(Any(std::move(value))); } + + /*! + * \brief Create an Expected with an error. + * \param error The error value. + * \return Expected containing the error. + */ + static Expected Err(Error error) { return Expected(Any(std::move(error))); } + + /*! + * \brief Check if the Expected contains a success value. + * \return True if contains success value, false if contains error. + * \note Checks for Error first to handle cases where T is a base class of Error. + */ + TVM_FFI_INLINE bool is_ok() const { return !data_.as<Error>().has_value(); } + + /*! + * \brief Check if the Expected contains an error. + * \return True if contains error, false if contains success value. + */ + TVM_FFI_INLINE bool is_err() const { return !is_ok(); } + + /*! + * \brief Alias for is_ok(). + * \return True if contains success value. + */ + TVM_FFI_INLINE bool has_value() const { return is_ok(); } + + /*! \brief Access the success value. Throws the contained error if is_err(). */ + TVM_FFI_INLINE T value() const& { + if (is_err()) throw data_.cast<Error>(); + return data_.cast<T>(); + } + /*! \brief Access the success value (rvalue). Throws the contained error if is_err(). */ + TVM_FFI_INLINE T value() && { + if (is_err()) throw std::move(data_).template cast<Error>(); + return std::move(data_).template cast<T>(); + } + + /*! \brief Access the error. Throws RuntimeError if is_ok(). */ + TVM_FFI_INLINE Error error() const& { + if (!is_err()) TVM_FFI_THROW(RuntimeError) << "Bad expected access: contains value, not error"; + return data_.cast<Error>(); + } + /*! \brief Access the error (rvalue). Throws RuntimeError if is_ok(). */ + TVM_FFI_INLINE Error error() && { + if (!is_err()) TVM_FFI_THROW(RuntimeError) << "Bad expected access: contains value, not error"; + return std::move(data_).template cast<Error>(); + } + + /*! + * \brief Get the success value or a default value. + * \param default_value The value to return if Expected contains an error. + * \return The success value if present, otherwise the default value. + */ + template <typename U = std::remove_cv_t<T>> + TVM_FFI_INLINE T value_or(U&& default_value) const { + if (is_ok()) { + return data_.cast<T>(); + } + return T(std::forward<U>(default_value)); + } + + private: + friend struct TypeTraits<Expected<T>>; + + /*! + * \brief Private constructor from Any. + * \param data The data containing either T or Error. + * \note This constructor is used by TypeTraits for conversion. + */ + explicit Expected(Any data) : data_(std::move(data)) { + TVM_FFI_ICHECK(data_.as<T>().has_value() || data_.as<Error>().has_value()) + << "Expected must contain either T or Error"; + } + + Any data_; // Holds either T or Error +}; + +/*! + * \brief Helper function to create Expected::Ok with type deduction. + * \tparam T The success type (deduced from argument). + * \param value The success value. + * \return Expected<T> containing the success value. + */ +template <typename T> +TVM_FFI_INLINE Expected<T> ExpectedOk(T value) { + return Expected<T>::Ok(std::move(value)); +} + +/*! + * \brief Helper function to create Expected::Err. + * \param error The error value. + * \return Expected<Any> containing the error. + * \note Returns Expected<Any> to allow usage in contexts where T is inferred. + */ +template <typename T = Any> +TVM_FFI_INLINE Expected<T> ExpectedErr(Error error) { + return Expected<T>::Err(std::move(error)); +} + +// TypeTraits specialization for Expected<T> +template <typename T> +inline constexpr bool use_default_type_traits_v<Expected<T>> = false; + +template <typename T> +struct TypeTraits<Expected<T>> : public TypeTraitsBase { + TVM_FFI_INLINE static void CopyToAnyView(const Expected<T>& src, TVMFFIAny* result) { + const TVMFFIAny* src_any = reinterpret_cast<const TVMFFIAny*>(&src.data_); + if (TypeTraits<T>::CheckAnyStrict(src_any)) { + TypeTraits<T>::MoveToAny(TypeTraits<T>::CopyFromAnyViewAfterCheck(src_any), result); Review Comment: Thanks, this is more clearer. -- This is an automated message from the Apache Git Service. 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