wgtmac commented on code in PR #77: URL: https://github.com/apache/iceberg-cpp/pull/77#discussion_r2049989575
########## src/iceberg/struct_like.h: ########## @@ -0,0 +1,278 @@ +/* + * 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. + */ + +#pragma once + +#include <string> +#include <vector> + +#include "iceberg/iceberg_export.h" +#include "iceberg/result.h" +#include "iceberg/type.h" + +namespace iceberg { + +class Scalar; +class StructScalar; +class ArrayScalar; +class ScalarVisitor; +class StructLike; +class StructLikeVisitor; +/** + * @brief Base class representing a generic scalar value. + */ +class ICEBERG_EXPORT Scalar { + public: + virtual ~Scalar() = default; + + /** + * @brief Checks if the scalar represents a null value. + * @return true if the value is null, false otherwise. + */ + virtual bool IsNull() const = 0; + + /** + * @brief Casts the scalar to a specific derived type. + * @tparam T The target derived Scalar type. + * @return Reference to the casted value. + * @throws std::bad_cast if the cast fails. + */ + template <typename T> + const T& as() const { + auto ptr = dynamic_cast<const T*>(this); + if (!ptr) throw std::bad_cast(); + return *ptr; + } + + /** + * @brief Creates a deep copy of the scalar. + * @return A shared pointer to the cloned scalar. + */ + virtual std::shared_ptr<Scalar> clone() const = 0; + + /** + * @brief Accepts a visitor for dispatching based on scalar type. + * @param visitor The visitor to accept. + */ + virtual void accept(ScalarVisitor& visitor) const = 0; +}; + +/** + * @brief Visitor interface for Scalar, supporting type-dispatched operations. + */ +class ICEBERG_EXPORT ScalarVisitor { + public: + virtual ~ScalarVisitor() = default; + + /// Visit methods for primitive types + virtual void visit(int32_t value) = 0; + virtual void visit(int64_t value) = 0; + virtual void visit(float value) = 0; + virtual void visit(double value) = 0; + virtual void visit(bool value) = 0; + virtual void visit(const std::string& value) = 0; + + /** + * @brief Called when visiting a null scalar. + */ + virtual void visitNull() = 0; + + /// Visit methods for complex types + virtual void visitStruct(const StructScalar& value) = 0; + virtual void visitArray(const ArrayScalar& value) = 0; +}; + +/** + * @brief Represents a scalar that holds a primitive value. + * @tparam T The type of the primitive value. + */ +template <typename T> +class ICEBERG_EXPORT PrimitiveScalar : public Scalar { + public: + /** + * @brief Constructs a PrimitiveScalar from an optional value. + * @param value The optional primitive value. + */ + explicit PrimitiveScalar(std::optional<T> value) : value_(std::move(value)) {} + + bool IsNull() const override { return !value_.has_value(); } + + /** + * @brief Gets the actual value held by the scalar. + * @return Reference to the value. + * @note Behavior is undefined if the scalar is null. + */ + const T& value() const { return *value_; } + + /** + * @brief (Deprecated) Type-specific accessor for raw value. + * @tparam U Must match T. + * @return Reference to the value if types match. + * @throws std::bad_cast if U does not match T. + */ + template <typename U> + const U& as() const { + if constexpr (std::is_same_v<T, U>) return *value_; + throw std::bad_cast(); + } + + std::shared_ptr<Scalar> clone() const override { + return std::make_shared<PrimitiveScalar<T>>(value_); + } + + void accept(ScalarVisitor& visitor) const override { + if (IsNull()) { + visitor.visitNull(); + } else { + visitor.visit(*value_); + } + } + + private: + std::optional<T> value_; +}; + +// Aliases for common primitive scalar types +using Int32Scalar = PrimitiveScalar<int32_t>; +using Int64Scalar = PrimitiveScalar<int64_t>; +using DoubleScalar = PrimitiveScalar<double>; +using StringScalar = PrimitiveScalar<std::string>; +using BoolScalar = PrimitiveScalar<bool>; + +/** + * @brief Base class for scalars that contain a vector of child Scalars. + * @tparam Derived The concrete subclass type (CRTP). + */ +template <typename Derived> +class VectorScalarBase : public Scalar { Review Comment: But this sounds like an anti-pattern in the OOP. You cannot use the base `VectorScalarBase` class without knowing its subclass implementation. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For additional commands, e-mail: issues-h...@iceberg.apache.org
