include/arrow/visit_type_inline.h

0001 // Licensed to the Apache Software Foundation (ASF) under one
0002 // or more contributor license agreements.  See the NOTICE file
0003 // distributed with this work for additional information
0004 // regarding copyright ownership.  The ASF licenses this file
0005 // to you under the Apache License, Version 2.0 (the
0006 // "License"); you may not use this file except in compliance
0007 // with the License.  You may obtain a copy of the License at
0008 //
0009 //   http://www.apache.org/licenses/LICENSE-2.0
0010 //
0011 // Unless required by applicable law or agreed to in writing,
0012 // software distributed under the License is distributed on an
0013 // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
0014 // KIND, either express or implied.  See the License for the
0015 // specific language governing permissions and limitations
0016 // under the License.
0017
0018 #pragma once
0019
0020 #include "arrow/extension_type.h"
0021 #include "arrow/type.h"
0022 #include "arrow/util/macros.h"
0023 #include "arrow/visitor_generate.h"
0024
0025 namespace arrow {
0026
0027 #define TYPE_VISIT_INLINE(TYPE_CLASS)                                            \
0028   case TYPE_CLASS##Type::type_id:                                                \
0029     return visitor->Visit(internal::checked_cast<const TYPE_CLASS##Type&>(type), \
0030                           std::forward<ARGS>(args)...);
0031
0032 /// \brief Calls `visitor` with the corresponding concrete type class
0033 ///
0034 /// \tparam VISITOR Visitor type that implements Visit() for all Arrow types.
0035 /// \tparam ARGS Additional arguments, if any, will be passed to the Visit function after
0036 /// the `type` argument
0037 /// \return Status
0038 ///
0039 /// A visitor is a type that implements specialized logic for each Arrow type.
0040 /// Example usage:
0041 ///
0042 /// ```
0043 /// class ExampleVisitor {
0044 ///   arrow::Status Visit(const arrow::Int32Type& type) { ... }
0045 ///   arrow::Status Visit(const arrow::Int64Type& type) { ... }
0046 ///   ...
0047 /// }
0048 /// ExampleVisitor visitor;
0049 /// VisitTypeInline(some_type, &visitor);
0050 /// ```
0051 template <typename VISITOR, typename... ARGS>
0052 inline Status VisitTypeInline(const DataType& type, VISITOR* visitor, ARGS&&... args) {
0053   switch (type.id()) {
0054     ARROW_GENERATE_FOR_ALL_TYPES(TYPE_VISIT_INLINE);
0055     default:
0056       break;
0057   }
0058   return Status::NotImplemented("Type not implemented");
0059 }
0060
0061 #undef TYPE_VISIT_INLINE
0062
0063 #define TYPE_VISIT_INLINE(TYPE_CLASS)                          \
0064   case TYPE_CLASS##Type::type_id:                              \
0065     return std::forward<VISITOR>(visitor)(                     \
0066         internal::checked_cast<const TYPE_CLASS##Type&>(type), \
0067         std::forward<ARGS>(args)...);
0068
0069 /// \brief Call `visitor` with the corresponding concrete type class
0070 /// \tparam ARGS Additional arguments, if any, will be passed to the Visit function after
0071 /// the `type` argument
0072 ///
0073 /// Unlike VisitTypeInline which calls `visitor.Visit`, here `visitor`
0074 /// itself is called.
0075 /// `visitor` must support a `const DataType&` argument as a fallback,
0076 /// in addition to concrete type classes.
0077 ///
0078 /// The intent is for this to be called on a generic lambda
0079 /// that may internally use `if constexpr` or similar constructs.
0080 template <typename VISITOR, typename... ARGS>
0081 inline auto VisitType(const DataType& type, VISITOR&& visitor, ARGS&&... args)
0082     -> decltype(std::forward<VISITOR>(visitor)(type, args...)) {
0083   switch (type.id()) {
0084     ARROW_GENERATE_FOR_ALL_TYPES(TYPE_VISIT_INLINE);
0085     default:
0086       break;
0087   }
0088   return std::forward<VISITOR>(visitor)(type, std::forward<ARGS>(args)...);
0089 }
0090
0091 #undef TYPE_VISIT_INLINE
0092
0093 #define TYPE_ID_VISIT_INLINE(TYPE_CLASS)                              \
0094   case TYPE_CLASS##Type::type_id: {                                   \
0095     const TYPE_CLASS##Type* concrete_ptr = NULLPTR;                   \
0096     return visitor->Visit(concrete_ptr, std::forward<ARGS>(args)...); \
0097   }
0098
0099 /// \brief Calls `visitor` with a nullptr of the corresponding concrete type class
0100 ///
0101 /// \tparam VISITOR Visitor type that implements Visit() for all Arrow types.
0102 /// \tparam ARGS Additional arguments, if any, will be passed to the Visit function after
0103 /// the `type` argument
0104 /// \return Status
0105 template <typename VISITOR, typename... ARGS>
0106 inline Status VisitTypeIdInline(Type::type id, VISITOR* visitor, ARGS&&... args) {
0107   switch (id) {
0108     ARROW_GENERATE_FOR_ALL_TYPES(TYPE_ID_VISIT_INLINE);
0109     default:
0110       break;
0111   }
0112   return Status::NotImplemented("Type not implemented");
0113 }
0114
0115 #undef TYPE_ID_VISIT_INLINE
0116
0117 }  // namespace arrow