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1 | // Licensed to the Apache Software Foundation (ASF) under one |
2 | // or more contributor license agreements. See the NOTICE file | |
3 | // distributed with this work for additional information | |
4 | // regarding copyright ownership. The ASF licenses this file | |
5 | // to you under the Apache License, Version 2.0 (the | |
6 | // "License"); you may not use this file except in compliance | |
7 | // with the License. You may obtain a copy of the License at | |
8 | // | |
9 | // http://www.apache.org/licenses/LICENSE-2.0 | |
10 | // | |
11 | // Unless required by applicable law or agreed to in writing, | |
12 | // software distributed under the License is distributed on an | |
13 | // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | |
14 | // KIND, either express or implied. See the License for the | |
15 | // specific language governing permissions and limitations | |
16 | // under the License. | |
17 | ||
18 | #pragma once | |
19 | ||
20 | #include <memory> | |
21 | #include <string> | |
22 | ||
23 | #include "arrow/status.h" | |
24 | #include "arrow/util/macros.h" | |
25 | #include "arrow/util/visibility.h" | |
26 | ||
27 | namespace arrow { | |
28 | ||
29 | class Array; | |
30 | class DataType; | |
31 | class Field; | |
32 | class MemoryPool; | |
33 | ||
34 | namespace json { | |
35 | ||
36 | /// \brief interface for conversion of Arrays | |
37 | /// | |
38 | /// Converters are not required to be correct for arbitrary input- only | |
39 | /// for unconverted arrays emitted by a corresponding parser. | |
40 | class ARROW_EXPORT Converter { | |
41 | public: | |
42 | virtual ~Converter() = default; | |
43 | ||
44 | /// convert an array | |
45 | /// on failure, this converter may be promoted to another converter which | |
46 | /// *can* convert the given input. | |
47 | virtual Status Convert(const std::shared_ptr<Array>& in, | |
48 | std::shared_ptr<Array>* out) = 0; | |
49 | ||
50 | std::shared_ptr<DataType> out_type() const { return out_type_; } | |
51 | ||
52 | MemoryPool* pool() { return pool_; } | |
53 | ||
54 | protected: | |
55 | ARROW_DISALLOW_COPY_AND_ASSIGN(Converter); | |
56 | ||
57 | Converter(MemoryPool* pool, const std::shared_ptr<DataType>& out_type) | |
58 | : pool_(pool), out_type_(out_type) {} | |
59 | ||
60 | MemoryPool* pool_; | |
61 | std::shared_ptr<DataType> out_type_; | |
62 | }; | |
63 | ||
64 | /// \brief produce a single converter to the specified out_type | |
65 | ARROW_EXPORT Status MakeConverter(const std::shared_ptr<DataType>& out_type, | |
66 | MemoryPool* pool, std::shared_ptr<Converter>* out); | |
67 | ||
68 | class ARROW_EXPORT PromotionGraph { | |
69 | public: | |
70 | virtual ~PromotionGraph() = default; | |
71 | ||
72 | /// \brief produce a valid field which will be inferred as null | |
73 | virtual std::shared_ptr<Field> Null(const std::string& name) const = 0; | |
74 | ||
75 | /// \brief given an unexpected field encountered during parsing, return a type to which | |
76 | /// it may be convertible (may return null if none is available) | |
77 | virtual std::shared_ptr<DataType> Infer( | |
78 | const std::shared_ptr<Field>& unexpected_field) const = 0; | |
79 | ||
80 | /// \brief given a type to which conversion failed, return a promoted type to which | |
81 | /// conversion may succeed (may return null if none is available) | |
82 | virtual std::shared_ptr<DataType> Promote( | |
83 | const std::shared_ptr<DataType>& failed, | |
84 | const std::shared_ptr<Field>& unexpected_field) const = 0; | |
85 | ||
86 | protected: | |
87 | ARROW_DISALLOW_COPY_AND_ASSIGN(PromotionGraph); | |
88 | PromotionGraph() = default; | |
89 | }; | |
90 | ||
91 | ARROW_EXPORT const PromotionGraph* GetPromotionGraph(); | |
92 | ||
93 | } // namespace json | |
94 | } // namespace arrow |