ceph/src/arrow/cpp/src/arrow/json/parser.h

   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/json/options.h"
  24 #include "arrow/status.h"
  25 #include "arrow/util/key_value_metadata.h"
  26 #include "arrow/util/macros.h"
  27 #include "arrow/util/visibility.h"
  28
  29 namespace arrow {
  30
  31 class Array;
  32 class Buffer;
  33 class MemoryPool;
  34 class KeyValueMetadata;
  35 class ResizableBuffer;
  36
  37 namespace json {
  38
  39 struct Kind {
  40   enum type : uint8_t { kNull, kBoolean, kNumber, kString, kArray, kObject };
  41
  42   static const std::string& Name(Kind::type);
  43
  44   static const std::shared_ptr<const KeyValueMetadata>& Tag(Kind::type);
  45
  46   static Kind::type FromTag(const std::shared_ptr<const KeyValueMetadata>& tag);
  47
  48   static Status ForType(const DataType& type, Kind::type* kind);
  49 };
  50
  51 constexpr int32_t kMaxParserNumRows = 100000;
  52
  53 /// \class BlockParser
  54 /// \brief A reusable block-based parser for JSON data
  55 ///
  56 /// The parser takes a block of newline delimited JSON data and extracts Arrays
  57 /// of unconverted strings which can be fed to a Converter to obtain a usable Array.
  58 ///
  59 /// Note that in addition to parse errors (such as malformed JSON) some conversion
  60 /// errors are caught at parse time:
  61 /// - A null value in non-nullable column
  62 /// - Change in the JSON kind of a column. For example, if an explicit schema is provided
  63 ///   which stipulates that field "a" is integral, a row of {"a": "not a number"} will
  64 ///   result in an error. This also applies to fields outside an explicit schema.
  65 class ARROW_EXPORT BlockParser {
  66  public:
  67   virtual ~BlockParser() = default;
  68
  69   /// \brief Reserve storage for scalars parsed from a block of json
  70   virtual Status ReserveScalarStorage(int64_t nbytes) = 0;
  71
  72   /// \brief Parse a block of data
  73   virtual Status Parse(const std::shared_ptr<Buffer>& json) = 0;
  74
  75   /// \brief Extract parsed data
  76   virtual Status Finish(std::shared_ptr<Array>* parsed) = 0;
  77
  78   /// \brief Return the number of parsed rows
  79   int32_t num_rows() const { return num_rows_; }
  80
  81   /// \brief Construct a BlockParser
  82   ///
  83   /// \param[in] pool MemoryPool to use when constructing parsed array
  84   /// \param[in] options ParseOptions to use when parsing JSON
  85   /// \param[out] out constructed BlockParser
  86   static Status Make(MemoryPool* pool, const ParseOptions& options,
  87                      std::unique_ptr<BlockParser>* out);
  88
  89   static Status Make(const ParseOptions& options, std::unique_ptr<BlockParser>* out);
  90
  91  protected:
  92   ARROW_DISALLOW_COPY_AND_ASSIGN(BlockParser);
  93
  94   explicit BlockParser(MemoryPool* pool) : pool_(pool) {}
  95
  96   MemoryPool* pool_;
  97   int32_t num_rows_ = 0;
  98 };
  99
 100 }  // namespace json
 101 }  // namespace arrow