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102 lines
3.3 KiB
C++
102 lines
3.3 KiB
C++
// Licensed to the Apache Software Foundation (ASF) under one
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// or more contributor license agreements. See the NOTICE file
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// distributed with this work for additional information
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// regarding copyright ownership. The ASF licenses this file
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// to you under the Apache License, Version 2.0 (the
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// "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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#pragma once
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#include <memory>
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#include <string>
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#include "arrow/json/options.h"
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#include "arrow/status.h"
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#include "arrow/util/key_value_metadata.h"
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#include "arrow/util/macros.h"
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#include "arrow/util/visibility.h"
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namespace arrow {
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class Array;
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class Buffer;
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class MemoryPool;
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class KeyValueMetadata;
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class ResizableBuffer;
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namespace json {
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struct Kind {
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enum type : uint8_t { kNull, kBoolean, kNumber, kString, kArray, kObject };
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static const std::string& Name(Kind::type);
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static const std::shared_ptr<const KeyValueMetadata>& Tag(Kind::type);
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static Kind::type FromTag(const std::shared_ptr<const KeyValueMetadata>& tag);
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static Status ForType(const DataType& type, Kind::type* kind);
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};
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constexpr int32_t kMaxParserNumRows = 100000;
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/// \class BlockParser
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/// \brief A reusable block-based parser for JSON data
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///
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/// The parser takes a block of newline delimited JSON data and extracts Arrays
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/// of unconverted strings which can be fed to a Converter to obtain a usable Array.
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///
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/// Note that in addition to parse errors (such as malformed JSON) some conversion
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/// errors are caught at parse time:
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/// - A null value in non-nullable column
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/// - Change in the JSON kind of a column. For example, if an explicit schema is provided
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/// which stipulates that field "a" is integral, a row of {"a": "not a number"} will
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/// result in an error. This also applies to fields outside an explicit schema.
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class ARROW_EXPORT BlockParser {
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public:
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virtual ~BlockParser() = default;
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/// \brief Reserve storage for scalars parsed from a block of json
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virtual Status ReserveScalarStorage(int64_t nbytes) = 0;
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/// \brief Parse a block of data
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virtual Status Parse(const std::shared_ptr<Buffer>& json) = 0;
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/// \brief Extract parsed data
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virtual Status Finish(std::shared_ptr<Array>* parsed) = 0;
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/// \brief Return the number of parsed rows
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int32_t num_rows() const { return num_rows_; }
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/// \brief Construct a BlockParser
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///
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/// \param[in] pool MemoryPool to use when constructing parsed array
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/// \param[in] options ParseOptions to use when parsing JSON
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/// \param[out] out constructed BlockParser
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static Status Make(MemoryPool* pool, const ParseOptions& options,
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std::unique_ptr<BlockParser>* out);
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static Status Make(const ParseOptions& options, std::unique_ptr<BlockParser>* out);
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protected:
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ARROW_DISALLOW_COPY_AND_ASSIGN(BlockParser);
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explicit BlockParser(MemoryPool* pool) : pool_(pool) {}
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MemoryPool* pool_;
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int32_t num_rows_ = 0;
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};
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} // namespace json
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} // namespace arrow
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