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// 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.
/// User-defined extension types. EXPERIMENTAL in 0.13.0
/// \since 0.13.0
#pragma once
#include <memory>
#include <string>
#include "arrow/array.h"
#include "arrow/type.h"
#include "arrow/util/visibility.h"
namespace arrow {
/// \brief The base class for custom / user-defined types.
class ARROW_EXPORT ExtensionType : public DataType {
public:
static constexpr Type::type type_id = Type::EXTENSION;
/// \brief The type of array used to represent this extension type's data
std::shared_ptr<DataType> storage_type() const { return storage_type_; }
DataTypeLayout layout() const override;
std::string ToString() const override;
std::string name() const override;
/// \brief Unique name of extension type used to identify type for
/// serialization
/// \return the string name of the extension
virtual std::string extension_name() const = 0;
/// \brief Determine if two instances of the same extension types are
/// equal. Invoked from ExtensionType::Equals
/// \param[in] other the type to compare this type with
/// \return bool true if type instances are equal
virtual bool ExtensionEquals(const ExtensionType& other) const = 0;
/// \brief Wrap built-in Array type in a user-defined ExtensionArray instance
/// \param[in] data the physical storage for the extension type
virtual std::shared_ptr<Array> MakeArray(std::shared_ptr<ArrayData> data) const = 0;
/// \brief Create an instance of the ExtensionType given the actual storage
/// type and the serialized representation
/// \param[in] storage_type the physical storage type of the extension
/// \param[in] serialized_data the serialized representation produced by
/// Serialize
/// \param[out] out the reconstructed extension type
/// \return Status
virtual Status Deserialize(std::shared_ptr<DataType> storage_type,
const std::string& serialized_data,
std::shared_ptr<DataType>* out) const = 0;
/// \brief Create a serialized representation of the extension type's
/// metadata. The storage type will be handled automatically in IPC code
/// paths
/// \return the serialized representation
virtual std::string Serialize() const = 0;
protected:
explicit ExtensionType(std::shared_ptr<DataType> storage_type)
: DataType(Type::EXTENSION), storage_type_(storage_type) {}
std::shared_ptr<DataType> storage_type_;
};
/// \brief Base array class for user-defined extension types
class ARROW_EXPORT ExtensionArray : public Array {
public:
/// \brief Construct an ExtensionArray from an ArrayData.
///
/// The ArrayData must have the right ExtensionType.
explicit ExtensionArray(const std::shared_ptr<ArrayData>& data);
/// \brief Construct an ExtensionArray from a type and the underlying storage.
ExtensionArray(const std::shared_ptr<DataType>& type,
const std::shared_ptr<Array>& storage);
const ExtensionType* extension_type() const {
return internal::checked_cast<const ExtensionType*>(data_->type.get());
}
/// \brief The physical storage for the extension array
std::shared_ptr<Array> storage() const { return storage_; }
protected:
void SetData(const std::shared_ptr<ArrayData>& data);
std::shared_ptr<Array> storage_;
};
/// \brief Register an extension type globally. The name returned by the type's
/// extension_name() method should be unique. This method is thread-safe
/// \param[in] type an instance of the extension type
/// \return Status
ARROW_EXPORT
Status RegisterExtensionType(std::shared_ptr<ExtensionType> type);
/// \brief Delete an extension type from the global registry. This method is
/// thread-safe
/// \param[in] type_name the unique name of a registered extension type
/// \return Status error if the type name is unknown
ARROW_EXPORT
Status UnregisterExtensionType(const std::string& type_name);
/// \brief Retrieve an extension type from the global registry. Returns nullptr
/// if not found. This method is thread-safe
/// \return the globally-registered extension type
ARROW_EXPORT
std::shared_ptr<ExtensionType> GetExtensionType(const std::string& type_name);
} // namespace arrow
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