Table.h

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/*
 * (C) Copyright 1996-2018 ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 * In applying this licence, ECMWF does not waive the privileges and immunities
 * granted to it by virtue of its status as an intergovernmental organisation nor
 * does it submit to any jurisdiction.
 */
 
/// @author Simon Smart
/// @date Dec 2018
 
#ifndef odc_core_Table_H
#define odc_core_Table_H
 
#include <memory>
 
#include "eckit/io/Buffer.h"
 
#include "odc/core/ThreadSharedDataHandle.h"
#include "odc/core/MetaData.h"
#include "odc/core/Span.h"
 
 
namespace eckit { class DataHandle; }
 
namespace odc {
namespace core {
 
class DecodeTarget;
 
//----------------------------------------------------------------------------------------------------------------------
 
 
class Table {
 
public: // methods
 
    // Construct a table. This is a static function rather than a constructor
    // so that we can return false for no-more-data rather than throwing an
    // exception
 
    static std::unique_ptr<Table> readTable(ThreadSharedDataHandle& dh);
 
    eckit::Offset startPosition() const;
    eckit::Offset nextPosition() const;
    eckit::Length encodedDataSize() const;
 
    size_t rowCount() const;
    size_t columnCount() const;
    int32_t byteOrder() const;
    bool otherByteOrder() const;
 
    const MetaData& columns() const;
    const Properties& properties() const;
 
    eckit::Buffer readEncodedData();
 
    void decode(DecodeTarget& target);
 
    Span span(const std::vector<std::string>& columns, bool onlyConstant=false);
    Span decodeSpan(const std::vector<std::string>& columns);
 
private: // methods
 
    Table(const ThreadSharedDataHandle& dh);
 
    /// Lookups used for decoding. Memoised for efficiency
    const std::map<std::string, size_t>& columnLookup();
    const std::map<std::string, size_t>& simpleColumnLookup();
 
private: // members
 
    ThreadSharedDataHandle dh_;
 
    eckit::Offset startPosition_;
    eckit::Offset dataPosition_;
    eckit::Length dataSize_;
    eckit::Offset nextPosition_;
    int32_t byteOrder_;
 
    MetaData metadata_;
    Properties properties_;
 
    // Lookups. Memoised for efficiency
 
    std::map<std::string, size_t> columnLookup_;
    std::map<std::string, size_t> simpleColumnLookup_;
};
 
 
//----------------------------------------------------------------------------------------------------------------------
 
} // namespace core
} // namespace odc
 
#endif