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/**
* Copyright (C) 2021-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/bson/bsonelement.h"
#include "mongo/bson/bsonmisc.h"
#include "mongo/bson/util/builder.h"
#include "mongo/bson/util/simple8b.h"
#include "mongo/platform/int128.h"
#include <memory>
namespace mongo {
/**
* Class to build BSON Subtype 7 (Column) binaries.
*/
class BSONColumnBuilder {
public:
BSONColumnBuilder(StringData fieldName);
/**
* Appends a BSONElement to this BSONColumnBuilder.
*
* Value will be stored delta compressed if possible and uncompressed otherwise.
*
* The field name will be ignored.
*/
BSONColumnBuilder& append(BSONElement elem);
/**
* Appends an index skip to this BSONColumnBuilder.
*/
BSONColumnBuilder& skip();
/**
* Returns the field name this BSONColumnBuilder was created with.
*/
StringData fieldName() const {
return _fieldName;
}
/**
* Finalizes the BSON Column and returns the BinData binary.
*
* The BSONColumnBuilder must remain in scope for the pointer to be valid.
*/
BSONBinData finalize();
private:
BSONElement _previous() const;
void _storePrevious(BSONElement elem);
void _writeLiteralFromPrevious();
void _incrementSimple8bCount();
bool _usesDeltaOfDelta(BSONType type);
bool _objectIdDeltaPossible(BSONElement elem, BSONElement prev);
// Helper to append doubles to this Column builder. Returns true if append was successful and
// false if the value needs to be stored uncompressed.
bool _appendDouble(double value, double previous);
// Tries to rescale current pending values + one additional value into a new Simple8bBuilder.
// Returns the new Simple8bBuilder if rescaling was possible and none otherwise.
boost::optional<Simple8bBuilder<uint64_t>> _tryRescalePending(int64_t encoded,
uint8_t newScaleIndex);
Simple8bWriteFn _createBufferWriter();
// Storage for the previously appended BSONElement
std::unique_ptr<char[]> _prev;
int _prevSize = 0;
int _prevCapacity = 0;
// This is only used for types that use delta of delta.
int64_t _prevDelta = 0;
// Simple-8b builder for storing compressed deltas
Simple8bBuilder<uint64_t> _simple8bBuilder64;
Simple8bBuilder<uint128_t> _simple8bBuilder128;
// Offset to last Simple-8b control byte
std::ptrdiff_t _controlByteOffset = 0;
// Additional variables needed for previous state
int64_t _prevEncoded64 = 0;
int128_t _prevEncoded128 = 0;
double _lastValueInPrevBlock = 0;
uint8_t _scaleIndex;
// Buffer for the BSON Column binary
BufBuilder _bufBuilder;
// Field name
std::string _fieldName;
// Chose whether to use 128 or 64 Simple-8b builder
bool _storeWith128 = false;
};
} // namespace mongo
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