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Neo4j property value system.
There is a newer version: 5.26.0
/*
 * Copyright (c) 2002-2020 "Neo4j,"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.values;

import org.neo4j.values.storable.FloatingPointValue;
import org.neo4j.values.storable.NumberValue;

public abstract class AnyValue
{
    private int hash;

    // this should be final, but Mockito barfs if it is,
    // so we need to just manually ensure it isn't overridden
    @Override
    public boolean equals( Object other )
    {
        return this == other || other != null && equalTo( other );
    }

    @Override
    public final int hashCode()
    {
        //We will always recompute hashcode for values
        //where `hashCode == 0`, e.g. empty strings and empty lists
        //however that shouldn't be shouldn't be too costly
        if ( hash == 0 )
        {
            hash = computeHash();
        }
        return hash;
    }

    protected abstract boolean equalTo( Object other );

    protected abstract int computeHash();

    public abstract  void writeTo( AnyValueWriter writer ) throws E;

    public boolean isSequenceValue()
    {
        return false; // per default Values are no SequenceValues
    }

    public abstract Equality ternaryEquals( AnyValue other );

    public abstract  T map( ValueMapper mapper );

    public abstract String getTypeName();

    /**
     * Estimation of the bytes used for whatever payload the AnyValue is wrapping.
     *
     *For example a LongValue wraps a long that consumes 4 bytes.
     * @return The number of bytes the internal value consumes.
     */
    protected abstract long estimatedPayloadSize();

    /**
     * Gives an estimation of the heap usage in bytes for the given value.
     * 
     * The estimation assumes a 64bit JVM with 32 bit references (-XX:+UseCompressedOops) but is fairly accurate
     * for simple values even without these assumptions. However for complicated types such as lists and maps these
     * values are very crude estimates, typically something like size * NUMBER since we don't want to pay the
     * price of (potentially recursively) iterate over the individual elements.
     *
     * @return an estimation of how many bytes this value consumes.
     */
    public long estimatedHeapUsage()
    {
        //Each AnyValue has a 12 bit header and stores a 4 byte int for the hash
        return pad( 16 + estimatedPayloadSize() );
    }

    /**
     * pads the value to nearest next multiple of 8
     * @param value the value to pad
     * @return the value padded to the nearest multiple of 8
     */
    public static long pad( long value )
    {
        return ((value + 7) / 8) * 8;
    }

    /**
     * @return {@code true} if at least one operand is NaN and the other is a number
     */
    public static boolean isNanAndNumber( AnyValue value1, AnyValue value2 )
    {
        return (value1 instanceof FloatingPointValue && ((FloatingPointValue) value1).isNaN() && value2 instanceof NumberValue)
               || (value2 instanceof FloatingPointValue && ((FloatingPointValue) value2).isNaN() && value1 instanceof NumberValue);
    }

    /**
     * @return {@code true} if at least one operand is NaN
     */
    public static boolean hasNaNOperand( AnyValue value1, AnyValue value2 )
    {
        return (value1 instanceof FloatingPointValue && ((FloatingPointValue) value1).isNaN())
               || (value2 instanceof FloatingPointValue && ((FloatingPointValue) value2).isNaN());
    }
}