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Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.
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/*
 * Copyright (c) 2002-2015 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.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.kernel.impl.store;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;

import org.neo4j.kernel.impl.store.record.DynamicRecord;
import org.neo4j.kernel.impl.store.record.NodeRecord;
import org.neo4j.kernel.impl.util.Bits;

import static java.lang.Long.highestOneBit;
import static java.lang.String.format;
import static org.neo4j.collection.primitive.PrimitiveLongCollections.EMPTY_LONG_ARRAY;
import static org.neo4j.kernel.impl.store.LabelIdArray.concatAndSort;
import static org.neo4j.kernel.impl.store.LabelIdArray.filter;
import static org.neo4j.kernel.impl.store.NodeLabelsField.parseLabelsBody;
import static org.neo4j.kernel.impl.util.Bits.bits;
import static org.neo4j.kernel.impl.util.Bits.bitsFromLongs;

public class InlineNodeLabels implements NodeLabels
{
    private static final int LABEL_BITS = 36;
    private final long labelField;
    private final NodeRecord node;

    public InlineNodeLabels( long labelField, NodeRecord node )
    {
        this.labelField = labelField;
        this.node = node;
    }

    @Override
    public long[] get( NodeStore nodeStore )
    {
        return get( node );
    }

    public static long[] get( NodeRecord node )
    {
        return parseInlined( node.getLabelField() );
    }

    @Override
    public long[] getIfLoaded()
    {
        return parseInlined( labelField );
    }

    @Override
    public Collection put( long[] labelIds, NodeStore nodeStore, DynamicRecordAllocator allocator )
    {
        Arrays.sort( labelIds );
        return putSorted( node, labelIds, nodeStore, allocator );
    }

    public static Collection putSorted( NodeRecord node, long[] labelIds,
            NodeStore nodeStore, DynamicRecordAllocator allocator )
    {
        if ( tryInlineInNodeRecord( node, labelIds, node.getDynamicLabelRecords() ) )
        {
            return Collections.emptyList();
        }

        return DynamicNodeLabels.putSorted( node, labelIds, nodeStore, allocator );
    }

    @Override
    public Collection add( long labelId, NodeStore nodeStore, DynamicRecordAllocator allocator )
    {
        long[] augmentedLabelIds = labelCount( labelField ) == 0 ? new long[]{labelId} :
                                   concatAndSort( parseInlined( labelField ), labelId );

        return putSorted( node, augmentedLabelIds, nodeStore, allocator );
    }

    @Override
    public Collection remove( long labelId, NodeStore nodeStore )
    {
        long[] newLabelIds = filter( parseInlined( labelField ), labelId );
        boolean inlined = tryInlineInNodeRecord( node, newLabelIds, node.getDynamicLabelRecords() );
        assert inlined;
        return Collections.emptyList();
    }

    static boolean tryInlineInNodeRecord( NodeRecord node, long[] ids, Collection changedDynamicRecords )
    {
        // We reserve the high header bit for future extensions of the format of the in-lined label bits
        // i.e. the 0-valued high header bit can allow for 0-7 in-lined labels in the bit-packed format.
        if ( ids.length > 7 )
        {
            return false;
        }

        byte bitsPerLabel = (byte) (ids.length > 0 ? (LABEL_BITS / ids.length) : LABEL_BITS);
        Bits bits = bits( 5 );
        if ( !inlineValues( ids, bitsPerLabel, bits ) )
        {
            return false;
        }
        node.setLabelField( combineLabelCountAndLabelStorage( (byte) ids.length, bits.getLongs()[0] ),
                            changedDynamicRecords );
        return true;
    }

    private static boolean inlineValues( long[] values, int maxBitsPerLabel, Bits target )
    {
        long limit = 1L << maxBitsPerLabel;
        for ( long value : values )
        {
            if ( highestOneBit( value ) < limit )
            {
                target.put( value, maxBitsPerLabel );
            }
            else
            {
                return false;
            }
        }
        return true;
    }

    public static long[] parseInlined( long labelField )
    {
        byte numberOfLabels = labelCount( labelField );
        if ( numberOfLabels == 0 )
        {
            return EMPTY_LONG_ARRAY;
        }

        long existingLabelsField = parseLabelsBody( labelField );
        byte bitsPerLabel = (byte) (LABEL_BITS / numberOfLabels);
        Bits bits = bitsFromLongs( new long[]{existingLabelsField} );
        long[] result = new long[numberOfLabels];
        for ( int i = 0; i < result.length; i++ )
        {
            result[i] = bits.getLong( bitsPerLabel );
        }
        return result;
    }

    private static long combineLabelCountAndLabelStorage( byte labelCount, long labelBits )
    {
        return ((((long)labelCount) << 36) | labelBits);
    }

    private static byte labelCount( long labelField )
    {
        return (byte) ((labelField & 0xF000000000L) >>> 36);
    }

    @Override
    public boolean isInlined()
    {
        return true;
    }

    @Override
    public String toString()
    {
        return format( "Inline(0x%x:%s)", node.getLabelField(), Arrays.toString( getIfLoaded(/*it is*/ ) ) );
    }
}