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StringSchemaKey.java
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StringSchemaKey.java
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/*
* Copyright (c) 2002-2018 "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 <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.impl.index.schema;
import java.util.Arrays;
import org.neo4j.index.internal.gbptree.GBPTree;
import org.neo4j.string.UTF8;
import org.neo4j.values.storable.Value;
import org.neo4j.values.storable.Values;
import static java.lang.String.format;
/**
* Includes value and entity id (to be able to handle non-unique values). A value can be any {@link String},
* or rather any string that {@link GBPTree} can handle.
*/
class StringSchemaKey extends NativeSchemaKey<StringSchemaKey>
{
static final int ENTITY_ID_SIZE = Long.BYTES;
private boolean ignoreLength;
// UTF-8 bytes, grows on demand. Actual length is dictated by bytesLength field.
byte[] bytes;
int bytesLength;
// Set to true when the internal byte[] have been handed out to an UTF8Value, so that the next call to setBytesLength
// will be forced to allocate a new array. The byte[] isn't cleared with null since this key still logically contains those bytes.
private boolean bytesDereferenced;
int size()
{
return ENTITY_ID_SIZE + bytesLength;
}
@Override
protected Value assertCorrectType( Value value )
{
if ( !Values.isTextValue( value ) )
{
throw new IllegalArgumentException(
"Key layout does only support strings, tried to create key from " + value );
}
return value;
}
@Override
void initialize( long entityId )
{
super.initialize( entityId );
ignoreLength = false;
}
@Override
public Value asValue()
{
if ( bytes == null )
{
return Values.NO_VALUE;
}
// Dereference our bytes so that we won't overwrite it on next read
bytesDereferenced = true;
return Values.utf8Value( bytes, 0, bytesLength );
}
@Override
void initValueAsLowest()
{
bytes = null;
}
@Override
void initValueAsHighest()
{
bytes = null;
}
void initAsPrefixLow( String prefix )
{
writeString( prefix );
initialize( Long.MIN_VALUE );
// Don't set ignoreLength = true here since the "low" a.k.a. left side of the range should care about length.
// This will make the prefix lower than those that matches the prefix (their length is >= that of the prefix)
}
void initAsPrefixHigh( String prefix )
{
writeString( prefix );
initialize( Long.MAX_VALUE );
ignoreLength = true;
}
private boolean isHighest()
{
return getCompareId() && getEntityId() == Long.MAX_VALUE && bytes == null;
}
/**
* Compares the value of this key to that of another key.
* This method is expected to be called in scenarios where inconsistent reads may happen (and later retried).
*
* @param other the {@link StringSchemaKey} to compare to.
* @return comparison against the {@code other} {@link StringSchemaKey}.
*/
@Override
int compareValueTo( StringSchemaKey other )
{
if ( bytes != other.bytes )
{
if ( bytes == null )
{
return isHighest() ? 1 : -1;
}
if ( other.bytes == null )
{
return other.isHighest() ? -1 : 1;
}
}
else
{
return 0;
}
return unsignedByteArrayCompare( bytes, bytesLength, other.bytes, other.bytesLength, ignoreLength | other.ignoreLength );
}
private static int unsignedByteArrayCompare( byte[] a, int aLength, byte[] b, int bLength, boolean ignoreLength )
{
assert a != null && b != null : "Null arrays not supported.";
if ( a == b && aLength == bLength )
{
return 0;
}
int length = Math.min( aLength, bLength );
for ( int i = 0; i < length; i++ )
{
int compare = Short.compare( (short) (a[i] & 0xFF), (short) (b[i] & 0xFF) );
if ( compare != 0 )
{
return compare;
}
}
return ignoreLength ? 0 : Integer.compare( aLength, bLength );
}
@Override
public String toString()
{
return format( "value=%s,entityId=%d,bytes=%s",
asValue(),
getEntityId(),
bytes == null ? "null" : Arrays.toString( Arrays.copyOf( bytes, bytesLength ) ) );
}
@Override
public void writeString( String value )
{
bytes = UTF8.encode( value );
bytesLength = bytes.length;
bytesDereferenced = false;
}
@Override
public void writeString( char value )
{
writeString( String.valueOf( value ) );
}
void copyFrom( StringSchemaKey key )
{
setBytesLength( key.bytesLength );
System.arraycopy( key.bytes, 0, bytes, 0, key.bytesLength );
setEntityId( key.getEntityId() );
setCompareId( key.getCompareId() );
}
/**
* Ensures that the internal byte[] is long enough, or longer than the given {@code length}.
* Also sets the internal {@code bytesLength} field to the given {@code length} so that interactions with the byte[]
* from this point on will use that for length, instead of the length of the byte[].
*
* @param length minimum length that the internal byte[] needs to be.
*/
void setBytesLength( int length )
{
if ( bytesDereferenced || bytes == null || bytes.length < length )
{
bytesDereferenced = false;
// allocate a bit more than required so that there's a higher chance that this byte[] instance
// can be used for more keys than just this one
bytes = new byte[length + length / 2];
}
bytesLength = length;
}
}