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CursorIterator.scala
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CursorIterator.scala
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/*
* Copyright (c) 2002-2018 "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 <http://www.gnu.org/licenses/>.
*/
package org.neo4j.cypher.internal.spi
import org.neo4j.collection.PrimitiveLongResourceIterator
import org.neo4j.internal.kernel.api.helpers.RelationshipSelectionCursor
import org.neo4j.kernel.impl.api.store.RelationshipIterator
import org.neo4j.storageengine.api.RelationshipVisitor
import scala.collection.Iterator
abstract class CursorIterator[T] extends Iterator[T] {
private var _next: T = _
private var intialzed = false
protected def fetchNext(): T
protected def close(): Unit
override def hasNext: Boolean = {
if (!intialzed) {
_next = fetchNext()
intialzed = true
}
_next != null
}
override def next(): T = {
if (!hasNext) {
close()
Iterator.empty.next()
}
val current = _next
_next = fetchNext()
if (!hasNext) {
close()
}
current
}
}
class RelationshipCursorIterator(selectionCursor: RelationshipSelectionCursor) extends RelationshipIterator {
import RelationshipCursorIterator.{NOT_INITIALIZED, NO_ID}
private var _next = NOT_INITIALIZED
private var typeId: Int = NO_ID
private var source: Long = NO_ID
private var target: Long = NO_ID
override def relationshipVisit[EXCEPTION <: Exception](relationshipId: Long,
visitor: RelationshipVisitor[EXCEPTION]): Boolean = {
visitor.visit(relationshipId, typeId, source, target)
true
}
private def fetchNext(): Long = if (selectionCursor.next()) selectionCursor.relationshipReference() else -1L
override def hasNext: Boolean = {
if (_next == NOT_INITIALIZED) {
_next = fetchNext()
}
_next >= 0
}
//We store the current state in case the underlying cursor is
//closed when calling next.
private def storeState(): Unit = {
typeId = selectionCursor.`type`()
source = selectionCursor.sourceNodeReference()
target = selectionCursor.targetNodeReference()
}
override def next(): Long = {
if (!hasNext) {
selectionCursor.close()
Iterator.empty.next()
}
val current = _next
storeState()
//Note that if no more elements are found the selection cursor
//will be closed so no need to do a extra check after fetching.
_next = fetchNext()
current
}
}
object RelationshipCursorIterator {
private val NOT_INITIALIZED = -2L
private val NO_ID = -1
}
abstract class PrimitiveCursorIterator extends PrimitiveLongResourceIterator {
private var _next: Long = fetchNext()
protected def fetchNext(): Long
override def hasNext: Boolean = _next >= 0
override def next(): Long = {
if (!hasNext) {
close()
Iterator.empty.next()
}
val current = _next
_next = fetchNext()
if (!hasNext) close()
current
}
}