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+/*
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+ * Licensed to the Apache Software Foundation (ASF) under one
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+ * or more contributor license agreements. See the NOTICE file
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+ * distributed with this work for additional information
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+ * regarding copyright ownership. The ASF licenses this file
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+ * to you under the Apache License, Version 2.0 (the
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+ * "License"); you may not use this file except in compliance
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+ * with the License. You may obtain a copy of the License at
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+ *
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+ * http://www.apache.org/licenses/LICENSE-2.0
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+ *
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+ * Unless required by applicable law or agreed to in writing, software
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+ * distributed under the License is distributed on an "AS IS" BASIS,
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+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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+ * See the License for the specific language governing permissions and
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+ * limitations under the License.
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+ */
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+package org.apache.hadoop.hdfs.server.namenode.visitor;
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+
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+import org.apache.hadoop.hdfs.server.namenode.INode;
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+import org.apache.hadoop.hdfs.server.namenode.INodeDirectory;
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+import org.apache.hadoop.hdfs.server.namenode.INodeFile;
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+import org.apache.hadoop.hdfs.server.namenode.INodeReference;
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+import org.apache.hadoop.hdfs.server.namenode.INodeSymlink;
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+import org.apache.hadoop.hdfs.server.namenode.snapshot.DirectorySnapshottableFeature;
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+import org.apache.hadoop.hdfs.server.namenode.snapshot.DirectoryWithSnapshotFeature;
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+import org.apache.hadoop.hdfs.server.namenode.snapshot.Snapshot;
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+
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+import java.util.Iterator;
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+
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+/**
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+ * For visiting namespace trees.
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+ */
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+public interface NamespaceVisitor {
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+ /** For visiting any {@link INode}. */
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+ interface INodeVisitor {
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+ INodeVisitor DEFAULT = new INodeVisitor() {};
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+
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+ /** Visiting the given {@link INode}. */
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+ default void visit(INode iNode, int snapshot) {
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+ }
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+ }
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+
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+ /** @return the default (non-recursive) {@link INodeVisitor}. */
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+ default INodeVisitor getDefaultVisitor() {
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+ return INodeVisitor.DEFAULT;
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+ }
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+
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+ /** Visiting the given {@link INodeFile}. */
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+ default void visitFile(INodeFile file, int snapshot) {
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+ getDefaultVisitor().visit(file, snapshot);
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+ }
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+
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+ /** Visiting the given {@link INodeSymlink}. */
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+ default void visitSymlink(INodeSymlink symlink, int snapshot) {
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+ getDefaultVisitor().visit(symlink, snapshot);
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+ }
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+
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+ /** Visiting the given {@link INodeReference} (non-recursively). */
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+ default void visitReference(INodeReference ref, int snapshot) {
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+ getDefaultVisitor().visit(ref, snapshot);
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+ }
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+
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+ /** First visit the given {@link INodeReference} and then the referred. */
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+ default void visitReferenceRecursively(INodeReference ref, int snapshot) {
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+ visitReference(ref, snapshot);
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+
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+ final INode referred = ref.getReferredINode();
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+ preVisitReferred(referred);
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+ referred.accept(this, snapshot);
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+ postVisitReferred(referred);
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+ }
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+
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+ /** Right before visiting the given referred {@link INode}. */
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+ default void preVisitReferred(INode referred) {
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+ }
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+
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+ /** Right after visiting the given referred {@link INode}. */
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+ default void postVisitReferred(INode referred) {
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+ }
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+
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+ /** Visiting the given {@link INodeDirectory} (non-recursively). */
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+ default void visitDirectory(INodeDirectory dir, int snapshot) {
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+ getDefaultVisitor().visit(dir, snapshot);
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+ }
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+
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+ /**
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+ * First visit the given {@link INodeDirectory};
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+ * then the children;
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+ * and then, if snapshottable, the snapshots. */
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+ default void visitDirectoryRecursively(INodeDirectory dir, int snapshot) {
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+ visitDirectory(dir, snapshot);
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+ visitSubs(getChildren(dir, snapshot));
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+
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+ if (snapshot == Snapshot.CURRENT_STATE_ID) {
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+ final DirectorySnapshottableFeature snapshottable
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+ = dir.getDirectorySnapshottableFeature();
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+ if (snapshottable != null) {
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+ visitSnapshottable(dir, snapshottable);
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+ visitSubs(getSnapshots(snapshottable));
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+ }
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+ }
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+ }
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+
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+ /**
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+ * Right before visiting the given sub {@link Element}.
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+ * The sub element may be a child of an {@link INodeDirectory}
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+ * or a snapshot in {@link DirectorySnapshottableFeature}.
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+ *
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+ * @param sub the element to be visited.
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+ * @param index the index of the sub element.
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+ * @param isLast is the sub element the last element?
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+ */
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+ default void preVisitSub(Element sub, int index, boolean isLast) {
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+ }
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+
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+ /**
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+ * Right after visiting the given sub {@link Element}.
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+ * The sub element may be a child of an {@link INodeDirectory}
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+ * or a snapshot in {@link DirectorySnapshottableFeature}.
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+ *
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+ * @param sub the element just visited.
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+ * @param index the index of the sub element.
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+ * @param isLast is the sub element the last element?
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+ */
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+ default void postVisitSub(Element sub, int index, boolean isLast) {
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+ }
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+
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+ /** Visiting a {@link DirectorySnapshottableFeature}. */
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+ default void visitSnapshottable(INodeDirectory dir,
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+ DirectorySnapshottableFeature snapshottable) {
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+ }
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+
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+ /**
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+ * Visiting the sub {@link Element}s recursively.
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+ *
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+ * @param subs the children of an {@link INodeDirectory}
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+ * or the snapshots in {@link DirectorySnapshottableFeature}.
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+ */
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+ default void visitSubs(Iterable<Element> subs) {
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+ if (subs == null) {
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+ return;
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+ }
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+ int index = 0;
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+ for(final Iterator<Element> i = subs.iterator(); i.hasNext();) {
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+ final Element e = i.next();
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+ final boolean isList = !i.hasNext();
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+ preVisitSub(e, index, isList);
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+ e.getInode().accept(this, e.getSnapshotId());
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+ postVisitSub(e, index, isList);
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+ index++;
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+ }
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+ }
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+
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+ /** @return the children as {@link Element}s. */
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+ static Iterable<Element> getChildren(INodeDirectory dir, int snapshot) {
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+ final Iterator<INode> i = dir.getChildrenList(snapshot).iterator();
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+ return new Iterable<Element>() {
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+ @Override
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+ public Iterator<Element> iterator() {
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+ return new Iterator<Element>() {
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+ @Override
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+ public boolean hasNext() {
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+ return i.hasNext();
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+ }
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+
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+ @Override
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+ public Element next() {
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+ return new Element(snapshot, i.next());
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+ }
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+
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+ @Override
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+ public void remove() {
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+ throw new UnsupportedOperationException();
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+ }
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+ };
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+ }
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+ };
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+ }
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+
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+ /** @return the snapshots as {@link Element}s. */
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+ static Iterable<Element> getSnapshots(
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+ DirectorySnapshottableFeature snapshottable) {
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+ final Iterator<DirectoryWithSnapshotFeature.DirectoryDiff> i
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+ = snapshottable.getDiffs().iterator();
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+ return new Iterable<Element>() {
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+ @Override
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+ public Iterator<Element> iterator() {
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+ return new Iterator<Element>() {
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+ private DirectoryWithSnapshotFeature.DirectoryDiff next = findNext();
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+
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+ private DirectoryWithSnapshotFeature.DirectoryDiff findNext() {
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+ for(; i.hasNext();) {
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+ final DirectoryWithSnapshotFeature.DirectoryDiff diff = i.next();
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+ if (diff.isSnapshotRoot()) {
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+ return diff;
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+ }
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+ }
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+ return null;
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+ }
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+
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+ @Override
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+ public boolean hasNext() {
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+ return next != null;
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+ }
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+
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+ @Override
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+ public Element next() {
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+ final int id = next.getSnapshotId();
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+ final Element e = new Element(id,
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+ snapshottable.getSnapshotById(id).getRoot());
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+ next = findNext();
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+ return e;
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+ }
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+
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+ @Override
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+ public void remove() {
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+ throw new UnsupportedOperationException();
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+ }
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+ };
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+ }
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+ };
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+ }
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+
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+ /** Snapshot and INode. */
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+ class Element {
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+ private final int snapshotId;
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+ private final INode inode;
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+
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+ Element(int snapshot, INode inode) {
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+ this.snapshotId = snapshot;
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+ this.inode = inode;
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+ }
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+
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+ INode getInode() {
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+ return inode;
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+ }
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+
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+ int getSnapshotId() {
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+ return snapshotId;
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+ }
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+ }
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+}
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Tsz-Wo Nicholas Sze