/*
* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package java.nio.file;
import java.nio.file.attribute.*;
import java.io.IOException;
import java.util.*;
import sun.nio.fs.BasicFileAttributesHolder;
/**
* Simple file tree walker that works in a similar manner to nftw(3C).
*
* @see Files#walkFileTree
*/
class FileTreeWalker {
private final boolean followLinks;
private final LinkOption[] linkOptions;
private final FileVisitor<? super Path> visitor;
private final int maxDepth;
FileTreeWalker(Set<FileVisitOption> options,
FileVisitor<? super Path> visitor,
int maxDepth)
{
boolean fl = false;
for (FileVisitOption option: options) {
// will throw NPE if options contains null
switch (option) {
case FOLLOW_LINKS : fl = true; break;
default:
throw new AssertionError("Should not get here");
}
}
this.followLinks = fl;
this.linkOptions = (fl) ? new LinkOption[0] :
new LinkOption[] { LinkOption.NOFOLLOW_LINKS };
this.visitor = visitor;
this.maxDepth = maxDepth;
}
/**
* Walk file tree starting at the given file
*/
void walk(Path start) throws IOException {
FileVisitResult result = walk(start,
0,
new ArrayList<AncestorDirectory>());
Objects.requireNonNull(result, "FileVisitor returned null");
}
/**
* @param file
* the directory to visit
* @param depth
* depth remaining
* @param ancestors
* use when cycle detection is enabled
*/
private FileVisitResult walk(Path file,
int depth,
List<AncestorDirectory> ancestors)
throws IOException
{
// if attributes are cached then use them if possible
BasicFileAttributes attrs = null;
if ((depth > 0) &&
(file instanceof BasicFileAttributesHolder) &&
(System.getSecurityManager() == null))
{
BasicFileAttributes cached = ((BasicFileAttributesHolder)file).get();
if (!followLinks || !cached.isSymbolicLink())
attrs = cached;
}
IOException exc = null;
// attempt to get attributes of file. If fails and we are following
// links then a link target might not exist so get attributes of link
if (attrs == null) {
try {
try {
attrs = Files.readAttributes(file, BasicFileAttributes.class, linkOptions);
} catch (IOException x1) {
if (followLinks) {
try {
attrs = Files.readAttributes(file,
BasicFileAttributes.class,
LinkOption.NOFOLLOW_LINKS);
} catch (IOException x2) {
exc = x2;
}
} else {
exc = x1;
}
}
} catch (SecurityException x) {
// If access to starting file is denied then SecurityException
// is thrown, otherwise the file is ignored.
if (depth == 0)
throw x;
return FileVisitResult.CONTINUE;
}
}
// unable to get attributes of file
if (exc != null) {
return visitor.visitFileFailed(file, exc);
}
// at maximum depth or file is not a directory
if (depth >= maxDepth || !attrs.isDirectory()) {
return visitor.visitFile(file, attrs);
}
// check for cycles when following links
if (followLinks) {
Object key = attrs.fileKey();
// if this directory and ancestor has a file key then we compare
// them; otherwise we use less efficient isSameFile test.
for (AncestorDirectory ancestor: ancestors) {
Object ancestorKey = ancestor.fileKey();
if (key != null && ancestorKey != null) {
if (key.equals(ancestorKey)) {
// cycle detected
return visitor.visitFileFailed(file,
new FileSystemLoopException(file.toString()));
}
} else {
boolean isSameFile = false;
try {
isSameFile = Files.isSameFile(file, ancestor.file());
} catch (IOException x) {
// ignore
} catch (SecurityException x) {
// ignore
}
if (isSameFile) {
// cycle detected
return visitor.visitFileFailed(file,
new FileSystemLoopException(file.toString()));
}
}
}
ancestors.add(new AncestorDirectory(file, key));
}
// visit directory
try {
DirectoryStream<Path> stream = null;
FileVisitResult result;
// open the directory
try {
stream = Files.newDirectoryStream(file);
} catch (IOException x) {
return visitor.visitFileFailed(file, x);
} catch (SecurityException x) {
// ignore, as per spec
return FileVisitResult.CONTINUE;
}
// the exception notified to the postVisitDirectory method
IOException ioe = null;
// invoke preVisitDirectory and then visit each entry
try {
result = visitor.preVisitDirectory(file, attrs);
if (result != FileVisitResult.CONTINUE) {
return result;
}
try {
for (Path entry: stream) {
result = walk(entry, depth+1, ancestors);
// returning null will cause NPE to be thrown
if (result == null || result == FileVisitResult.TERMINATE)
return result;
// skip remaining siblings in this directory
if (result == FileVisitResult.SKIP_SIBLINGS)
break;
}
} catch (DirectoryIteratorException e) {
// IOException will be notified to postVisitDirectory
ioe = e.getCause();
}
} finally {
try {
stream.close();
} catch (IOException e) {
// IOException will be notified to postVisitDirectory
if (ioe == null)
ioe = e;
}
}
// invoke postVisitDirectory last
return visitor.postVisitDirectory(file, ioe);
} finally {
// remove key from trail if doing cycle detection
if (followLinks) {
ancestors.remove(ancestors.size()-1);
}
}
}
private static class AncestorDirectory {
private final Path dir;
private final Object key;
AncestorDirectory(Path dir, Object key) {
this.dir = dir;
this.key = key;
}
Path file() {
return dir;
}
Object fileKey() {
return key;
}
}
}