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| 1 | +/* | |
| 2 | + * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved. | |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 | + * | |
| 5 | + * This code is free software; you can redistribute it and/or modify it | |
| 6 | + * under the terms of the GNU General Public License version 2 only, as | |
| 7 | + * published by the Free Software Foundation. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle in the LICENSE file that accompanied this code. | |
| 10 | + * | |
| 11 | + * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 12 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 | + * version 2 for more details (a copy is included in the LICENSE file that | |
| 15 | + * accompanied this code). | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License version | |
| 18 | + * 2 along with this work; if not, write to the Free Software Foundation, | |
| 19 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 20 | + * | |
| 21 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * questions. | |
| 24 | + */ | |
| 25 | + | |
| 26 | +package java.nio.file; | |
| 27 | + | |
| 28 | +import java.nio.file.attribute.*; | |
| 29 | +import java.io.IOException; | |
| 30 | +import java.util.*; | |
| 31 | +import sun.nio.fs.BasicFileAttributesHolder; | |
| 32 | + | |
| 33 | +/** | |
| 34 | + * Simple file tree walker that works in a similar manner to nftw(3C). | |
| 35 | + * | |
| 36 | + * @see Files#walkFileTree | |
| 37 | + */ | |
| 38 | + | |
| 39 | +class FileTreeWalker { | |
| 40 | + private final boolean followLinks; | |
| 41 | + private final LinkOption[] linkOptions; | |
| 42 | + private final FileVisitor<? super Path> visitor; | |
| 43 | + private final int maxDepth; | |
| 44 | + | |
| 45 | + FileTreeWalker(Set<FileVisitOption> options, | |
| 46 | + FileVisitor<? super Path> visitor, | |
| 47 | + int maxDepth) | |
| 48 | + { | |
| 49 | + boolean fl = false; | |
| 50 | + for (FileVisitOption option: options) { | |
| 51 | + // will throw NPE if options contains null | |
| 52 | + switch (option) { | |
| 53 | + case FOLLOW_LINKS : fl = true; break; | |
| 54 | + default: | |
| 55 | + throw new AssertionError("Should not get here"); | |
| 56 | + } | |
| 57 | + } | |
| 58 | + this.followLinks = fl; | |
| 59 | + this.linkOptions = (fl) ? new LinkOption[0] : | |
| 60 | + new LinkOption[] { LinkOption.NOFOLLOW_LINKS }; | |
| 61 | + this.visitor = visitor; | |
| 62 | + this.maxDepth = maxDepth; | |
| 63 | + } | |
| 64 | + | |
| 65 | + /** | |
| 66 | + * Walk file tree starting at the given file | |
| 67 | + */ | |
| 68 | + void walk(Path start) throws IOException { | |
| 69 | + FileVisitResult result = walk(start, | |
| 70 | + 0, | |
| 71 | + new ArrayList<AncestorDirectory>()); | |
| 72 | + Objects.requireNonNull(result, "FileVisitor returned null"); | |
| 73 | + } | |
| 74 | + | |
| 75 | + /** | |
| 76 | + * @param file | |
| 77 | + * the directory to visit | |
| 78 | + * @param depth | |
| 79 | + * depth remaining | |
| 80 | + * @param ancestors | |
| 81 | + * use when cycle detection is enabled | |
| 82 | + */ | |
| 83 | + private FileVisitResult walk(Path file, | |
| 84 | + int depth, | |
| 85 | + List<AncestorDirectory> ancestors) | |
| 86 | + throws IOException | |
| 87 | + { | |
| 88 | + // if attributes are cached then use them if possible | |
| 89 | + BasicFileAttributes attrs = null; | |
| 90 | + if ((depth > 0) && | |
| 91 | + (file instanceof BasicFileAttributesHolder) && | |
| 92 | + (System.getSecurityManager() == null)) | |
| 93 | + { | |
| 94 | + BasicFileAttributes cached = ((BasicFileAttributesHolder)file).get(); | |
| 95 | + if (!followLinks || !cached.isSymbolicLink()) | |
| 96 | + attrs = cached; | |
| 97 | + } | |
| 98 | + IOException exc = null; | |
| 99 | + | |
| 100 | + // attempt to get attributes of file. If fails and we are following | |
| 101 | + // links then a link target might not exist so get attributes of link | |
| 102 | + if (attrs == null) { | |
| 103 | + try { | |
| 104 | + try { | |
| 105 | + attrs = Files.readAttributes(file, BasicFileAttributes.class, linkOptions); | |
| 106 | + } catch (IOException x1) { | |
| 107 | + if (followLinks) { | |
| 108 | + try { | |
| 109 | + attrs = Files.readAttributes(file, | |
| 110 | + BasicFileAttributes.class, | |
| 111 | + LinkOption.NOFOLLOW_LINKS); | |
| 112 | + } catch (IOException x2) { | |
| 113 | + exc = x2; | |
| 114 | + } | |
| 115 | + } else { | |
| 116 | + exc = x1; | |
| 117 | + } | |
| 118 | + } | |
| 119 | + } catch (SecurityException x) { | |
| 120 | + // If access to starting file is denied then SecurityException | |
| 121 | + // is thrown, otherwise the file is ignored. | |
| 122 | + if (depth == 0) | |
| 123 | + throw x; | |
| 124 | + return FileVisitResult.CONTINUE; | |
| 125 | + } | |
| 126 | + } | |
| 127 | + | |
| 128 | + // unable to get attributes of file | |
| 129 | + if (exc != null) { | |
| 130 | + return visitor.visitFileFailed(file, exc); | |
| 131 | + } | |
| 132 | + | |
| 133 | + // at maximum depth or file is not a directory | |
| 134 | + if (depth >= maxDepth || !attrs.isDirectory()) { | |
| 135 | + return visitor.visitFile(file, attrs); | |
| 136 | + } | |
| 137 | + | |
| 138 | + // check for cycles when following links | |
| 139 | + if (followLinks) { | |
| 140 | + Object key = attrs.fileKey(); | |
| 141 | + | |
| 142 | + // if this directory and ancestor has a file key then we compare | |
| 143 | + // them; otherwise we use less efficient isSameFile test. | |
| 144 | + for (AncestorDirectory ancestor: ancestors) { | |
| 145 | + Object ancestorKey = ancestor.fileKey(); | |
| 146 | + if (key != null && ancestorKey != null) { | |
| 147 | + if (key.equals(ancestorKey)) { | |
| 148 | + // cycle detected | |
| 149 | + return visitor.visitFileFailed(file, | |
| 150 | + new FileSystemLoopException(file.toString())); | |
| 151 | + } | |
| 152 | + } else { | |
| 153 | + boolean isSameFile = false; | |
| 154 | + try { | |
| 155 | + isSameFile = Files.isSameFile(file, ancestor.file()); | |
| 156 | + } catch (IOException x) { | |
| 157 | + // ignore | |
| 158 | + } catch (SecurityException x) { | |
| 159 | + // ignore | |
| 160 | + } | |
| 161 | + if (isSameFile) { | |
| 162 | + // cycle detected | |
| 163 | + return visitor.visitFileFailed(file, | |
| 164 | + new FileSystemLoopException(file.toString())); | |
| 165 | + } | |
| 166 | + } | |
| 167 | + } | |
| 168 | + | |
| 169 | + ancestors.add(new AncestorDirectory(file, key)); | |
| 170 | + } | |
| 171 | + | |
| 172 | + // visit directory | |
| 173 | + try { | |
| 174 | + DirectoryStream<Path> stream = null; | |
| 175 | + FileVisitResult result; | |
| 176 | + | |
| 177 | + // open the directory | |
| 178 | + try { | |
| 179 | + stream = Files.newDirectoryStream(file); | |
| 180 | + } catch (IOException x) { | |
| 181 | + return visitor.visitFileFailed(file, x); | |
| 182 | + } catch (SecurityException x) { | |
| 183 | + // ignore, as per spec | |
| 184 | + return FileVisitResult.CONTINUE; | |
| 185 | + } | |
| 186 | + | |
| 187 | + // the exception notified to the postVisitDirectory method | |
| 188 | + IOException ioe = null; | |
| 189 | + | |
| 190 | + // invoke preVisitDirectory and then visit each entry | |
| 191 | + try { | |
| 192 | + result = visitor.preVisitDirectory(file, attrs); | |
| 193 | + if (result != FileVisitResult.CONTINUE) { | |
| 194 | + return result; | |
| 195 | + } | |
| 196 | + | |
| 197 | + try { | |
| 198 | + for (Path entry: stream) { | |
| 199 | + result = walk(entry, depth+1, ancestors); | |
| 200 | + | |
| 201 | + // returning null will cause NPE to be thrown | |
| 202 | + if (result == null || result == FileVisitResult.TERMINATE) | |
| 203 | + return result; | |
| 204 | + | |
| 205 | + // skip remaining siblings in this directory | |
| 206 | + if (result == FileVisitResult.SKIP_SIBLINGS) | |
| 207 | + break; | |
| 208 | + } | |
| 209 | + } catch (DirectoryIteratorException e) { | |
| 210 | + // IOException will be notified to postVisitDirectory | |
| 211 | + ioe = e.getCause(); | |
| 212 | + } | |
| 213 | + } finally { | |
| 214 | + try { | |
| 215 | + stream.close(); | |
| 216 | + } catch (IOException e) { | |
| 217 | + // IOException will be notified to postVisitDirectory | |
| 218 | + if (ioe == null) | |
| 219 | + ioe = e; | |
| 220 | + } | |
| 221 | + } | |
| 222 | + | |
| 223 | + // invoke postVisitDirectory last | |
| 224 | + return visitor.postVisitDirectory(file, ioe); | |
| 225 | + | |
| 226 | + } finally { | |
| 227 | + // remove key from trail if doing cycle detection | |
| 228 | + if (followLinks) { | |
| 229 | + ancestors.remove(ancestors.size()-1); | |
| 230 | + } | |
| 231 | + } | |
| 232 | + } | |
| 233 | + | |
| 234 | + private static class AncestorDirectory { | |
| 235 | + private final Path dir; | |
| 236 | + private final Object key; | |
| 237 | + AncestorDirectory(Path dir, Object key) { | |
| 238 | + this.dir = dir; | |
| 239 | + this.key = key; | |
| 240 | + } | |
| 241 | + Path file() { | |
| 242 | + return dir; | |
| 243 | + } | |
| 244 | + Object fileKey() { | |
| 245 | + return key; | |
| 246 | + } | |
| 247 | + } | |
| 248 | +} | |