CreateFileTree.java revision 9330:8b1f1c2a400f 
1/*
2 * Copyright (c) 2008, 2013, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24import java.nio.file.*;
25import java.io.IOException;
26import java.util.*;
27
28/**
29 * Creates a file tree with possible cycles caused by symbolic links
30 * to ancestor directories.
31 */
32
33public class CreateFileTree {
34
35    private static final Random rand = new Random();
36
37    private static boolean supportsLinks(Path dir) {
38        Path link = dir.resolve("testlink");
39        Path target = dir.resolve("testtarget");
40        try {
41            Files.createSymbolicLink(link, target);
42            Files.delete(link);
43            return true;
44        } catch (UnsupportedOperationException x) {
45            return false;
46        } catch (IOException x) {
47            return false;
48        }
49    }
50
51    static Path create() throws IOException {
52        Path top = Files.createTempDirectory("tree");
53        List<Path> dirs = new ArrayList<Path>();
54
55        // create tree
56        Queue<Path> queue = new ArrayDeque<Path>();
57        queue.add(top);
58        int total = 1 + rand.nextInt(20);
59        int n = 0;
60        Path dir;
61        while (((dir = queue.poll()) != null) && (n < total)) {
62            int r = Math.min((total-n), (1+rand.nextInt(3)));
63            for (int i=0; i<r; i++) {
64                String name = "dir" + (++n);
65                Path subdir = Files.createDirectory(dir.resolve(name));
66                queue.offer(subdir);
67                dirs.add(subdir);
68            }
69        }
70
71        // create a few regular files in the file tree
72        int files = dirs.size() * 3;
73        for (int i=0; i<files; i++) {
74            String name = "file" + (i+1);
75            int x = rand.nextInt(dirs.size());
76            Files.createFile(dirs.get(x).resolve(name));
77        }
78
79        // create a few sym links in the file tree so as to create cycles
80        if (supportsLinks(top)) {
81            int links = 1 + rand.nextInt(5);
82            for (int i=0; i<links; i++) {
83                int x = rand.nextInt(dirs.size());
84                int y;
85                do {
86                    y = rand.nextInt(dirs.size());
87                } while (y != x);
88                String name = "link" + (i+1);
89                Path link = dirs.get(x).resolve(name);
90                Path target = dirs.get(y);
91                Files.createSymbolicLink(link, target);
92            }
93        }
94
95         return top;
96    }
97
98    public static void main(String[] args) throws IOException {
99        Path top = create();
100        System.out.println(top);
101    }
102}
103