1 /*
2 * Copyright (C) 2005-2015 Schlichtherle IT Services.
3 * All rights reserved. Use is subject to license terms.
4 */
5 package net.java.truevfs.kernel.spec;
6
7 import java.io.IOException;
8 import javax.annotation.concurrent.Immutable;
9
10 /**
11 * Defines common access options for I/O operations.
12 * Not all options may be supported or available for all operations and
13 * certain combinations may even be illegal.
14 * It's up to the particular operation and file system driver implementation
15 * to define which options are supported and available.
16 * If an option is not supported, it should get silently ignored.
17 * If an option is not available or illegal, an {@link IOException} must get
18 * thrown.
19 *
20 * @author Christian Schlichtherle
21 */
22 @Immutable
23 public enum FsAccessOption {
24
25 /** Whether or not a file system node must be exclusively created. */
26 EXCLUSIVE,
27
28 /**
29 * Whether or not the contents of an existing file system node shall get
30 * kept for appending rather than replaced for overwriting.
31 */
32 APPEND,
33
34 /**
35 * Whether or not the entry data shall get cached for subsequent access.
36 * As a desired side effect, caching allows a federated file system (i.e.
37 * prospective archive file) to {@link FsController#sync} its contents to
38 * its parent file system while some client is still busy on reading
39 * or writing the cached entry data.
40 */
41 CACHE,
42
43 /**
44 * Whether or not any missing parent directory entries shall get created
45 * automatically with an undefined last modification time.
46 */
47 CREATE_PARENTS,
48
49 /**
50 * Expresses a preference to allow an archive file to grow by appending any
51 * new or updated archive entry contents or meta data to its end.
52 * Setting this option may produce redundant data in the resulting archive
53 * file.
54 * However, it may yield much better performance if the number and contents
55 * of the archive entries to create or update are rather small compared to
56 * the total size of the resulting archive file.
57 * <p>
58 * This option is the equivalent to a multi-session disc (CD, DVD etc.)
59 * for archive files.
60 * <p>
61 * Note that this option may get ignored by archive file system drivers.
62 * Furthermore, if this happens, there may be no direct feedback available
63 * to the caller.
64 */
65 GROW,
66
67 /**
68 * Expresses a preference to store an entry uncompressed within its archive.
69 * <p>
70 * Note that this option may get ignored by archive file system drivers.
71 * Furthermore, if this happens, there may be no direct feedback available
72 * to the caller.
73 */
74 STORE,
75
76 /**
77 * Expresses a preference to compress an entry within its archive.
78 * <p>
79 * Note that this option may get ignored by archive file system drivers.
80 * Furthermore, if this happens, there may be no direct feedback available
81 * to the caller.
82 */
83 COMPRESS,
84
85 /**
86 * Expresses a preference to encrypt archive entries when writing them to
87 * an archive file.
88 * <p>
89 * Note that this option may get ignored by archive file system drivers.
90 * Furthermore, if this happens, there may be no direct feedback available
91 * to the caller.
92 */
93 ENCRYPT,
94 }