FileSystem


1   /*
2    * @(#)FileSystem.java  1.13 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package java.io;
9   
10  
11  /**
12   * Package-private abstract class for the local filesystem abstraction.
13   */
14  
15  abstract class FileSystem {
16  
17      /**
18       * Return the FileSystem object representing this platform's local
19       * filesystem.
20       */
21      public static native FileSystem   getFileSystem();
22  
23  
24      /* -- Normalization and construction -- */
25  
26      /**
27       * Return the local filesystem's name-separator character.
28       */
29      public abstract char getSeparator();
30  
31      /**
32       * Return the local filesystem's path-separator character.
33       */
34      public abstract char getPathSeparator();
35  
36      /**
37       * Convert the given pathname string to normal form.  If the string is
38       * already in normal form then it is simply returned.
39       */
40      public abstract String   normalize(String   path);
41  
42      /**
43       * Compute the length of this pathname string's prefix.  The pathname
44       * string must be in normal form.
45       */
46      public abstract int prefixLength(String   path);
47  
48      /**
49       * Resolve the child pathname string against the parent.
50       * Both strings must be in normal form, and the result
51       * will be in normal form.
52       */
53      public abstract String   resolve(String   parent, String   child);
54  
55      /**
56       * Return the parent pathname string to be used when the parent-directory
57       * argument in one of the two-argument File constructors is the empty
58       * pathname.
59       */
60      public abstract String   getDefaultParent();
61  
62      /**
63       * Post-process the given URI path string if necessary.  This is used on
64       * win32, e.g., to transform "/c:/foo" into "c:/foo".  The path string
65       * still has slash separators; code in the File class will translate them
66       * after this method returns.
67       */
68      public abstract String   fromURIPath(String   path);
69  
70  
71      /* -- Path operations -- */
72  
73      /**
74       * Tell whether or not the given abstract pathname is absolute.
75       */
76      public abstract boolean isAbsolute(File   f);
77  
78      /**
79       * Resolve the given abstract pathname into absolute form.  Invoked by the
80       * getAbsolutePath and getCanonicalPath methods in the File class.
81       */
82      public abstract String   resolve(File   f);
83  
84      public abstract String   canonicalize(String   path) throws IOException  ;
85  
86  
87      /* -- Attribute accessors -- */
88  
89      /* Constants for simple boolean attributes */
90      public static final int BA_EXISTS    = 0x01;
91      public static final int BA_REGULAR   = 0x02;
92      public static final int BA_DIRECTORY = 0x04;
93      public static final int BA_HIDDEN    = 0x08;
94  
95      /**
96       * Return the simple boolean attributes for the file or directory denoted
97       * by the given abstract pathname, or zero if it does not exist or some
98       * other I/O error occurs.
99       */
100     public abstract int getBooleanAttributes(File   f);
101 
102     /**
103      * Check whether the file or directory denoted by the given abstract
104      * pathname may be accessed by this process.  If the second argument is
105      * <code>false</code>, then a check for read access is made; if the second
106      * argument is <code>true</code>, then a check for write (not read-write)
107      * access is made.  Return false if access is denied or an I/O error
108      * occurs.
109      */
110     public abstract boolean checkAccess(File   f, boolean write);
111 
112     /**
113      * Return the time at which the file or directory denoted by the given
114      * abstract pathname was last modified, or zero if it does not exist or
115      * some other I/O error occurs.
116      */
117     public abstract long getLastModifiedTime(File   f);
118 
119     /**
120      * Return the length in bytes of the file denoted by the given abstract
121      * pathname, or zero if it does not exist, is a directory, or some other
122      * I/O error occurs.
123      */
124     public abstract long getLength(File   f);
125 
126 
127     /* -- File operations -- */
128 
129     /**
130      * Create a new empty file with the given pathname.  Return
131      * <code>true</code> if the file was created and <code>false</code> if a
132      * file or directory with the given pathname already exists.  Throw an
133      * IOException if an I/O error occurs.
134      */
135     public abstract boolean createFileExclusively(String   pathname)
136     throws IOException  ;
137 
138     /**
139      * Delete the file or directory denoted by the given abstract pathname,
140      * returning <code>true</code> if and only if the operation succeeds.
141      */
142     public abstract boolean delete(File   f);
143 
144     /**
145      * Arrange for the file or directory denoted by the given abstract
146      * pathname to be deleted when the VM exits, returning <code>true</code> if
147      * and only if the operation succeeds.
148      */
149     public abstract boolean deleteOnExit(File   f);
150 
151     /**
152      * List the elements of the directory denoted by the given abstract
153      * pathname.  Return an array of strings naming the elements of the
154      * directory if successful; otherwise, return <code>null</code>.
155      */
156     public abstract String  [] list(File   f);
157 
158     /**
159      * Create a new directory denoted by the given abstract pathname,
160      * returning <code>true</code> if and only if the operation succeeds.
161      */
162     public abstract boolean createDirectory(File   f);
163 
164     /**
165      * Rename the file or directory denoted by the first abstract pathname to
166      * the second abstract pathname, returning <code>true</code> if and only if
167      * the operation succeeds.
168      */
169     public abstract boolean rename(File   f1, File   f2);
170 
171     /**
172      * Set the last-modified time of the file or directory denoted by the
173      * given abstract pathname, returning <code>true</code> if and only if the
174      * operation succeeds.
175      */
176     public abstract boolean setLastModifiedTime(File   f, long time);
177 
178     /**
179      * Mark the file or directory denoted by the given abstract pathname as
180      * read-only, returning <code>true</code> if and only if the operation
181      * succeeds.
182      */
183     public abstract boolean setReadOnly(File   f);
184 
185 
186     /* -- Filesystem interface -- */
187 
188     /**
189      * List the available filesystem roots.
190      */
191     public abstract File  [] listRoots();
192 
193 
194     /* -- Basic infrastructure -- */
195 
196     /**
197      * Compare two abstract pathnames lexicographically.
198      */
199     public abstract int compare(File   f1, File   f2);
200 
201     /**
202      * Compute the hash code of an abstract pathname.
203      */
204     public abstract int hashCode(File   f);
205 
206     // Flags for enabling/disabling performance optimizations for file
207     // name canonicalization
208     static boolean useCanonCaches      = true;
209     static boolean useCanonPrefixCache = true;
210 
211     private static boolean getBooleanProperty(String   prop, boolean defaultVal) {
212         String   val = System.getProperty(prop);
213         if (val == null) return defaultVal;
214         if (val.equalsIgnoreCase("true")) {
215             return true;
216         } else {
217             return false;
218         }
219     }
220 
221     static {
222         useCanonCaches      = getBooleanProperty("sun.io.useCanonCaches",
223                                                  useCanonCaches);
224         useCanonPrefixCache = getBooleanProperty("sun.io.useCanonPrefixCache",
225                                                  useCanonPrefixCache);
226     }
227 }
228
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