1 /*
2 * Copyright (c) 2007, 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. 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
31 /**
32 * Storage for files. A {@code FileStore} represents a storage pool, device,
33 * partition, volume, concrete file system or other implementation specific means
34 * of file storage. The {@code FileStore} for where a file is stored is obtained
35 * by invoking the {@link Files#getFileStore getFileStore} method, or all file
36 * stores can be enumerated by invoking the {@link FileSystem#getFileStores
37 * getFileStores} method.
38 *
39 * <p> In addition to the methods defined by this class, a file store may support
40 * one or more {@link FileStoreAttributeView FileStoreAttributeView} classes
41 * that provide a read-only or updatable view of a set of file store attributes.
42 *
43 * @since 1.7
44 */
45
46 public abstract class FileStore {
47
48 /**
49 * Initializes a new instance of this class.
50 */
51 protected FileStore() {
52 }
53
54 /**
55 * Returns the name of this file store. The format of the name is highly
56 * implementation specific. It will typically be the name of the storage
57 * pool or volume.
58 *
59 * <p> The string returned by this method may differ from the string
60 * returned by the {@link Object#toString() toString} method.
61 *
62 * @return the name of this file store
63 */
64 public abstract String name();
65
66 /**
67 * Returns the <em>type</em> of this file store. The format of the string
68 * returned by this method is highly implementation specific. It may
69 * indicate, for example, the format used or if the file store is local
70 * or remote.
71 *
72 * @return a string representing the type of this file store
73 */
74 public abstract String type();
75
76 /**
77 * Tells whether this file store is read-only. A file store is read-only if
78 * it does not support write operations or other changes to files. Any
79 * attempt to create a file, open an existing file for writing etc. causes
80 * an {@code IOException} to be thrown.
81 *
82 * @return {@code true} if, and only if, this file store is read-only
83 */
84 public abstract boolean isReadOnly();
85
86 /**
87 * Returns the size, in bytes, of the file store.
88 *
89 * @return the size of the file store, in bytes
90 *
91 * @throws IOException
92 * if an I/O error occurs
93 */
94 public abstract long getTotalSpace() throws IOException;
95
96 /**
97 * Returns the number of bytes available to this Java virtual machine on the
98 * file store.
99 *
100 * <p> The returned number of available bytes is a hint, but not a
101 * guarantee, that it is possible to use most or any of these bytes. The
102 * number of usable bytes is most likely to be accurate immediately
103 * after the space attributes are obtained. It is likely to be made inaccurate
104 * by any external I/O operations including those made on the system outside
105 * of this Java virtual machine.
106 *
107 * @return the number of bytes available
108 *
109 * @throws IOException
110 * if an I/O error occurs
111 */
112 public abstract long getUsableSpace() throws IOException;
113
114 /**
115 * Returns the number of unallocated bytes in the file store.
116 *
117 * <p> The returned number of unallocated bytes is a hint, but not a
118 * guarantee, that it is possible to use most or any of these bytes. The
119 * number of unallocated bytes is most likely to be accurate immediately
120 * after the space attributes are obtained. It is likely to be
121 * made inaccurate by any external I/O operations including those made on
122 * the system outside of this virtual machine.
123 *
124 * @return the number of unallocated bytes
125 *
126 * @throws IOException
127 * if an I/O error occurs
128 */
129 public abstract long getUnallocatedSpace() throws IOException;
130
131 /**
132 * Tells whether or not this file store supports the file attributes
133 * identified by the given file attribute view.
134 *
135 * <p> Invoking this method to test if the file store supports {@link
136 * BasicFileAttributeView} will always return {@code true}. In the case of
137 * the default provider, this method cannot guarantee to give the correct
138 * result when the file store is not a local storage device. The reasons for
139 * this are implementation specific and therefore unspecified.
140 *
141 * @param type
142 * the file attribute view type
143 *
144 * @return {@code true} if, and only if, the file attribute view is
145 * supported
146 */
147 public abstract boolean supportsFileAttributeView(Class<? extends FileAttributeView> type);
148
149 /**
150 * Tells whether or not this file store supports the file attributes
151 * identified by the given file attribute view.
152 *
153 * <p> Invoking this method to test if the file store supports {@link
154 * BasicFileAttributeView}, identified by the name "{@code basic}" will
155 * always return {@code true}. In the case of the default provider, this
156 * method cannot guarantee to give the correct result when the file store is
157 * not a local storage device. The reasons for this are implementation
158 * specific and therefore unspecified.
159 *
160 * @param name
161 * the {@link FileAttributeView#name name} of file attribute view
162 *
163 * @return {@code true} if, and only if, the file attribute view is
164 * supported
165 */
166 public abstract boolean supportsFileAttributeView(String name);
167
168 /**
169 * Returns a {@code FileStoreAttributeView} of the given type.
170 *
171 * <p> This method is intended to be used where the file store attribute
172 * view defines type-safe methods to read or update the file store attributes.
173 * The {@code type} parameter is the type of the attribute view required and
174 * the method returns an instance of that type if supported.
175 *
176 * @param <V>
177 * The {@code FileStoreAttributeView} type
178 * @param type
179 * the {@code Class} object corresponding to the attribute view
180 *
181 * @return a file store attribute view of the specified type or
182 * {@code null} if the attribute view is not available
183 */
184 public abstract <V extends FileStoreAttributeView> V
185 getFileStoreAttributeView(Class<V> type);
186
187 /**
188 * Reads the value of a file store attribute.
189 *
190 * <p> The {@code attribute} parameter identifies the attribute to be read
191 * and takes the form:
192 * <blockquote>
193 * <i>view-name</i><b>:</b><i>attribute-name</i>
194 * </blockquote>
195 * where the character {@code ':'} stands for itself.
196 *
197 * <p> <i>view-name</i> is the {@link FileStoreAttributeView#name name} of
198 * a {@link FileStore AttributeView} that identifies a set of file attributes.
199 * <i>attribute-name</i> is the name of the attribute.
200 *
201 * <p> <b>Usage Example:</b>
202 * Suppose we want to know if ZFS compression is enabled (assuming the "zfs"
203 * view is supported):
204 * <pre>
205 * boolean compression = (Boolean)fs.getAttribute("zfs:compression");
206 * </pre>
207 *
208 * @param attribute
209 * the attribute to read
210
211 * @return the attribute value; {@code null} may be valid for some
212 * attributes
213 *
214 * @throws UnsupportedOperationException
215 * if the attribute view is not available or it does not support
216 * reading the attribute
217 * @throws IOException
218 * if an I/O error occurs
219 */
220 public abstract Object getAttribute(String attribute) throws IOException;
221 }