001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.fs;
019
020import java.util.Arrays;
021
022import org.apache.commons.lang.builder.EqualsBuilder;
023import org.apache.commons.lang.builder.HashCodeBuilder;
024import org.apache.hadoop.classification.InterfaceAudience;
025
026/**
027 * XAttr is the POSIX Extended Attribute model similar to that found in
028 * traditional Operating Systems.  Extended Attributes consist of one
029 * or more name/value pairs associated with a file or directory. Five
030 * namespaces are defined: user, trusted, security, system and raw.
031 *   1) USER namespace attributes may be used by any user to store
032 *   arbitrary information. Access permissions in this namespace are
033 *   defined by a file directory's permission bits. For sticky directories,
034 *   only the owner and privileged user can write attributes.
035 * <br>
036 *   2) TRUSTED namespace attributes are only visible and accessible to
037 *   privileged users. This namespace is available from both user space
038 *   (filesystem API) and fs kernel.
039 * <br>
040 *   3) SYSTEM namespace attributes are used by the fs kernel to store
041 *   system objects.  This namespace is only available in the fs
042 *   kernel. It is not visible to users.
043 * <br>
044 *   4) SECURITY namespace attributes are used by the fs kernel for
045 *   security features. It is not visible to users.
046 * <br>
047 *   5) RAW namespace attributes are used for internal system attributes that
048 *   sometimes need to be exposed. Like SYSTEM namespace attributes they are
049 *   not visible to the user except when getXAttr/getXAttrs is called on a file
050 *   or directory in the /.reserved/raw HDFS directory hierarchy.  These
051 *   attributes can only be accessed by the superuser.
052 * <p/>
053 * @see <a href="http://en.wikipedia.org/wiki/Extended_file_attributes">
054 * http://en.wikipedia.org/wiki/Extended_file_attributes</a>
055 *
056 */
057@InterfaceAudience.Private
058public class XAttr {
059
060  public enum NameSpace {
061    USER,
062    TRUSTED,
063    SECURITY,
064    SYSTEM,
065    RAW
066  }
067
068  private final NameSpace ns;
069  private final String name;
070  private final byte[] value;
071
072  public static class Builder {
073    private NameSpace ns = NameSpace.USER;
074    private String name;
075    private byte[] value;
076
077    public Builder setNameSpace(NameSpace ns) {
078      this.ns = ns;
079      return this;
080    }
081
082    public Builder setName(String name) {
083      this.name = name;
084      return this;
085    }
086
087    public Builder setValue(byte[] value) {
088      this.value = value;
089      return this;
090    }
091
092    public XAttr build() {
093      return new XAttr(ns, name, value);
094    }
095  }
096
097  private XAttr(NameSpace ns, String name, byte[] value) {
098    this.ns = ns;
099    this.name = name;
100    this.value = value;
101  }
102
103  public NameSpace getNameSpace() {
104    return ns;
105  }
106
107  public String getName() {
108    return name;
109  }
110
111  public byte[] getValue() {
112    return value;
113  }
114
115  @Override
116  public int hashCode() {
117    return new HashCodeBuilder(811, 67)
118        .append(name)
119        .append(ns)
120        .append(value)
121        .toHashCode();
122  }
123
124  @Override
125  public boolean equals(Object obj) {
126    if (obj == null) { return false; }
127    if (obj == this) { return true; }
128    if (obj.getClass() != getClass()) {
129      return false;
130    }
131    XAttr rhs = (XAttr) obj;
132    return new EqualsBuilder()
133        .append(ns, rhs.ns)
134        .append(name, rhs.name)
135        .append(value, rhs.value)
136        .isEquals();
137  }
138
139  /**
140   * Similar to {@link #equals(Object)}, except ignores the XAttr value.
141   *
142   * @param obj to compare equality
143   * @return if the XAttrs are equal, ignoring the XAttr value
144   */
145  public boolean equalsIgnoreValue(Object obj) {
146    if (obj == null) { return false; }
147    if (obj == this) { return true; }
148    if (obj.getClass() != getClass()) {
149      return false;
150    }
151    XAttr rhs = (XAttr) obj;
152    return new EqualsBuilder()
153        .append(ns, rhs.ns)
154        .append(name, rhs.name)
155        .isEquals();
156  }
157
158  @Override
159  public String toString() {
160    return "XAttr [ns=" + ns + ", name=" + name + ", value="
161        + Arrays.toString(value) + "]";
162  }
163}