FileLock


1   /*
2    * Copyright (C) 2005 Alfresco, Inc.
3    *
4    * Licensed under the Mozilla Public License version 1.1 
5    * with a permitted attribution clause. You may obtain a
6    * copy of the License at
7    *
8    *   http://www.alfresco.org/legal/license.txt
9    *
10   * Unless required by applicable law or agreed to in writing,
11   * software distributed under the License is distributed on an
12   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
13   * either express or implied. See the License for the specific
14   * language governing permissions and limitations under the
15   * License.
16   */
17  package org.alfresco.filesys.locking;
18  
19  /**
20   * File Lock Class
21   * <p>
22   * Contains the details of a single file lock.
23   */
24  public class FileLock
25  {
26  
27      // Constants
28  
29      public static final long LockWholeFile = 0xFFFFFFFFFFFFFFFFL;
30  
31      // Start lock offset and length
32  
33      private long m_offset;
34      private long m_length;
35  
36      // Owner process id
37  
38      private int m_pid;
39  
40      /**
41       * Class constructor
42       * 
43       * @param offset long
44       * @param len long
45       * @param pid int
46       */
47      public FileLock(long offset, long len, int pid)
48      {
49          setOffset(offset);
50          setLength(len);
51          setProcessId(pid);
52      }
53  
54      /**
55       * Get the starting lock offset
56       * 
57       * @return long Starting lock offset.
58       */
59      public final long getOffset()
60      {
61          return m_offset;
62      }
63  
64      /**
65       * Set the starting lock offset.
66       * 
67       * @param long Starting lock offset
68       */
69      public final void setOffset(long offset)
70      {
71          m_offset = offset;
72      }
73  
74      /**
75       * Get the locked section length
76       * 
77       * @return long Locked section length
78       */
79      public final long getLength()
80      {
81          return m_length;
82      }
83  
84      /**
85       * Set the locked section length
86       * 
87       * @param long Locked section length
88       */
89      public final void setLength(long len)
90      {
91          if (len < 0)
92              m_length = LockWholeFile;
93          else
94              m_length = len;
95      }
96  
97      /**
98       * Get the owner process id for the lock
99       * 
100      * @return int
101      */
102     public final int getProcessId()
103     {
104         return m_pid;
105     }
106 
107     /**
108      * Deterine if the lock is locking the whole file
109      * 
110      * @return boolean
111      */
112     public final boolean isWholeFile()
113     {
114         return m_length == LockWholeFile ? true : false;
115     }
116 
117     /**
118      * Set the process id of the owner of this lock
119      * 
120      * @param pid int
121      */
122     public final void setProcessId(int pid)
123     {
124         m_pid = pid;
125     }
126 
127     /**
128      * Check if the specified locks byte range overlaps this locks byte range.
129      * 
130      * @param lock FileLock
131      */
132     public final boolean hasOverlap(FileLock lock)
133     {
134         return hasOverlap(lock.getOffset(), lock.getLength());
135     }
136 
137     /**
138      * Check if the specified locks byte range overlaps this locks byte range.
139      * 
140      * @param offset long
141      * @param len long
142      */
143     public final boolean hasOverlap(long offset, long len)
144     {
145 
146         // Check if the lock is for the whole file
147 
148         if (isWholeFile())
149             return true;
150 
151         // Check if the locks overlap
152 
153         long endOff = getOffset() + getLength();
154 
155         if (getOffset() < offset && endOff < offset)
156             return false;
157 
158         endOff = offset + len;
159 
160         if (getOffset() > endOff)
161             return false;
162 
163         // Locks overlap
164 
165         return true;
166     }
167 
168     /**
169      * Return the lock details as a string
170      * 
171      * @return String
172      */
173     public String   toString()
174     {
175         StringBuffer   str = new StringBuffer  ();
176 
177         str.append("[PID=");
178         str.append(getProcessId());
179         str.append(",Offset=");
180         str.append(getOffset());
181         str.append(",Len=");
182         str.append(getLength());
183         str.append("]");
184 
185         return str.toString();
186     }
187 }
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