SimpleFSLockFactory.cs

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/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;

namespace Lucene.Net.Store
{
    
    /// <summary> <p/>Implements <see cref="LockFactory" /> using <see cref="System.IO.FileInfo.Create()" />
    ///.<p/>
    /// 
    /// <p/><b>NOTE:</b> the <a target="_top"
    /// href="http://java.sun.com/j2se/1.4.2/docs/api/java/io/File.html#createNewFile()">javadocs
    /// for <c>File.createNewFile</c></a> contain a vague
    /// yet spooky warning about not using the API for file
    /// locking.  This warning was added due to <a target="_top"
    /// href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4676183">this
    /// bug</a>, and in fact the only known problem with using
    /// this API for locking is that the Lucene write lock may
    /// not be released when the JVM exits abnormally.<p/>
    /// <p/>When this happens, a <see cref="LockObtainFailedException" />
    /// is hit when trying to create a writer, in which case you
    /// need to explicitly clear the lock file first.  You can
    /// either manually remove the file, or use the 
    /// <see cref="Lucene.Net.Index.IndexWriter.Unlock(Directory)" />
    /// API.  But, first be certain that no writer is in fact
    /// writing to the index otherwise you can easily corrupt
    /// your index.<p/>
    /// 
    /// <p/>If you suspect that this or any other LockFactory is
    /// not working properly in your environment, you can easily
    /// test it by using <see cref="VerifyingLockFactory" />, <see cref="LockVerifyServer" />
    /// and <see cref="LockStressTest" />.<p/>
    /// 
    /// </summary>
    /// <seealso cref="LockFactory">
    /// </seealso>
    
    public class SimpleFSLockFactory:FSLockFactory
    {
        
        /// <summary> Create a SimpleFSLockFactory instance, with null (unset)
        /// lock directory. When you pass this factory to a <see cref="FSDirectory" />
        /// subclass, the lock directory is automatically set to the
        /// directory itsself. Be sure to create one instance for each directory
        /// your create!
        /// </summary>
        public SimpleFSLockFactory():this((System.IO.DirectoryInfo) null)
        {
        }

        /// <summary> Instantiate using the provided directory (as a File instance).</summary>
        /// <param name="lockDir">where lock files should be created.
        /// </param>
        public SimpleFSLockFactory(System.IO.DirectoryInfo lockDir)
        {
            LockDir = lockDir;
        }
        
        /// <summary> Instantiate using the provided directory name (String).</summary>
        /// <param name="lockDirName">where lock files should be created.
        /// </param>
        public SimpleFSLockFactory(System.String lockDirName)
            : this(new System.IO.DirectoryInfo(lockDirName))
        {
        }
        
        public override Lock MakeLock(System.String lockName)
        {
            if (internalLockPrefix != null)
            {
                lockName = internalLockPrefix + "-" + lockName;
            }
            return new SimpleFSLock(internalLockDir, lockName);
        }
        
        public override void  ClearLock(System.String lockName)
        {
            bool tmpBool;
            if (System.IO.File.Exists(internalLockDir.FullName))
                tmpBool = true;
            else
                tmpBool = System.IO.Directory.Exists(internalLockDir.FullName);
            if (tmpBool)
            {
                if (internalLockPrefix != null)
                {
                    lockName = internalLockPrefix + "-" + lockName;
                }
                System.IO.FileInfo lockFile = new System.IO.FileInfo(System.IO.Path.Combine(internalLockDir.FullName, lockName));
                bool tmpBool2;
                if (System.IO.File.Exists(lockFile.FullName))
                    tmpBool2 = true;
                else
                    tmpBool2 = System.IO.Directory.Exists(lockFile.FullName);
                bool tmpBool3;
                if (System.IO.File.Exists(lockFile.FullName))
                {
                    System.IO.File.Delete(lockFile.FullName);
                    tmpBool3 = true;
                }
                else if (System.IO.Directory.Exists(lockFile.FullName))
                {
                    System.IO.Directory.Delete(lockFile.FullName);
                    tmpBool3 = true;
                }
                else
                    tmpBool3 = false;
                if (tmpBool2 && !tmpBool3)
                {
                    throw new System.IO.IOException("Cannot delete " + lockFile);
                }
            }
        }
    }
    
    
    class SimpleFSLock:Lock
    {
        
        internal System.IO.FileInfo lockFile;
        internal System.IO.DirectoryInfo lockDir;

        [System.Obsolete("Use the constructor that takes a DirectoryInfo, this will be removed in the 3.0 release")]
        public SimpleFSLock(System.IO.FileInfo lockDir, System.String lockFileName) : this(new System.IO.DirectoryInfo(lockDir.FullName), lockFileName)
        {
        }

        public SimpleFSLock(System.IO.DirectoryInfo lockDir, System.String lockFileName)
        {
            this.lockDir = new System.IO.DirectoryInfo(lockDir.FullName);
            lockFile = new System.IO.FileInfo(System.IO.Path.Combine(lockDir.FullName, lockFileName));
        }
        
        public override bool Obtain()
        {
            
            // Ensure that lockDir exists and is a directory:
            bool tmpBool;
            if (System.IO.File.Exists(lockDir.FullName))
                tmpBool = true;
            else
                tmpBool = System.IO.Directory.Exists(lockDir.FullName);
            if (!tmpBool)
            {
                try
                {
                    System.IO.Directory.CreateDirectory(lockDir.FullName);
                }
                catch
                {
                    throw new System.IO.IOException("Cannot create directory: " + lockDir.FullName);
                }
            }
            else
            {
                try
                {
                     System.IO.Directory.Exists(lockDir.FullName);
                }
                catch
                {
                    throw new System.IO.IOException("Found regular file where directory expected: " + lockDir.FullName);
                }
            }

            if (lockFile.Exists)
            {
                return false;
            }
            else
            {
                System.IO.FileStream createdFile = lockFile.Create();
                createdFile.Close();
                return true;
            }
        }
        
        public override void  Release()
        {
            bool tmpBool;
            if (System.IO.File.Exists(lockFile.FullName))
                tmpBool = true;
            else
                tmpBool = System.IO.Directory.Exists(lockFile.FullName);
            bool tmpBool2;
            if (System.IO.File.Exists(lockFile.FullName))
            {
                System.IO.File.Delete(lockFile.FullName);
                tmpBool2 = true;
            }
            else if (System.IO.Directory.Exists(lockFile.FullName))
            {
                System.IO.Directory.Delete(lockFile.FullName);
                tmpBool2 = true;
            }
            else
                tmpBool2 = false;
            if (tmpBool && !tmpBool2)
                throw new LockReleaseFailedException("failed to delete " + lockFile);
        }
        
        public override bool IsLocked()
        {
            bool tmpBool;
            if (System.IO.File.Exists(lockFile.FullName))
                tmpBool = true;
            else
                tmpBool = System.IO.Directory.Exists(lockFile.FullName);
            return tmpBool;
        }
        
        public override System.String ToString()
        {
            return "SimpleFSLock@" + lockFile;
        }
    }
}