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The source code

package org.apache.lucene.store;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed 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.
 */

import java.io.IOException;
import java.io.File;
import java.util.Hashtable;
import java.util.Enumeration;

import org.apache.lucene.store.Directory;
import org.apache.lucene.store.InputStream;
import org.apache.lucene.store.OutputStream;

/**
 * A memory-resident {@link Directory} implementation.
 *
 * @version $Id: RAMDirectory.java,v 1.15 2004/05/09 12:41:47 ehatcher Exp $
 */
public final class RAMDirectory extends Directory {
  Hashtable files = new Hashtable();

  /** Constructs an empty {@link Directory}. */
  public RAMDirectory() {
  }

  /**
   * Creates a new RAMDirectory instance from a different
   * Directory implementation.  This can be used to load
   * a disk-based index into memory.
   * 

* This should be used only with indices that can fit into memory. * * @param dir a Directory value * @exception IOException if an error occurs */ public RAMDirectory(Directory dir) throws IOException { this(dir, false); } private RAMDirectory(Directory dir, boolean closeDir) throws IOException { final String[] files = dir.list(); for (int i = 0; i < files.length; i++) { // make place on ram disk OutputStream os = createFile(files[i]); // read current file InputStream is = dir.openFile(files[i]); // and copy to ram disk int len = (int) is.length(); byte[] buf = new byte[len]; is.readBytes(buf, 0, len); os.writeBytes(buf, len); // graceful cleanup is.close(); os.close(); } if(closeDir) dir.close(); } /** * Creates a new RAMDirectory instance from the {@link FSDirectory}. * * @param dir a File specifying the index directory */ public RAMDirectory(File dir) throws IOException { this(FSDirectory.getDirectory(dir, false), true); } /** * Creates a new RAMDirectory instance from the {@link FSDirectory}. * * @param dir a String specifying the full index directory path */ public RAMDirectory(String dir) throws IOException { this(FSDirectory.getDirectory(dir, false), true); } /** Returns an array of strings, one for each file in the directory. */ public final String[] list() { String[] result = new String[files.size()]; int i = 0; Enumeration names = files.keys(); while (names.hasMoreElements()) result[i++] = (String)names.nextElement(); return result; } /** Returns true iff the named file exists in this directory. */ public final boolean fileExists(String name) { RAMFile file = (RAMFile)files.get(name); return file != null; } /** Returns the time the named file was last modified. */ public final long fileModified(String name) throws IOException { RAMFile file = (RAMFile)files.get(name); return file.lastModified; } /** Set the modified time of an existing file to now. */ public void touchFile(String name) throws IOException { // final boolean MONITOR = false; RAMFile file = (RAMFile)files.get(name); long ts2, ts1 = System.currentTimeMillis(); do { try { Thread.sleep(0, 1); } catch (InterruptedException e) {} ts2 = System.currentTimeMillis(); // if (MONITOR) { // count++; // } } while(ts1 == ts2); file.lastModified = ts2; // if (MONITOR) // System.out.println("SLEEP COUNT: " + count); } /** Returns the length in bytes of a file in the directory. */ public final long fileLength(String name) { RAMFile file = (RAMFile)files.get(name); return file.length; } /** Removes an existing file in the directory. */ public final void deleteFile(String name) { files.remove(name); } /** Removes an existing file in the directory. */ public final void renameFile(String from, String to) { RAMFile file = (RAMFile)files.get(from); files.remove(from); files.put(to, file); } /** Creates a new, empty file in the directory with the given name. Returns a stream writing this file. */ public final OutputStream createFile(String name) { RAMFile file = new RAMFile(); files.put(name, file); return new RAMOutputStream(file); } /** Returns a stream reading an existing file. */ public final InputStream openFile(String name) { RAMFile file = (RAMFile)files.get(name); return new RAMInputStream(file); } /** Construct a {@link Lock}. * @param name the name of the lock file */ public final Lock makeLock(final String name) { return new Lock() { public boolean obtain() throws IOException { synchronized (files) { if (!fileExists(name)) { createFile(name).close(); return true; } return false; } } public void release() { deleteFile(name); } public boolean isLocked() { return fileExists(name); } }; } /** Closes the store to future operations. */ public final void close() { } }

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