Add an nio mmap based Directory implementation.

git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@150538 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/lucene/store/MMapDirectory.java

@@ -0,0 +1,90 @@
+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.io.RandomAccessFile;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileChannel.MapMode;
+
+/** File-based {@link Directory} implementation that uses mmap for input.
+ *
+ * <p>To use this, invoke Java with the System property
+ * org.apache.lucene.FSDirectory.class set to
+ * org.apache.lucene.store.MMapDirectory.  This will cause {@link
+ * FSDirectory#getDirectory(File,boolean)} to return instances of this class.
+ *
+ * @author Doug Cutting
+ */
+public class MMapDirectory extends FSDirectory {
+
+  private class MMapIndexInput extends IndexInput {
+
+    private ByteBuffer buffer;
+    private RandomAccessFile file;
+    private long length;
+    private boolean isClone;
+
+    public MMapIndexInput(String path) throws IOException {
+      this.file = new RandomAccessFile(path, "r");
+      this.length = file.length();
+      this.buffer = file.getChannel().map(MapMode.READ_ONLY, 0, length);
+    }
+
+    public byte readByte() throws IOException {
+      return buffer.get();
+    }
+
+    public void readBytes(byte[] b, int offset, int len)
+      throws IOException {
+      buffer.get(b, offset, len);
+    }
+
+    public long getFilePointer() {
+      return buffer.position();
+    }
+
+    public void seek(long pos) throws IOException {
+      buffer.position((int)pos);
+    }
+
+    public long length() {
+      return length;
+    }
+
+    public Object clone() {
+      MMapIndexInput clone = (MMapIndexInput)super.clone();
+      clone.isClone = true;
+      clone.buffer = buffer.duplicate();
+      return clone;
+    }
+
+    public void close() throws IOException {
+      if (!isClone)
+        file.close();
+    }
+  }
+
+  private MMapDirectory() {}                      // no public ctor
+
+  public IndexInput openInput(String name) throws IOException {
+    return new MMapIndexInput(new File(getFile(), name).getPath());
+  }
+}
+