[GitHub] [commons-io] garydgregory commented on a change in pull request #215: IO-726 Add MemoryMappedInputStream.

[GitBox <gi...@apache.org>]

garydgregory commented on a change in pull request #215:
URL: https://github.com/apache/commons-io/pull/215#discussion_r646559878



##########
File path: src/main/java/org/apache/commons/io/input/MemoryMappedFileInputStream.java
##########
@@ -0,0 +1,169 @@
+/*
+ * 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.
+ */
+package org.apache.commons.io.input;
+
+import static org.apache.commons.io.IOUtils.EOF;
+
+import java.io.BufferedInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileChannel.MapMode;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+
+import org.apache.commons.io.ByteBufferCleaner;
+
+/**
+ * An {@link InputStream} that utilizes memory mapped files to improve
+ * performance. A sliding window of the file is mapped to memory to avoid
+ * mapping the entire file to memory at one time. The size of the sliding buffer
+ * is user configurable.
+ * 
+ * For most operating systems, mapping a file into memory is more expensive than
+ * reading or writing a few tens of kilobytes of data. From the standpoint of
+ * performance it is generally only worth mapping relatively large files into
+ * memory. Use of this class can provide approximately a 25% increase in
+ * throughput when reading large files. <br>

Review comment:
       I would not make any performance claims without backing it up with evidence like a test anyone can run on their combination of OS/JRE/file. IOW, provide a test where the user can specify the file size in a sys prop or command line for example.




-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: issues-unsubscribe@commons.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org