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https://issues.apache.org/jira/browse/IO-726?focusedWorklogId=609879&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-609879
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ASF GitHub Bot logged work on IO-726:
-------------------------------------
Author: ASF GitHub Bot
Created on: 10/Jun/21 18:46
Start Date: 10/Jun/21 18:46
Worklog Time Spent: 10m
Work Description: shollander commented on a change in pull request #215:
URL: https://github.com/apache/commons-io/pull/215#discussion_r649437283
##########
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:
The number given is based on one use case where I used this code.
I will remove the performance claim since I don't have time to spend
developing benchmarks.
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Issue Time Tracking
-------------------
Worklog Id: (was: 609879)
Time Spent: 2h 40m (was: 2.5h)
> Add MemoryMappedInputStream
> ---------------------------
>
> Key: IO-726
> URL: https://issues.apache.org/jira/browse/IO-726
> Project: Commons IO
> Issue Type: New Feature
> Components: Streams/Writers
> Affects Versions: 2.8.0
> Reporter: S Hollander
> Priority: Major
> Fix For: 2.10.0
>
> Time Spent: 2h 40m
> Remaining Estimate: 0h
>
> A very useful tool for improving performance with disk-based IO is the use of
> memory mapped files. I propose an {{InputStream}} that provides a bridge
> between memory mapped files and the {{InputStream}} ecosystem.
> In my limited performance tests, the use of the MemoryMappedInputStream
> provided a 25% increase in throughput.
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