Tim Allison created IO-802:
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Summary: Restore threadlocal for skipfully() byte buffer
Key: IO-802
URL: https://issues.apache.org/jira/browse/IO-802
Project: Commons IO
Issue Type: Bug
Reporter: Tim Allison
Over on TIKA-4065, we found that trying to upgrade to commons-io 2.12.0 or
2.13.0 caused one of our unit tests to fail. We found that dropping
{{threadlocal}} on the buffer used in IOUtils.skipFully() in conjunction with
Java's InflaterInputStream was the cause of the problem.
Our unit test shows that running skipFully() on a stream and then reading gets
different results on the same underlying stream when running multithreaded.
This is really bad. It appears to be confined to InflaterInputStream...so not
a very common case.
On the [commons-io's user
list|https://lists.apache.org/thread/rxfyxqochnj7bw75nr2v7hf5qtkogx7d]
[~psteitz] observed that Java's InflaterInputStream expects read access to the
byte array passed in...so having multiple threads writing to the same static
(not-thread local) byte array is dangerous. The behavior of Java's
InflaterInputStream is surprising and not documented.
I have a demonstration of the problem here:
https://github.com/tballison/commons-io/blob/TIKA-4065/src/test/java/org/apache/commons/io/IOUtilsMultithreadedTest.java
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