Éamonn McManus created IO-871:
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Summary: IOUtils.contentEquals is incorrect when
InputStream.available under-reports
Key: IO-871
URL: https://issues.apache.org/jira/browse/IO-871
Project: Commons IO
Issue Type: Bug
Components: Utilities
Affects Versions: 2.19.0
Reporter: Éamonn McManus
A [recent
change|https://github.com/apache/commons-io/commit/c832eb20796b25d8ee2437a8663616b1112cd7bd]
to IOUtils.contentEquals(InputStream,InputStream) introduced a bug when at
least one of the InputStream instances under-reports the number of available
bytes. That is completely allowed by the contract of InputStream. I think the
underlying problem may be [this
line|https://github.com/apache/commons-io/blob/0d41d2fd958f28a0c4eb21afb6f34be8efa0e4fb/src/main/java/org/apache/commons/io/channels/FileChannels.java#L94]
in FileChannels. There's no requirement for a ReadableByteChannel.read to
return all available bytes, and therefore it is possible for one of the two
reads being compared to be shorter than the other, even though the contents of
the two channels are in fact equal.
This problem showed up when importing the latest source snapshot to Google's
internal repository and running all of Google's tests against it. Here is a
simple repro:
{code:java}
assertThat(
IOUtils.contentEquals(
new ByteArrayInputStream("ab".getBytes()),
new SequenceInputStream(
new ByteArrayInputStream("a".getBytes()),
new ByteArrayInputStream("b".getBytes()))))
.isTrue(); {code}
The assertion passes before this change and fails after it.
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