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https://issues.apache.org/jira/browse/IO-871?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17938343#comment-17938343
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Éamonn McManus commented on IO-871:
-----------------------------------
OK, I can confirm that all of our tests work with the latest snapshot.
> 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
> Assignee: Gary D. Gregory
> Priority: Minor
> Fix For: 2.19.0
>
>
> 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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