[
https://issues.apache.org/jira/browse/IO-871?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Éamonn McManus reopened IO-871:
-------------------------------
This issue may have been resolved, but I'm reopening it until I can verify.
(This involves a long test run that may not complete before tomorrow.)
I accidentally continued the discussion on IO-866. This is a copy of the
exchange there between [~ggregory] and me.
"""
[~eamonnmcmanus] added a comment - 2 days ago
Unfortunately the [recent
fix|https://github.com/apache/commons-io/commit/7815650ada4f27dc72c8c470d626481282b13dab]
does not work. Google's tests reveal a failure, which I have boiled down to
this repro:
{code:java}
byte[] prefix = new byte[32];
byte[] suffix = new byte[2];
byte[] fileContents = "someTexts".getBytes();
Files.write(testFile.toPath(), fileContents);
byte[] expected = new byte[prefix.length + fileContents.length +
suffix.length];
System.arraycopy(prefix, 0, expected, 0, prefix.length);
System.arraycopy(fileContents, 0, expected, prefix.length,
fileContents.length);
System.arraycopy(suffix, 0, expected, prefix.length +
fileContents.length, suffix.length);
assertTrue(IOUtils.contentEquals(
new ByteArrayInputStream(expected),
new SequenceInputStream(
Collections.enumeration(
Arrays.asList(
new ByteArrayInputStream(prefix),
new FileInputStream(testFile),
new ByteArrayInputStream(suffix)))))); {code}
The assertion passes if I replace the implementation of IOUtils.contentEquals
with a simple loop that reads one byte from each stream until finding a
mismatch or EOF, but it fails with the current snapshot implementation.
This is just my opinion, but the logic of the new
[FileChannels.contentEquals|https://github.com/apache/commons-io/blob/c2e18c6d02f07c7466b29caeb5ac94aa04c4957d/src/main/java/org/apache/commons/io/channels/FileChannels.java#L61]
method seems ferociously complicated and I wonder whether a simpler if less
efficient approach might be better. Perhaps anyway the established
IOUtils.contentEquals method could revert to its [old
implementation|https://github.com/apache/commons-io/blob/1d2019f2a32fc5388e955c5a3a7fa4f236538d4a/src/main/java/org/apache/commons/io/IOUtils.java#L906]?
[~ggregory] added a comment - 2 days ago
Hello [~eamonnmcmanus]
Thank you for the additional feedback.
We can revert to the old implementation if need be, but this does not solve the
issue of fixing {{{}FileChannels.contentEquals(){}}}.
If you can find a better way to implement {{{}FileChannels.contentEquals(){}}},
feel free to provide it :)
So for now, I'll incorporate this new test and see how to fix that method.
[~ggregory] added a comment - Yesterday
Hello [~eamonnmcmanus]
I fixed your most recent use case. Please test git master or a build from our
snapshot repository
[https://repository.apache.org/content/repositories/snapshots]
"""
> 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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