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From "Andrew Zhang" <zhanghuang...@gmail.com>
Subject Re: [classlib][io][nio] Sync issue of java.io.FileOutputStream and java.nio.channels.FileChannel
Date Tue, 19 Sep 2006 06:28:35 GMT
I just found another bug of sync. Harmony throws SyncFailedException when fd
is read-only while RI returns silently. Spec doesn't explictly describe the
behaviour in such case[1]. But, it seems intended behaviour of RI, because
it requires additional check before invoke os sync. Following test
reproduces the bug:

    public void testSyncReadOnly() throws Exception {
        String TESTFILE = "tempFile";
        try {
            FileOutputStream fos = new FileOutputStream(TESTFILE);
            fos.write("something".getBytes());
            fos.close();

            RandomAccessFile raf = new RandomAccessFile(TESTFILE, "rw");
            raf.getFD().sync();
            raf.close();

            FileInputStream fis = new FileInputStream(TESTFILE);
            fis.getFD().sync();
            fis.close();
        } finally {
            new File(TESTFILE).delete();
        }
    }

I'll file a JIRA to record this bug soon!
[1] "SyncFailedException - Thrown when the buffers cannot be flushed, or
because the system cannot guarantee that all the buffers have been
synchronized with physical media."


On 9/19/06, Richard Liang <richard.liangyx@gmail.com> wrote:
>
> On 9/18/06, Andrew Zhang <zhanghuangzhu@gmail.com> wrote:
> > On 9/18/06, Richard Liang <richard.liangyx@gmail.com> wrote:
> > >
> > > Hello,
> > >
> > > One Apache Derby test[1] fails on Harmony. It seems that RI always
> > > sync the FileOutputStream and FileChannel after each "write", which is
> > > different from Harmony. But there is no explicit description in Java
> > > Spec. Shall we follow RI? Thanks a lot.
> > >
> > > The following test cases could demonstrate this issue.
> > >
> > >    public void testFile() {
> > >        File derbyLog = new File("d:\\", "derby1.log");
> > >
> > >        try {
> > >            FileOutputStream fos = new FileOutputStream(derbyLog);
> > >            fos.write(0x41);
> > >            assertEquals(1, derbyLog.length());
> > >        } catch (Exception e) {
> > >            e.printStackTrace();
> > >        }
> > >    }
> > >
> > >    public void testFileChannel() {
> > >        File derbyLog = new File("d:\\", "derby2.log");
> > >
> > >        try {
> > >            FileOutputStream fos = new FileOutputStream(derbyLog);
> > >            FileChannel fc = fos.getChannel();
> > >            fc.write(ByteBuffer.wrap(new byte[]{0x41, 0x42}));
> > >            assertEquals(2, derbyLog.length());
> > >        } catch (Exception e) {
> > >            e.printStackTrace();
> > >        }
> > >    }
> >
> >
> > Interesting. I think we'd better follow RI although it's implementation
> > dependent. Otherwise, it breaks existing application.
> >
> > To make test more interesting, I wrote a similar test:
> >
> >
> >  public void testFile() throws Exception {
> >         File derbyLog = File.createTempFile("test", "log");
> >         derbyLog.deleteOnExit();
> >         RandomAccessFile fos = new RandomAccessFile(derbyLog, "rws");
> >         for (int i = 0; i < 1000; i++) {
> >             fos.write(0x41);
> >             assertEquals(1 + i, derbyLog.length());
> >         }
> >
> >  }
> >
> > Run it and you'll be surprised. :-)
>
> Wow! It tooks RI 0.381 seconds, while 21.761 seconds for Harmony. We
> shall improve our performance!
>
> Let's have a more further study about this issue.
>
> >
> > [1]
> > >
> http://svn.apache.org/viewvc/db/derby/code/trunk/java/testing/org/apache/derbyTesting/functionTests/tests/lang/logStream.java?view=co
> > > --
> > > Richard Liang
> > > China Development Lab, IBM
> > >
> > > ---------------------------------------------------------------------
> > > Terms of use : http://incubator.apache.org/harmony/mailing.html
> > > To unsubscribe, e-mail: harmony-dev-unsubscribe@incubator.apache.org
> > > For additional commands, e-mail: harmony-dev-help@incubator.apache.org
> > >
> > >
> >
> >
> > --
> > Andrew Zhang
> > China Software Development Lab, IBM
> >
> >
>
>
> --
> Richard Liang
> China Development Lab, IBM
>
> ---------------------------------------------------------------------
> Terms of use : http://incubator.apache.org/harmony/mailing.html
> To unsubscribe, e-mail: harmony-dev-unsubscribe@incubator.apache.org
> For additional commands, e-mail: harmony-dev-help@incubator.apache.org
>
>


-- 
Andrew Zhang
China Software Development Lab, IBM

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