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From "Richard Liang" <richard.lian...@gmail.com>
Subject Re: [classlib][io][nio] Sync issue of java.io.FileOutputStream and java.nio.channels.FileChannel
Date Tue, 19 Sep 2006 02:53:30 GMT
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
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> >
> >
>
>
> --
> Andrew Zhang
> China Software Development Lab, IBM
>
>


-- 
Richard Liang
China Development Lab, IBM

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