There are two ways to fix this problem:
1. Add a read-only flag in FileDescriptor. The default value is false. Set
the flag to true in FileInputStream and RandomeAccessFile("r").
2. Determine the fd in native code whether the fd is read-only.
Solution 1 judges the fd in java code, but has to remove "native"
from FileDescriptor#sync() signature. While solution 2 seems nature, and
solves the problem thoroughly, but requires more codes. If we adopt solution
2, we should add a new portable native mehtod like isReadOnly(int fd). Where
should we put the method? in port? or OSFileSystemWin32/Linux? Any
suggestions and comments?
Thanks!
On 9/19/06, Andrew Zhang <[EMAIL PROTECTED]> wrote:
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 <[EMAIL PROTECTED]> wrote:
>
> On 9/18/06, Andrew Zhang <[EMAIL PROTECTED]> wrote:
> > On 9/18/06, Richard Liang <[EMAIL PROTECTED]> 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: [EMAIL PROTECTED]
> > > For additional commands, e-mail:
> [EMAIL PROTECTED]
> > >
> > >
> >
> >
> > --
> > 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: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
>
--
Andrew Zhang
China Software Development Lab, IBM
--
Best regards,
Andrew Zhang
