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From Mark Hindess <mark.hind...@googlemail.com>
Subject Re: [classlib] java.io.DataOutputStream behaviour doesn't match RI
Date Sun, 13 Sep 2009 08:07:31 GMT

In message <200909112249.n8BMnnZB016878@d06av04.portsmouth.uk.ibm.com>,
Mark Hindess writes:
> 
> In message <4AAACFCE.5090809@gmail.com>, Tim Ellison writes:
> >
> > On 11/Sep/2009 23:13, Mark Hindess wrote:
> > > I am trying to work through the JDWP java6 branch test failures
> > > (so is Oliver).  I see quite a lot of intermittent failures on
> > > Linux[0].  I think they are mostly caused by failures at the time
> > > when the socket used for synchronising the debuggee/debugger
> > > is being closed.  The sychronisation is simply one end calling
> > > "DataOutputStream.writeUTF("continue"); DataOutputStream.flush();" and
> > > the other end trying to do DataInputStream.readUTF().
> > > 
> > > When running on the RI, the tests pass consistently.  Strace of the RI
> > > shows the writeUTF making syscalls like:
> > > 
> > >   send(10, "\0\10continue", 10, 0) = 10
> > >   close(10)                        = 0
> > > 
> > > where as our implementation does:
> > > 
> > >   send(58, "\0\10", 2, 0)    = 2
> > >   send(58, "continue", 8, 0) = 8
> > >   close(58)                  = 0
> > > 
> > > Examining the packet dump for the socket shows a packet containing the
> > > length ('\0\10') followed by a RST packet as the socket is closed but no
> > > packet containing the "continue" text.  So, the "continue" is lost with
> > > the result that the other end reads the length then loops waiting for
> > > the message until the test timeout is reached.[1]
> > > 
> > > I think it would probably be useful if we fixed our implementation to
> > > have the same behaviour as the RI.
> > 
> > +1
> > 
> > I'm happy to take a look at that if you want.
> 
> Well, just doing the obvious thing of re-writing writeUTF by moving
> the code from writeUTFBytes (and making utfBytes two bytes larger to
> insert the length) into writeUTF seems to fix at least some of the
> intermittent failures for me.  (I've appended the patch but it doesn't
> really show what I did particularly well.) But I've not run the luni
> tests on this change yet and I need sleep now.

I've done a few jdwp test runs now and this approach definitely improves
stability quite a bit.  Unfortunately ObjectOutputStream uses the
writeUTFBytes method that my patch removes so it needs more work.  I
wonder whether the ObjectOutputStream implementation suffers from the
same issue.

-Mark.

> And I still want to figure out why the test framework missed the close.
> 
> Regards,
>  Mark.
> 
> > > Regards,
> > >  Mark.
> > > 
> > > [0] I'm using org.apache.harmony.jpda.tests.jdwp.MultiSession.RefTypeIDTe
> st
> > >     for testing but there are plenty of intermittently failing tests to
> > >     choose from.
> > > 
> > > [1] I wonder why doesn't it see the socket close and bail out?  This is
> > >     probably another bug (perhaps with the framework).
> 
> Index: modules/luni/src/main/java/java/io/DataOutputStream.java
> ===================================================================
> --- modules/luni/src/main/java/java/io/DataOutputStream.java	(revision 81373
> 9)
> +++ modules/luni/src/main/java/java/io/DataOutputStream.java	(working copy)
> @@ -314,30 +314,12 @@
>          if (utfCount > 65535) {
>              throw new UTFDataFormatException(Msg.getString("K0068")); //$NON
> -NLS-1$
>          }
> -        writeShort((int) utfCount);
> -        writeUTFBytes(str, utfCount);
> -    }
> -
> -    long countUTFBytes(String str) {
> -        int utfCount = 0, length = str.length();
> -        for (int i = 0; i < length; i++) {
> -            int charValue = str.charAt(i);
> -            if (charValue > 0 && charValue <= 127) {
> -                utfCount++;
> -            } else if (charValue <= 2047) {
> -                utfCount += 2;
> -            } else {
> -                utfCount += 3;
> -            }
> -        }
> -        return utfCount;
> -    }
> -
> -    void writeUTFBytes(String str, long count) throws IOException {
> -        int size = (int) count;
> +        int size = (int) utfCount;
>          int length = str.length();
> -        byte[] utfBytes = new byte[size];
> +        byte[] utfBytes = new byte[size+2];
>          int utfIndex = 0;
> +        utfBytes[utfIndex++] = (byte) (size >> 8);
> +        utfBytes[utfIndex++] = (byte) size;
>          for (int i = 0; i < length; i++) {
>              int charValue = str.charAt(i);
>              if (charValue > 0 && charValue <= 127) {
> @@ -353,4 +335,19 @@
>          }
>          write(utfBytes, 0, utfIndex);
>      }
> +
> +    long countUTFBytes(String str) {
> +        int utfCount = 0, length = str.length();
> +        for (int i = 0; i < length; i++) {
> +            int charValue = str.charAt(i);
> +            if (charValue > 0 && charValue <= 127) {
> +                utfCount++;
> +            } else if (charValue <= 2047) {
> +                utfCount += 2;
> +            } else {
> +                utfCount += 3;
> +            }
> +        }
> +        return utfCount;
> +    }
>  }
> 



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