Re: [Quickfix-developers] Checksum / Charset encoding problem

[Lin L. <le...@gm...>]

Hi,Lalonde

8=青


using getBytes()
56 + 61 - 57 - 32 + 1 = 29
~~~~~~~~~~~~~~~~~~~~
Should not has negative number in above equality.
I think it like blown:
56 + 61 +199 +244 + 1 = 561

Because I use unsigned byte value in it.


Lejiang




On 7/20/06, Lalonde, Francis <fra...@cg...> wrote:
>
>  Hello Lin,
>
> Interesting question!
>
> The problem is that QuickFIX uses charAt() to calculate
> the message checksum and getBytes() to fill network buffer but the results
> dont match.
>
> I looked at the code, and I think my solution should work with double-byte
> charset, because all it does is use getBytes() in both places.
>
> So in FIX checksum
>
>  8=青

>
> using charAt() :
>
> 56 + 61 + 38738 + 1 = 38856
>
> using getBytes()
>
> 56 + 61 - 57 - 32 + 1 = 29
>
>  ------------------------------
> *From:* Lin Lejiang [mailto:le...@gm...]
> *Sent:* Wednesday, July 19, 2006 11:38 AM
> *To:* Lalonde, Francis
> *Cc:* qui...@li...
> *Subject:* Re: [Quickfix-developers] Checksum / Charset encoding problem
>
>
>  Hi,Lalonde
> I get the same problem with you.I use QFJ in GBK encoding platform.
> You solution will not work in double byte charset.e.g. GBK.Is it?
> In FIX document,checksum function will be:
>
> char *GenerateCheckSum( char *buf, long bufLen )
>
> {
>
>        static char tmpBuf[ 4 ];
>
>        long idx;
>
>        unsigned int cks;
>
>
>
>        for( idx = 0L, cks = 0; idx < bufLen; cks += (unsigned int)buf[
> idx++ ] );
>
>        sprintf( tmpBuf, "%03d", (unsigned int)( cks % 256 ) );
>
>        return( tmpBuf );
>
> }
>
> In GBK encoding:
> "青".charAt(0)=38738
> "青".getBytes()[0]=-57
> "青".getBytes()[1]=-32
>
> The chk must be added with unsigned int or byte.
> So in java:
> chk = ((int)"青".getBytes()[0] )& 0xFF + ((int)"青".getBytes()[1] )& 0xFF
>
>
> Do you think so?
>
>
> Lejiang
>
>
>
> On 7/11/06, Lalonde, Francis <fra...@cg...> wrote:
> >
> > QuickFIX Documentation: http://www.quickfixengine.org/quickfix/doc/html/index.html
> >
> > QuickFIX Support: http://www.quickfixengine.org/services.html
> >
> >
> >
> >
> >  I haven't found references to this problem in the wiki or elsewhere, so
> > I just wanted to share my thoughts.
> >
> > I've been having checksum problems when trying to send FIX messages
> > having an XML payload. The FIX server I was communicating with (an instance
> > of the Cameron FIX engine) would report bad checksums ont those messages
> > containing XML, but not on other messages (Logon, Heartbeat, etc)
> >
> > I wrote a parallel program to double-check the checksums of the messages
> > waiting in the QuickFIX queue (by parsing the .body file) just to make sure
> > that the problem was really on my side, and it was.
> >
> > I traced the problem down to QuickFIX way of handling the charset
> > encoding of the String fields. I fixed the problem by changing the
> > Field.getTotal() method from
> >
> > *
> >
> > int
> > *getTotal() {
> >
> >     calculate();
> >
> > *    int* sum = 0;
> >
> > *    for* (*int* i = 0; i < data.length(); i++) {
> >
> >         sum += data.charAt(i);
> >
> >     }
> >
> > *    return* sum + 1;
> >
> > }
> >
> > to
> > *
> >
> > int
> > *getTotal() {
> >
> >     calculate();
> >
> > *    int* sum = 1;
> >
> > *    byte*[] bytes = data.getBytes();
> >
> > *    for* (*int* i = 0; i < bytes. length; i++) {
> >
> >         sum += bytes[i];
> >
> >     }
> >
> > *    return* sum;
> >
> > }
> >
> > It seems that charAt(i) and getBytes()[i] dont always return the same
> > byte value, and since the MINA message encoder uses getBytes() to prepare
> > the wire data, this method should also be used when computing the checksum
> > to ensure accurate results. Also, I think the checksumming operation should
> > probably moved to the encoding stage, to eliminate the redundancy of the
> > relatively expensive getByte() which gets actually get called twice for each
> > character in the message, but this required more extensive modifications so
> > I left at this for now.
> >
> >  Francis Lalonde
> > Treasury Services
> > CGI
> >
> >
> >
> >
> >
> > -------------------------------------------------------------------------
> > Using Tomcat but need to do more? Need to support web services,
> > security?
> > Get stuff done quickly with pre-integrated technology to make your job
> > easier
> > Download IBM WebSphere Application Server v.1.0.1 based on Apache
> > Geronimo
> > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
> >
> >
> > _______________________________________________
> > Quickfix-developers mailing list
> > Qui...@li...
> > https://lists.sourceforge.net/lists/listinfo/quickfix-developers
> >
> >
>
>
> --
> Lin Lejiang
>



-- 
Lin Lejiang