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

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

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
>
>
>
>
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-- 
Lin Lejiang