[vtkusers] string compare bug?

[Jeff Lee]

Kevin Wright wrote:

> At 04:25 PM 10/7/2002 -0400, you wrote:
>
>> Are you using vtkSocketController/vtkSocketCommunicator?  These 
>> objects already do this under the hood.
>> -Jeff
>
>
> No, I'm tying it in with some other code here.  Are you saying that 
> vtkSocketController/Communicator addresses the bug that I'm talking 
> about, or that it provides the same functionality? 


those classes provide the same functionality, and use a very similar 
approach.  I'm not sure what you are seeing is a bug per-se - does your 
Irix/Linux build do the same thing?  I agree that the string compare 
could be expensive, but the dataset update could be even more so.  I 
have been told that the data readers/writers are going to change in the 
near future to xml anyway, but it would be good to know if this is just 
a windows problem.  I have been using the socketcommunicator for quite 
some time and it doesn't exhibit these symptoms.  If you have some 
sample code, it might be worth putting up on the list so people can test 
it...
-Jeff

>
>
> Kevin.
>
>
>> Kevin Wright wrote:
>>
>>> I just tracked down what looks like an odd bug, and I was wondering 
>>> if anyone out there had any insight.
>>>
>>> I'm using a vtkPolyDataReader object to field incoming polydata 
>>> definitions through a socket.  I do this by reading the polydata 
>>> from the socket into a string, then using the input string in the 
>>> vtkDataReader.
>>>
>>> Everything generally worked fine, except in some cases the pipeline 
>>> would not update when new data came down the socket.  Eventually I 
>>> tracked the problem down to vtkDataReader::SetInputString which, 
>>> before assigning the string, does a string compare between the old 
>>> and new string.
>>>
>>> When the new and old datasets were very similar (usually identical 
>>> geometry, slightly changed scalar values) the strncmp would return a 
>>> match.  The string length was correct, and once the string compare 
>>> was removed, everything worked fine.
>>>
>>> I'm working on a Windows 2000 machine with VC++ 6.0.  I'm about to 
>>> try the same thing on IRIX and Linux to see what happens, but I was 
>>> wondering:
>>>
>>> 1. Has anyone seen this kind of behavior before?
>>> 2. Should the string compare really be there at all, given that 
>>> these strings could be very long?
>>>
>>> Regards,
>>> Kevin.
>>>
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