Hmmmm. "Flakey wireless LAN".... ?
Surely wifi (or any LAN tech for that matter) has mechanisms built in to the protocol to ensure this sort of thing does not occur.... certainly even with the flakiest of wifi connections I have never experienced corruption. The wifi connection is either made, however slowly as a result of the flakiness, or not made at all. Are you positive that the "corruption" is not occurring directly in the output of the remote server, rather than in the communication of the data ? Because if that's the case then checksuming will of course be a waste of time -----Original Message----- From: delphi-boun...@delphi.org.nz [mailto:delphi-boun...@delphi.org.nz] On Behalf Of Todd Sent: Monday, 17 January 2011 14:22 To: NZ Borland Developers Group - Delphi List Subject: Re: [DUG] Validating CDS files Hi Matthew It sounds like comparing a MD5 hash of the CDS file prior to sending and subsequent to receiving the data stream would provide a sufficient check on its integrity. Todd. > Hi Todd, > > The ClientDatasets initially get populated via a remote server, and it is > this process which in rare cases causes the corruption (e.g. customer on > flakey wireless lan or similar). > > Longterm we will replace this mechanism so the dataset is populated server > side and send back with a hash which will maintain integrity. > > For the moment, we are stuck with a mechanism which populates this cds > data and then writes to file. > > Appending some metadata at this point is a valid option. Ill test and see > if it circumvents the issue. The main issue though is that I'm not sure if > the ClientDataset at this point knows that the data is corrupt, and > therefore we could be exporting a corrupt data chunk packed with some > metadata, which does not help. > > Thats why we really need some protection on load. > > Cheers, > > Matt. > > > > >> Hi Matthew >> >> Are the CDS files being stored as disk files or in a database? How are >> they being corrupted? Faulty back up media? Perhaps you could add some >> meta-data to each file as it is saved. >> >> Todd. >> >>> The driver for the question, is that we have some application client >>> datasets which are put into a defaulted state if a corrupt cds file is >>> loaded. >>> >>> Yes with XML, we can just validate the XML, but we use the binary format >>> so that solution does not apply. >>> >>> At present we basically have two solutions. >>> >>> 1. Load into a test clientdataset as suggested by Alistair. This is a >>> valid solution but does add considerable load time into the startup. >>> >>> 2. Can load into application clientdatasets, and dispose and reload if >>> error encountered. This is ok also but does require additional loading >>> in >>> case of error. >>> >>> What I'm really after is a file level test to check that file should >>> even >>> be attempted. e.g. open file stream seek start and seek end and check a >>> couple of bytes... that type of thing. >>> >>> Matt. >>> >>> >>> >>> >>> >>>> What does "validate" mean for a CDS file ? >>>> >>>> For XML it obviously/intuitively means "is a valid XML representation >>>> of a >>>> CDS file" but for a CDS file, if you dumped it from a client data set >>>> in >>>> the >>>> first place, what additional validation would be needed to ensure that >>>> it >>>> is >>>> a CDS file ? >>>> >>>> >>>> -----Original Message----- >>>> From: delphi-boun...@delphi.org.nz >>>> [mailto:delphi-boun...@delphi.org.nz] >>>> On >>>> Behalf Of Matthew Comb >>>> Sent: Monday, 17 January 2011 10:27 >>>> To: NZ Borland Developers Group - Delphi List >>>> Subject: Re: [DUG] Validating CDS files >>>> >>>> Hey Cam, for space size reasons, we're using the CDS format not the XML >>>> format as the files get pretty large. >>>> >>>> Matt >>>> >>>> >>>> >>>>> If you have dumped the CDS as XML then you can validate it using XSD. >>>>> I >>>>> haven't come across a schema for it but it shouldn't be hard to make. >>>>> >>>>> Cameron Hart | Development Manager | Flow Software Limited >>>>> P: +64 9 476 3569 x910 | M: +64 21 222 3569 | E: >>>>> cameron.h...@flowsoftware.co.nz >>>>> PO Box 305-237, Triton Plaza, Auckland 0757, New Zealand | >>>>> www.flowsoftware.co.nz >>>>> >>>>> This message is intended for the addressee named above. It may contain >>>>> privileged or confidential information. If you are not the intended >>>>> recipient of this message you must not use, copy, distribute or >>>>> disclose >>>>> it to anyone. >>>>> >>>>> Please consider the environment before printing this email >>>>> >>>>> -----Original Message----- >>>>> From: delphi-boun...@delphi.org.nz >>>>> [mailto:delphi-boun...@delphi.org.nz] >>>>> On Behalf Of Matthew Comb >>>>> Sent: Monday, 17 January 2011 10:03 a.m. >>>>> To: NZ Borland Developers Group - Delphi List >>>>> Cc: NZ Borland Developers Group - Delphi List >>>>> Subject: [DUG] Validating CDS files >>>>> >>>>> Does anyone know if there is a way to Validate a CDS file (midas) >>>>> before >>>>> attempting to load it into the dataset ? >>>>> >>>>> Matt >>>>> >>>>> _______________________________________________ >>>>> NZ Borland Developers Group - Delphi mailing list >>>>> Post: delphi@delphi.org.nz >>>>> Admin: http://delphi.org.nz/mailman/listinfo/delphi >>>>> Unsubscribe: send an email to delphi-requ...@delphi.org.nz with >>>>> Subject: >>>>> unsubscribe >>>>> >>>>> _______________________________________________ >>>>> NZ Borland Developers Group - Delphi mailing list >>>>> Post: delphi@delphi.org.nz >>>>> Admin: http://delphi.org.nz/mailman/listinfo/delphi >>>>> Unsubscribe: send an email to delphi-requ...@delphi.org.nz with >>>>> Subject: >>>>> unsubscribe >>>>> >>>>> >>>>> >>>> _______________________________________________ >>>> NZ Borland Developers Group - Delphi mailing list >>>> Post: delphi@delphi.org.nz >>>> Admin: http://delphi.org.nz/mailman/listinfo/delphi >>>> Unsubscribe: send an email to delphi-requ...@delphi.org.nz with >>>> Subject: >>>> unsubscribe >>>> >>>> _______________________________________________ >>>> NZ Borland Developers Group - Delphi mailing list >>>> Post: delphi@delphi.org.nz >>>> Admin: http://delphi.org.nz/mailman/listinfo/delphi >>>> Unsubscribe: send an email to delphi-requ...@delphi.org.nz with >>>> Subject: >>>> unsubscribe >>>> >>>> >>>> >>> _______________________________________________ >>> NZ Borland Developers Group - Delphi mailing list >>> Post: delphi@delphi.org.nz >>> Admin: http://delphi.org.nz/mailman/listinfo/delphi >>> Unsubscribe: send an email to delphi-requ...@delphi.org.nz with Subject: >>> unsubscribe >>> >>> >> _______________________________________________ >> NZ Borland Developers Group - Delphi mailing list >> Post: delphi@delphi.org.nz >> Admin: http://delphi.org.nz/mailman/listinfo/delphi >> Unsubscribe: send an email to delphi-requ...@delphi.org.nz with Subject: >> unsubscribe >> >> > > _______________________________________________ > NZ Borland Developers Group - Delphi mailing list > Post: delphi@delphi.org.nz > Admin: http://delphi.org.nz/mailman/listinfo/delphi > Unsubscribe: send an email to delphi-requ...@delphi.org.nz with Subject: unsubscribe > _______________________________________________ NZ Borland Developers Group - Delphi mailing list Post: delphi@delphi.org.nz Admin: http://delphi.org.nz/mailman/listinfo/delphi Unsubscribe: send an email to delphi-requ...@delphi.org.nz with Subject: unsubscribe _______________________________________________ NZ Borland Developers Group - Delphi mailing list Post: delphi@delphi.org.nz Admin: http://delphi.org.nz/mailman/listinfo/delphi Unsubscribe: send an email to delphi-requ...@delphi.org.nz with Subject: unsubscribe
