[ubuntu-uk] Reverse engineering data files

Gareth France gareth.france at cliftonts.co.uk
Mon Nov 24 16:25:09 UTC 2014

I shared an example file in my initial post.


However I am holding fire for the moment while I discuss with the 
software designers the possibility of being given the design specs and 
signing a non-disclosure agreement.

On 24/11/14 16:20, James Tait wrote:
> Hash: SHA1
> On 23/11/14 19:23, Gareth France wrote:
>> It is readable, but no more so than if you just load it into perl
>> using binmode. I'm currently struggling with identifying the
>> different fields within the data. I've been plucking them out
>> manually which is fine for the first half then I find some of them
>> are variable length and I have no way of identifying where they
>> start.
> Variable length fields are often prefixed with a field length, so the
> software knows how many bytes to read, or null-terminated, so the
> software reads until it reaches a 0x00 byte.
> On 23/11/14 23:19, Gareth France wrote:> The time and date is whenever
> the test was performed. I should imagine
>> there will be a lot of 'flags' Earth bond 25A yes, earth bond 10A
>> no, earth bond 100ma no, insulation test yes, visual pass, etc,
>> etc.
> And binary flags may well be encoded into a bit field, i.e. one or
> more bytes where each bit represents a yes or a no.
> I'm assuming the files you're currently working with are for your
> customers, and so can't reasonably be made public. Do you have access
> to some test files that could be shared? Many eyes on the problem may
> aid quicker progress. Also, the make and model of the device might help.
> JT
> - --
> - ---------------------------------------+--------------------------------
> James Tait, BSc                        |    xmpp:jayteeuk at wyrddreams.org
> Programmer and Free Software advocate  |        Tel: +44 (0)870 490 2407
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> Version: GnuPG v1
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