New archive file format (was: [omgps] collect feature requests)
alex.shulgin at gmail.com
Thu Jul 2 11:16:48 CEST 2009
On Thu, Jul 2, 2009 at 10:15, Laszlo
KREKACS<laszlo.krekacs.list at gmail.com> wrote:
> On Thu, Jul 2, 2009 at 8:42 AM, Alexander Shulgin<alex.shulgin at gmail.com> wrote:
>> I fail to see how is this true for normal tar files (vs. data read
>> from pipe). Can you elaborate please?
> Yepp, of course;)
> Simplification of tar archive:
> [1. file header][1. file][2.file header][2. file][3. file header][3. file]
> So how you read the third file from the archive? You read the file until the
> [3. file header], your test is successfull (is it the right file?),
> and you read the
> file itself. You see? You have read the whole file, just accessing the
> last item inside.
Yes, but is lseek(2) banned on neo? This is what I was talking about
then mentioned normal files (i.e. not pipes). :)
>> Pardon my ignorance, but wouldn't zip -0 do the trick for your purpose? :)
> It will do more or less, however there are three main problems with it:
> 1. you can only obtain the whole file from the archive. So you cant
> read a part of the file. So if you packed lets say a 700MB file to zip,
> you run out of memory on neo.
> At least this is the case on standard python zipfile module.
> 2. There is no random access feature, at
> least not in standard python modules.
> 3. There are significant processor time wasted when accessing to a file
> (many computation required). Btw, it needs to benchmark on the neo, how
> worse is it.
OK, I see now. Thanks for explanation.
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