| Re: archived data [message #54333 is a reply to message #54325] |
Tue, 05 June 2007 10:15   |
Vince Hradil
Messages: 574
Registered: December 1999
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Senior Member |
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On Jun 5, 12:12 pm, hradilv <hrad...@yahoo.com> wrote:
> On Jun 3, 10:54 am, Wox <nom...@hotmail.com> wrote:
>
>> Hi All,
>
>> I face the following situation: I'd like to do some online data
>> processing (i.e. during measurements) using IDL. However the data is
>> directly zipped by the acquisition system. Is it possible to read and
>> search (like file_search) in a zip archive without spawning unzip and
>> extract everything? Windows explorer does it, so it must be
>> possible...
>
>> I remember a similar question beeing posted here, but I couldn't find
>> it.
>
>> Thanks
>
> I just threw this together. Your milage may vary:
>
> function byte_to_hex, bytes
>
> nbytes = n_elements(bytes)
>
> hstr = string(bytes, format="(z2.2)")
>
> vform = '(' + strtrim(nbytes,2) + 'A)'
> hval = string( reverse(hstr),format=vform )
> val = 0l
> reads, hval, val, format="(z)"
>
> return, val
> end
>
> function zipcontents, fname
>
> endsig = '504b0506'
>
> finfo = file_info(fname)
> fsize = finfo.size
> fdata = bytarr(fsize)
>
> openr, lun, fname, /get_lun
> readu, lun, fdata
> free_lun, lun
>
> fcode = '(' + strtrim(fsize,2) + 'z2.2)'
>
> sdata = string(fdata, format=fcode)
>
> fptr = strpos(sdata, endsig) / 2
>
> fptr += 8
> numentries = byte_to_hex( fdata[fptr:fptr+1] )
> fptr += 8
>
> cd_offset = byte_to_hex( fdata[fptr:fptr+3] )
> fptr = cd_offset
>
> contents = strarr(numentries)
>
> for i=0l, numentries-1 do begin
> fptr += 28
>
> fnamelen = byte_to_hex( fdata[fptr:fptr+1] )
> fptr += 2
>
> extrafieldlen = byte_to_hex( fdata[fptr:fptr+1] )
> fptr += 2
>
> fcommentlen = byte_to_hex( fdata[fptr:fptr+1] )
> fptr += 14
>
> contents[i] = string(fdata[fptr:fptr+fnamelen-1])
>
> fptr = fptr + fnamelen + extrafieldlen + fcommentlen
>
> endfor
>
> return, contents
> end
Sorry, I meant to include this link: http://www.pkware.com/documents/casestudies/APPNOTE.TXT
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