Re: Any zip or tgz that decompress to itself ?

Hans-Peter Diettrich wrote:
Olivier Girant wrote:

I don't agree with you. The zip header format is not compressed and is not random data at all. One can take advantage of the potentially compressible header to have a zip file with the same size. It implies that the "incompressible" part size is not too high. I think that the difficulty is not to file size, but make the file respects the zip format with header and file list...

Quite a new approach: add data to an already compressed file, to make it compress better? Not impossible, but also not very probable.

DoDi

I do not intend to add data to "compress better"... I imagine the zip archive content like this:
- header for compressed file1
- compressed file1
- central directory for file1
- digital signature

The header and the central directory are very redundant, you can see some run of 0 and several fields are the same. Moreover you can play with archive comment to add even more redundancy, so as to make the global archive size equal to the uncompressed file size.

I don't bother if the zip file (and the compressed file inside) is very big, several MB. I just want the filename inside to be .zip and the compressed file to be expanded to the same content as the zip archive.

Are the explanation clearer ?

Olivier
.

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