[delphizip] Re: New spanning scheme - allows SFX
- From: "Roger Aelbrecht" <Roger.Aelbrecht@xxxxxxxxxx>
- To: <delphizip@xxxxxxxxxxxxx>
- Date: Wed, 8 Jan 2003 18:49:20 +0100
James Turner wrote:
> The format proposed below would be incompatible with standard methods
> to assemble zip archives. In a spanned disk set, I can see no
> advantage, to combining the zip reader code into the zip file. To me,
> this seems to be unnecessary work producing a format that would not
> be compatible with existing zip software.
>
> As far as I can remember, Winzip uses a separate zip reader program
> with sfx disk sets.
>
> -- James Turner
>
>>
>> From: "Russell Peters" <russellpeters@xxxxxxxxxxx>
>> Date: 2003/01/08 Wed AM 05:00:24 GMT
>> To: <delphizip@xxxxxxxxxxxxx>
>> Subject: [delphizip] New spanning scheme - allows SFX
>>
>>
>> Proposal for new ZipSpan that can SFX
>>
>> The main file is the Central Directory or SFX + Central Directory
>> ie
>> optional SFX code
>> Central Directory
>> End of Central
>>
>> must all fit on one disk (the last one)
>> the part files are a header followed by data
>> ie
>> header (consists of, at least, signature + sequence number)
>> Data
>>
>>
>> Central Directory too big to fit on one disk?
>> - no problems just compress it as special entry in main file
>> directory. ('###DIRECTORY.ZIP' ?)
>> This would be automatically expanded (and used).
>>
>> Problems -
>> If Directory must be compressed, it would need to follow all other
>> data (so need to load multiple disks to get Directory)
>> Biggest problem is - if main file won't entirely fit on last disk
>> (in space not used by last part of data) that space is waisted!
>> not compatible with anything else though the main file could be
>> listed with anything
>> (may only show '###DIRECTORY.ZIP' ?)
>> Cannot be done with ZipMaster as yet!
>>
>> Russell Peters
>> http://www.users.bigpond.com/russellpeters/delphizip.html
I agree with James.
The format I proposed to Markus uses two separate files
the SFX stub and a added filelist
with :
- number of files
- for each file : name+ size+ disknbr
for this the size is calculated + size of sfx is kept free on disk1
then normal spanning is used then sfx-stub with table added to disk1
This allows standard zip programs to handle the archive as a normal zip
file. The sfx code does not use the central directory but the file list and
the local headers to find the files on the disks, disks are called when
needed
and if nobody changes the list they are in a logical order.
Can send you the code if you want to compare.
Unfortunately we don't have a working project
Roger Aelbrecht
http://web.wanadoo.be/driehoeksw
Other related posts:
