[delphizip] Re: Very slow to delete files from ZIP file
- From: Fevosoft Support <support@xxxxxxxxxxxx>
- To: delphizip@xxxxxxxxxxxxx
- Date: Wed, 17 Oct 2007 00:54:27 +0800
Thank you Roger! I got it now.
Lewis Tian
Roger Aelbrecht wrote:
> Lewis wrote:
>
>> Thank you James, here are the detail information
>>
>> 1) The zip file is 247MB and it contains 277 files
>> 2) Delete a single file takes about 20 seconds
>> 3) It's on the local drive
>>
>> Before delete the file I shutdown the antivirus software.
>>
>> Do you mean ZIPMaster also need to copying required files to a new zip
>> file? If so, I believe that's why it's so slow to delete a file.
>>
>> And, do you have any documents about why program can't simply delete a
>> file from a ZIP file like hard disk? I want to know more information
>> about it. Thanks!
>>
>> Lewis Tian
>>
>>
>
> The structure of a zip file is such that you cannot simply delete a file
> from it.
>
> Each file has a local directory structure and has an entry in the
> central directory structure.
> Both contain information about the offset of the beginning of the file
> from the start of the archive.
> All these offset needs to be recalculated and all local and central
> directories have to be re-written, that's why the whole file needs to be
> re-written.
> If course all these directory structures need to be read first from the
> original file.
>
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