SharpZipLib - progress through fileS during extract

this has to be really easy, and it certainly seems to be a very frequently asked question, but I can't for the life of me find a 'straightforward' answer.

I want to create a ProgressBar that shows a Zip file being extracted by SharpZipLib.

The FastZip and开发者_运维技巧 FastZipEvents classes give progress on individual files but not on position within the overall Zip. That is, if there Zip contains 200 files, what file is currently being extracted. I don't care about the progress through individual files (e.g. 20KB through 43KB in Foo.txt).

I think I could fudge a way of doing this by first creating a ZipFile and to access the Count property. And then... using ZipInputStream or FastZip to extract and keep progress count myself but I think that means the Zip is effectively unzipped twice (once entirely into memory) and I don't like that.

Any clean way of doing this?

Regarding your last sentence: "I think that means the Zip is effectively unzipped twice".

Reading the content table of a zip file doesn't cost a lot at all (and doesn't access the contained files. You probably noticed that when you looked at a zip file with a "password" and only needed to enter the password when you tried to extract a file. You can look at the entries/content table just fine).

So I see nothing wrong with the approach of first checking the index/content table, storing the entry count (maybe even with compressed/uncompressed size?) and using the stream based api later.

FYI: DotNetZip has ExtractProgress event for this sort of thing. Code:

using (ZipFile zip = ZipFile.Read(ExistingZipFile))
{
  zip.ExtractProgress = MyExtractProgress; 
  zip.ExtractAll(TargetDirectory);    
}

The extractprogress handler looks like this:

    private void MyExtractProgress(object sender, ExtractProgressEventArgs e)
    {
        switch (e.EventType)
        {
            case ZipProgressEventType.Extracting_BeforeExtractEntry:
            ....
            case ZipProgressEventType.Extracting_EntryBytesWritten:
            ...
            case ZipProgressEventType.Extracting_AfterExtractEntry:
            ....
        }
    }

You could use it to drive the familiar 2-progressbar UI, with one bar showing progress for the archive, and another bar showing progress for the individual file within the archive.