[COMPRESS-466] Opening of a very large zip file is extremely slow compared to java.util.zip.ZipFile

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.18
• Fix Version/s: 1.19
• Component/s: Archivers
• Labels: zip

Environment

Tested both on Linux and OSX 10.13.6.

• Assignee: Unassigned
• Reporter: Jakob Sultan Ericsson
• Created: 26/Sep/18 12:35
• Updated: 09/Aug/19 15:41
• Resolved: 08/Oct/18 06:01

Description

We have a quite large zip file 35 gb and try to open this with ZipFile. 

        try (ZipFile zf = new ZipFile(new File("35gb.zip"))) {
            System.out.println("File opened..." + (System.currentTimeMillis() - start));
        }

This code takes about 300 000 - 400 000 ms (5-6 minutes).
If I run this with JDK-builtin java.util.zip.ZipFile, same code takes 300 ms (less than a second).

I'm not totally sure what it is the problem but I did some debugging and basically all time is spent in

    private void resolveLocalFileHeaderData(final Map<ZipArchiveEntry, NameAndComment> entriesWithoutUTF8Flag)

Anything that can be done to improve this?