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I think it is fine to move the validation immediately following findEND() though I am not sure there is a big win overall.
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<div class="">I also would prefer to see the test based off of an actual ZIP(or at least have the current/modified version of the test). I would prefer to avoid having another place where we have duplicate code creating a CEN et al as it is another maintenance
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<div class="">One option is to look at, is to store a zip in a byte array and modify the cenlen offset(you would want to provide the steps that were used to create the zip/byte array, I can provide you a trivial example if interested) </div>
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<div class=""> Best,</div>
<div class="">Lance</div>
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<div class="">On Jan 28, 2023, at 11:10 AM, Eirik Bjørsnøs <<a href="mailto:eirbjo@gmail.com" class="">eirbjo@gmail.com</a>> wrote:</div>
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<div dir="ltr" class="">On Sat, Jan 28, 2023 at 4:47 PM Alan Bateman <<a href="mailto:Alan.Bateman@oracle.com" class="">Alan.Bateman@oracle.com</a>> wrote:<br class="">
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The intention of the test was exercise a multi-GB CEN. So I think it<br class="">
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would be great if it could be re-written as an automatic test but I <br class="">
think it should be a real ZIP file, make use of sparse files might help.<br class="">
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<div class="">Alan,</div>
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<div class="">Yes, this change does exploit some knowledge of the internals of ZipFile. Specifically it assumes that:</div>
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<div class="">1: ZipFile seeks to the end of the JAR where it parses the End of central directory header, then seeks backward to parse an optional Zip64 End of central directory record / locator. At this point the CEN size is known.</div>
<div class="">2: That a too-large CEN size (obtained from ZIP64 or the normal end-of-cen record) will be rejected early, before any attempt of reading the CEN or other contents of the ZIP.</div>
<div class="">3: That ZipFIle will treat a ZIP file starting with an End of Central directory (ZIP64 or not) as empty, short-circuiting any checking of invalid CEN sizes.</div>
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<div class="">Based on these assumptions, the test knows as a fact that any data up to and including the CEN is never read by ZipFile. It seems a bit wasteful to create multiple GBs of data which we know will never be read?</div>
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<div class="">If you still prefer the test to use ZIPs which are valid from top to bottom, I can take a stab at making that faster than the current test.</div>
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<div class="">WDYT?</div>
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<div class="">Eirik. </div>
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Lance Andersen | Principal Member of Technical Staff | +1.781.442.2037</div>
<div>Oracle Java Engineering <br class="">
1 Network Drive <br class="">
Burlington, MA 01803<br class="">
<a href="mailto:Lance.Andersen@oracle.com" class="">Lance.Andersen@oracle.com</a></div>
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