Hi, ZipFile.getEntry does optimizations to check for directory entries by adding a '/' to the encoded byte array. JDK-8242959 improved on this optimization, but a question was raised Jason Zaugg on whether the optimization is always valid[1]. Turns out it isn't, but only for non-ASCII compatible charsets.
While JarFiles are always assumed to be UTF-8-encoded or compatible, ZipFiles allow arbitrary encoding. E.g., UTF-16 would encode '/' (2F) as either 2F 00 or 00 2F, which means the hash code would differ and a directory "foo/" potentially not be found when looking up "foo". Further complications arise when/if the directory name ends with a code point that might be encoded so that the final byte is 2F, e.g. \u012F. This patch only enables this low-level optimization when the charset encoding used is known to be ASCII compatible in the sense that 2F will be encoded as single-byte 2F. UTF-8 is compatible in this sense - and since this is the charset exclusively used by JarFile these changes have little to no effect on startup performance in the cases we've been looking at. Webrev: http://cr.openjdk.java.net/~redestad/8243254/open.00/ Bug: https://bugs.openjdk.java.net/browse/JDK-8243254 I've partially repurposed ZipFile/TestZipFile to test some such corner cases. Mainly expanded it to test ZipFiles created with various non- standard encodings, but also slimmed it down so that it can actually run quickly and reliably - as well as enabled it in regular testing. The updated test fails both before and after JDK-8242959, but passes with the proposed changes. Testing: tier1+2 Thanks! /Claes [1] https://twitter.com/retronym/status/1252134723431747584?s=20
