RFR [9] 8139706: JarFile.getBytes could use InputStream.readNBytes

[Claes Redestad]

On 2015-10-15 23:21, Chris Hegarty wrote:
>> On 15 Oct 2015, at 21:59, ecki at zusammenkunft.net wrote:
>>
>> Hello,
>>
>> This does change a bit the semantic of the length check. If the stream would return more bytes than the zipentry says the new version would ignore them, the  old version was consuming then and then fail the check. However I am not sure if this is relevant.
> Right, there are certainly some subtle differences resulting from
> the proposed change. When working on JDK-8138978 I thought
> about using readNBytes, but played it safe as IOUtils was growing
> the bye[] lazily too, so no real perf difference.  In fact, I think I seen
> a test failure with using readNBytes here. I’ll have to check.

Seeing no jtreg test failures in java/util/zip nor java/util/jar (apart 
from 2 ignored tests), but I can see a reason for the current 
implementation being conservative: Corrupt/malicious jar files might lie 
about the entry length and report very large values, which could bring a 
down with OOME.

I believe we could be both safe and faster than baseline by adding a 
reasonable limit for when to use readNBytes, e.g., 32k would deal with 
the majority of .class files.

/Claes