Patch to fix BufferedInputStream.skip and bug 4254082
Pascal S. de Kloe
pascal at quies.net
Thu Jul 12 14:39:33 UTC 2007
Thank you for this information. :)
Would you happen to know if somebody even tried to make a better
available() for ZipInputStream?
For instance, the manual of gzip(1) notes that the compressed data can
only be a 5B larger per 32KB block than the original in the worst case
The current BufferedInputStream is known not to work in various
situations and with various other streams. I'd say that the correctness
of operation is more important than performance problems. Besides,
buffering a ZIP stream is weird, isn't it? Is documenting this
limitation a option?
For the specific patch posted earlier that day skip() should be fine but
read() and read(byte, int, int) will be affected.
On Wednesday 11 July 2007 00:35:09 you wrote:
> Hi Pascal, Bill, et al,
> I was responsible for integrating the contributed fix for 6192696.
> The problem with it was that it relied on a 'good' implementation of
> the available method. By 'good' I mean that it actually returns the
> amount of data that can be read without blocking, and not simply 1.
> ZipInputStream.available simply returns 1 (if there is any data
> available) as it is difficult to determine the amount of available
> data when dynamically uncompressing a data stream.
> Now, using available to try and fill as much of BufferedInputStream's
> internal buffer without blocking may result in reading only 1 byte at
> a time from the underlying stream, creating a performance
> degradation. See 6409506 and 6411870.
> I'm not sure what exactly is being proposed here, but if available is
> going to be used to optimize the amount of data actually skipped, be
> aware of the limitation of ZipInputStream.available and other 'bad'
> available implementations.
> Pascal S. de Kloe wrote:
> > Hello Martin,
> >> 6192696: BufferedInputStream.read(byte, int, int) can block if
> >> the entire buffer can't be filled
> >> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6192696
> > The problem is fill(). It doesn't check available(). The patch on
> > this mailing list is supposed to fix that too.
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