Hi Pascal,
Pascal S. de Kloe wrote:
Hello Christopher,
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
scenario.
While such a change might be desirable, it would be an incompatible change, as
ZipInputStream.available() has been defined to return 0 or 1 since it was
first introduced in 1998 (ditto for base class
InflaterInputStream.available()). By now it is possible that some code is
depending on this behavior. Sad but true, and so we are loathe to change it.
Thanks,
Dave
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.
-Chris.
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.
