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https://issues.apache.org/jira/browse/LUCENE-3448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13112554#comment-13112554
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Uwe Schindler edited comment on LUCENE-3448 at 9/22/11 1:41 PM:
----------------------------------------------------------------
Patch.
was (Author: thetaphi):
Patch.
One thing I don't like with FixedBitSet (makes code ugly and slows down for
some special cases in prevSetBit):
The usage pattern for nextSetBit/prevSetBit is the following:
{code:java}
for(int i=bs.nextSetBit(0); i>=0; i=bs.nextSetBit(i+1)) {
// operate on index i here
}
{code}
The problem is that the i+1 at the end can be bs.length(), but the code in
nextSetBit does not allow this (same applies to prevSetBit(0)). The above usage
pattern is in every programming book, so it should really be supported. The
check has to be done in all cases (with the current impl in the calling code).
If the check is done inside xxxSetBit() it can also be optimized to be only
called seldom and not all the time, like in the ugly looking replacement, thats
currently needed:
{code:java}
for(int i=bs.nextSetBit(0); i>=0; i=(i<bs.length()-1) ? bs.nextSetBit(i+1) :
-1) {
// operate on index i here
}
{code}
We should change this and allow out-of bounds indexes for those two methods
(they already do some checks in that direction). Enforcing this with an assert
is unuseable on the client side.
The test code for FixedBitSet also uses this, horrible. Please support the
common usage pattern for BitSets.
> Add FixedBitSet.and(other/DISI), andNot(other/DISI)
> ---------------------------------------------------
>
> Key: LUCENE-3448
> URL: https://issues.apache.org/jira/browse/LUCENE-3448
> Project: Lucene - Java
> Issue Type: Sub-task
> Components: core/other
> Affects Versions: 3.4, 4.0
> Reporter: Uwe Schindler
> Assignee: Uwe Schindler
> Fix For: 3.5, 4.0
>
> Attachments: LUCENE-3448.patch
>
>
> For the parent issue, and() and andNot() on DISIs and other FixedBitSets are
> missing. This issue will add those methods.
> The DISI methods (also the already existing or(DISI)) method will check for
> OpenBitSetIterator and do an inplace operation using the bits as optimization.
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