This makes zero-element hash tables, which are common, smaller, and also avoids
unnecessary malloc/free pairs.
I did some measurements during some basic browsing of a few sites. I found that
35% of all live tables were empty with a few tabs open. And cumulatively, for
the whole session, 45% of tables never had an element added to them.
I kept all the existing PL_DHashTableAdd() calls fallible, in order to be
conservative, except for the ones in nsAtomTable.cpp which already were
followed immediately by an abort on failure.
I kept all the existing PL_DHashTableAdd() calls fallible, in order to be
conservative, except for the ones in nsAtomTable.cpp which already were
followed immediately by an abort on failure.
Because they are now just equivalent to |new PLDHashTable()| +
PL_DHashTableInit() and PL_DHashTableFinish(t) + |delete t|, respectively.
They're only used in a handful of places and obscure things more than they
clarify -- I only recently worked out exactly how they different from Init()
and Finish().
Because it's no longer needed now that entry storage isn't allocated there.
(The other possible causes of failures are much less interesting and simply
crashing is a reasonable thing to do for them.)
This also makes PL_DNewHashTable() infallible.
This makes zero-element hash tables, which are common, smaller, and also avoids
unnecessary malloc/free pairs.
I did some measurements during some basic browsing of a few sites. I found that
35% of all live tables were empty with a few tabs open. And cumulatively, for
the whole session, 45% of tables never had an element added to them.
There is more to be done w.r.t. simplifying initialization, which will occur in
the next patch.
Currently the setting of PLDHashTable::ops is very haphazard.
- PLDHashTable has no constructor, so it's not auto-nulled, so lots of places
null it themselves.
- In the fallible PLDHashTable::Init() function, if the entry storage
allocation fails we'll be left with a table that has |ops| set -- indicating
it's been initialized -- but has null entry storage. I'm not certain this can
cause problems but it feels unsafe, and some (but not all) callers of Init()
null it on failure.
- PLDHashTable does not null |ops| in Finish(), so some (but not all) callers
do this themselves.
This patch makes things simpler.
- It adds a constructor that zeroes |ops|.
- It modifies Init() so that it only sets |ops| once success is ensured.
- It zeroes |ops| in Finish().
- Finally, it removes all the now-unnecessary |ops| nulling done by the users
of PLDHashTable.
