RFR 8056084: Refactor Hashtable to allow implementations without rehashing support

[Mikael Gerdin]

Hi Bengt,

On 08/28/2014 12:51 PM, Bengt Rutisson wrote:
>
> Hi Mikael,
>
> Looks good.
>
> One very minor nit if you feel like it.
>
> hashtable.cpp
>   50   if (_free_list) {
>
> Would you mind changing to "if (_free_list != NULL) {" ? I know it is
> not your code, but you are changing code in that method and did take me
> some extra brain cycles to realize that _free_list was not a bool
> indicating whether we were using a free list or not.

That seems like a good suggestion. The HotSpot style also explicitly 
mentions that using pointers as booleans should be avoided.

New webrev at: 
http://cr.openjdk.java.net/~mgerdin/8048268/hashtable-refactor/webrev.1/

/Mikael

>
> Thanks,
> Bengt
>
>
> On 2014-08-26 17:26, Mikael Gerdin wrote:
>> Hi all,
>>
>> For JDK-8048268 I need to do some refactoring of the Hashtable class
>> template.
>>
>>  From the bug description:
>> In order to simplify usage of the Hashtable<T, F> class the code to
>> perform
>> rehashing of the SymbolTable and StringTable should be factored out to an
>> intermediate class common to those two tables.
>> Also factor out HashtableEntry freelist allocation to allow
>> implementors an
>> easier route for providing their own memory management.
>>
>> Introducing the new intermediary superclass requires some calls to
>> superclass
>> functions to be qualified using the "this->" syntax due to the C++
>> template
>> name lookup rules.
>>
>> a comment about hashtable.cpp RehashableHashtable::dump_table:
>>
>> -  int bucket_bytes = (int)num_buckets * sizeof(bucket(0));
>> +  int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
>>
>> I decided to change the sizeof to count the size of the hashtable
>> bucket class
>> instead of the HashtableEntry* returned by bucket(0), even though they
>> may be
>> of the same size currently.
>>
>> Note that the webrev url refers to another bug.
>> Webrev:
>> http://cr.openjdk.java.net/~mgerdin/8048268/hashtable-refactor/webrev/
>> Buglink: https://bugs.openjdk.java.net/browse/JDK-8056084
>>
>> Testing: JPRT.
>>
>