[rfc][icedtea-web] Resource/ResourceTracker clean up

[Andrew Azores]

Hi,

Prompted by Omair's recent patches to fix caching, I started looking 
into the cache package too. I was not too happy with what I found in 
Resource and ResourceTracker :( here's the summary of the changes made:

Resource:
- stop using ints as bit fields for status flags. Use enum with EnumSet 
instead. isSet, changeStatus, and getStatusString heavily refactored for 
this.
-- setStatusFlag, unsetStatusFlag, resetStatus, isInitialized, hasFlags 
added
- made status field private
- made several fields final, some others can't be made final (at least 
not without even more refactoring)
- "transferred" and "size" long fields made volatile so that accesses 
are atomic
!! hashCode override added, because equals was already overridden 
without it !!
-- AND, Resource was used as the key type in a ConcurrentHashMap in 
ResourceTracker. Wonderful.

ResourceTracker:
- "import static" rather than creating copies of the status values in 
this class too...
- Collection fields declared more generically (eg as just Collection) 
where possible, which was most places
-- "queue" renamed "requestedDownloads" and changed from ArrayList to 
HashSet - the methods that provide for selecting the next resource to 
download from the "queue" don't even care about the ordering in the 
queue anyway, really, so being a List is an unnecessary restriction. I 
don't think we would want to allow for duplicates either, so a Set makes 
more sense to me unless duplicate entries are actually desired
-- "resources" also now a HashSet instead of ArrayList, for similar 
reasoning - ordering didn't matter to begin with, and I don't see the 
point in allowing duplicates
- SO many instances of ugly bit-fiddling to check a Resource's status 
cleaned up
- #wait() takes a Collection rather than an array, allows for some 
cleanup in #waitForResources()
- #findBestUrl() formatting fixed, no actual changes made here
- #selectByFlag() renamed to #selectByStatus(), extracted most logic 
into #selectByFilter() (required since there is no more explicit 
UNINITIALIZED status flag)

There's still a lot of fixing that can be done in ResourceTracker 
however. eg using a proper ThreadPool, proper synchronization rather 
than the global "lock" object and locking on a few other important 
fields. I'll start looking into that after this goes in.

Thanks,

-- 
Andrew A

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