The original motivation is to further speed up launch time
for either non-selfie-based and selfie-based initialization
of the static network filtering engine (SNFE).
As a result of the refactoring:
Filters are no longer instance-based, they are sequence-of-
integer-based. This eliminates the need to create instances
of filters at launch, and consequently eliminates all the
calls to class constructors, the resulting churning of memory,
and so forth.
All the properties defining filter instances are now as much
as possible 32-bit integer-based, and these are allocated in a
single module-scoped typed array -- this eliminates the need
to allocate memory for every filter being instantiated.
Not all filter properties can be represented as a 32-bit
integer, and in this case a filter class can allocate slots
into another module-scoped array of references.
As a result, this eliminates a lot of memory allocations when
the SNFE is populated with filters, and this makes the saving
and loading of selfie more straightforward, as the operation
is reduced to saving/loading two arrays, one of 32-bit
integers, and the other, much smaller, an array JSON-able
values.
All filter classes now only contain static methods, and all
of these methods are called with an index to the specific
filter data in the module-scoped array of 32-bit integers.
The filter sequences (used to avoid the use of JS arrays) are
also allocated in the single module-scoped array of 32-bit
integers -- they used to be stored in their own dedicated
array.
Additionally, some filters are now loaded more in a deferred
way, so as reduce uBO's time-to-readiness -- the outcome of
this still needs to be evaluated, time-to-readiness is
especially a concern in Firefox for Android or less powerful
computers.
