BitArray/BitFields - Review

[Dmitry Olshansky]

On 29-Jul-12 13:18, Era Scarecrow wrote:
> On Sunday, 29 July 2012 at 09:03:08 UTC, Dmitry Olshansky wrote:
>> On 29-Jul-12 12:55, Era Scarecrow wrote:
>>> Doing it this way the arguments being passed as reference slices
>>> would ensure unneeded copies wouldn't be made. On the other hand a
>>> smaller portion of the code would need to be updated. Along with that
>>> a slice could be set as COW allowing quite a bit of flexibility.
>>>
>>>  Thoughts?
>>
>> Hm... and small array optimizations go where? BitArraySlice won't be a
>> full reference type if it does it.
>
>   I was thinking about that; If need be the slice can point to another
> slice which holds the actual small array (Kinda a long workaround). The
> way to small array optimization to work would be if BitArray generated
> it, since when you go to slicing you either reference the original data
> in the slice, or you could drop the small array optimization; although a
> loss it would simplify code until you come back to it once the code is
> working the way it should.
>
>   Another idea is to convert the struct into a class instead, which
> would allow some options, but won't be a perfect fit, and inheritance
> could be used; which would solve some of the small array optimization,
> but at what cost?

I have simpler suggestion. Maybe doing it as 2 containers:

BitSet is a plain value type with small array optimization (what you 
called BitArray in last 2 posts) and no slicing (only as opSlice() i.e. 
as a whole). Best used for small things under < 1000 bits (as even dup 
will be cheap enough).

BitArray is class or struct that has reference smenatics and drops small 
array optimization in favor of having simple & fast slicing
Best used for big arrays with no less then 100-200 bits.


-- 
Dmitry Olshansky