std.allocator: false pointers

[Andrei Alexandrescu via Digitalmars-d]

On 5/2/14, 11:50 AM, Steven Schveighoffer wrote:
> On Fri, 02 May 2014 14:42:52 -0400, Andrei Alexandrescu
> <SeeWebsiteForEmail at erdani.org> wrote:
>
>> On 5/2/14, 11:07 AM, Steven Schveighoffer wrote:
>
>>> What is the problem with keeping the bits together?
>>
>> More implementation (I have a BitVector type but not a KBitsVector!k
>> type), and scanning can't be done with fast primitives. -- Andrei
>
> Given a bitvector type, a 2bitvector type can be implemented on top of it.

If speed is no issue, sure :o). My intuition is that the TwoBitVector 
would need certain primitives from BitVector to work well.

> If one bit is "free", and another is "garbage", you just have to look
> for any set bits for free blocks. Yes, you have to look through 2x as
> much memory, but only until you find a free block.

Hmm, so if "garbage" is 0, then to allocate we'd need to scan for a 
"hole" of contiguous zeros (cheap) instead of a checkered pattern 
(expensive). I'll think about it.


Andrei