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SubjectRe: [PATCH v4 0/8] Introduce the for_each_set_clump macro
On Tue, May 15, 2018 at 6:22 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:

> For example, suppose you would like to iterate over a 16-bit integer 4
> bits at a time, skipping over 4-bit groups with no set bit, where XXXX
> represents the current 4-bit group:
>
> Example: 1011 1110 0000 1111
> First loop: 1011 1110 0000 XXXX
> Second loop: 1011 XXXX 0000 1111
> Third loop: XXXX 1110 0000 1111
>
> Each iteration of the loop returns the next 4-bit group that has at
> least one set bit.
>
> The for_each_set_clump macro has six parameters:
>
> * clump: set to current clump index for the iteration
> * index: set to current bitmap word index for the iteration
> * offset: bits offset of the found clump in the bitmap word
> * bits: bitmap to search within
> * size: bitmap size in number of clumps
> * clump_size: clump size in number of bits
>
> The clump_size argument can be an arbitrary number of bits and is not
> required to be a multiple of 2.

I must say I'm impressed. Very nice arithmetics going on there.

If I can get some ACK for the bitops patch I'd be happy to merge
it all through the GPIO tree. The users are pretty clear cut.

BTW: if I could, I would pull out Donald Knuth's "The Art of Computer
Programming vol 4A" chapter 7.1.3 "Bitwise Tricks and Techniques"
to see what he has to say about the subject, but I don't have
that book as it turns out.

Yours,
Linus Walleij

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