On Tue, May 15, 2018 at 6:22 PM, William Breathitt Gray <vilhelm.g...@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
