On Tue, 11 Feb 2020 at 21:12, Matteo Bruni matteo.mystral@gmail.com wrote:
On Tue, Feb 11, 2020 at 5:33 PM Henri Verbeet hverbeet@gmail.com wrote:
On Mon, 10 Feb 2020 at 23:06, Matteo Bruni mbruni@codeweavers.com wrote:
+static void wined3d_bitmask_set_bits(DWORD *bitmask, unsigned int offset, unsigned int count) +{
- const unsigned int word_bit_count = sizeof(*bitmask) * CHAR_BIT;
- const unsigned int shift = offset % word_bit_count;
- bitmask += offset / word_bit_count;
- *bitmask |= ~0u >> (word_bit_count - min(count, word_bit_count)) << shift;
- ++bitmask;
- count -= min(count, word_bit_count - shift);
- if (!count)
return;- if (count >= word_bit_count)
- {
memset(bitmask, 0xffu, count / CHAR_BIT);bitmask += count / word_bit_count;count = count % word_bit_count;if (!count)return;- }
- *bitmask |= (1u << count) - 1;
+}
Does this intentionally not handle 0 count? I also suspect this has some room for simplification.
I wrote this patch a long time ago and looked through it so many times that it's hard for me to see problems. That's where review helps I guess :) I think I intentionally don't handle 0 count, I guess I could add an assert() at least. WRT simplification, this was originally written when I was looking into a game that sets most (or all) the float constants in one go so it somewhat reflects that (e.g. I think I started from the memset() part and then tacked the rest around it afterwards). I'll try to simplify it but I might ask for more specific suggestions if I can't find anything substantial...
I was mostly thinking you could get rid of the min() bits at the start by doing something like the following:
mask = ~0u << shift; mask_size = word_bit_count - shift; last_mask = (1u << ((start + count) & (word_bit_count - 1))) - 1; if (mask_size < count) { *bitmap |= mask; ++bitmap; count -= mask_size; mask = ~0u; } ... if (count) *bitmap |= (mask & last_mask);
It probably ends up being a little longer, but seems more straightforward and happens to handle 0 count as well.