What does this c code trying to do

Question

What does the following c code trying to do. I am not sure what does it calculate the value of width to

(width+31)&~31

Thank you.

Answer 1

It is rounding up to the next multiple of 32. It only works because 32 is a power of 2.

The bit pattern for  31 is ...000000000011111
The bit pattern for ~31 is ...111111111100000

When you and ~31 with any positive integer, you get a multiple of 32 (five low order bits are all zeroes).

Answer 2

它将width向上舍入为32的倍数。

Answer 3

它重置（关闭）“宽度”的最后5位，这导致width％32 = 0，即32的宽度倍数。