On Fri, Sep 28, 2012 at 3:39 PM, Willy Tarreau <[email protected]> wrote:
> On Fri, Sep 28, 2012 at 03:32:37PM +0800, Robin Lee wrote: > > Hi, I just began reading the code of HAproxy. > > > > I am confused a bit with the operations about fd_evts. The comment says: > > > > /* Each 32-bit word contains 2-bit descriptors of the latest state for 16 > > FDs : > > * desc = (u32 >> (2*fd)) & 3 > > > > Should that actually be > > desc = (u32 >> FD2BIT(fd)) & 3 > > > > (2*fd) may be larger than 32. > > Yes but as you can see it's just a comment explaining the general principle > (and BTW you got it right). If you look at the code you can find > FD2BIT(fd). > > And for what it's worth, most archs automatically trim bit counts during > shifts, so even without the mask it will work, though I would definitely > not rely on this ! > > Regards, > Willy > Thank you!
