Re: hi all How to understand some codes in the function of __FD_SET?

[Dave Hylands <dhylands@xxxxxxxxx>]

Hi,

On Sat, Nov 2, 2013 at 11:35 PM, lx <lxlenovostar@xxxxxxxxx> wrote:

hi all:

       the codes of functions is:

 51 #undef  __FD_SET
 52 static __inline__ void __FD_SET(unsigned long __fd, __kernel_fd_set *__fdsetp)
 53 {
 54         unsigned long __tmp = __fd / __NFDBITS;
 55         unsigned long __rem = __fd % __NFDBITS;
 56         __fdsetp->fds_bits[__tmp] |= (1UL<<__rem);
 57 }

I can't understand the usage of __rem,How to understand it? thank you.

fds_bits is an array of entries which are each __NFDBITS long (in your example, each entry is 32-bits). __tmp gives you the index into the array. __rem is the remainder of the division, and gets  you the bit number within the 32-bit entry.

--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

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