Yet another I/O modeling

[Neil <neil@qlsc.sdu.edu.cn>]

hi,all
select/poll I/O modeling is fast,easy to use,it returns the number of fd 
which are acitvity,but you should scan the fd array to find which fd is 
ready,it costs a lot of time on a heavy load server.

I proposal another I/O modeling,named eselect.
struct eselect_struct{
    unsigned long readbitmap[MAXBITMAPFD];//suppose the MAXBITMAPFD is 
MAX OPEN                                         //FD NUMBER PER PROCESS
    int ret;//-1 on error,non-negative return value is the number of     
            //acitvity fds
}
we can use __set_bit(),__clear_bit(),__find_first_bit()....functions to 
maintain the bitmap.
So,you shouldnt scan the fd array any more.