Advanced Programming in the UNIX® Environment

ptg10805159

666 Advanced IPC Chapter 17

argument toselect.Wealso keep track of the highest index in use in the

clientarray.)

2. An existing client’s connection can be ready for reading. This means that the
   client has either terminated or sent a new request. Wefind out about a client
   termination byreadreturning 0 (end of file). Ifreadreturns a value greater
   than 0, there is a new request to process, which we handle by calling
   handle_request.
   We keep track of which descriptors arecurrently in use in theallsetdescriptor
   set. As new clients connect to the server,the appropriate bit is turned on in this
   descriptor set. The appropriate bit is turned offwhen the client terminates.
   We always know when a client terminates, whether the termination is voluntary or
   not, since all the client’s descriptors (including the connection to the server) are
   automatically closed by the kernel. This differs from the XSI IPC mechanisms.
   Theloopfunction that usespollis shown in Figure17.30.
   #include "opend.h"
   #include <poll.h>

#define NALLOC 10 /*#pollfd structs to alloc/realloc */

static struct pollfd *

grow_pollfd(struct pollfd *pfd, int *maxfd)

{

int i;

int oldmax=*maxfd;

int newmax=oldmax + NALLOC;

if ((pfd = realloc(pfd, newmax * sizeof(struct pollfd))) == NULL)

err_sys("realloc error");

for (i = oldmax; i < newmax; i++) {

pfd[i].fd = -1;

pfd[i].events = POLLIN;

pfd[i].revents = 0;

}

*maxfd = newmax;

return(pfd);

}

void

loop(void)

{

int i, listenfd, clifd, nread;

char buf[MAXLINE];

uid_t uid;

struct pollfd *pollfd;

int numfd=1;

int maxfd=NALLOC;

if ((pollfd = malloc(NALLOC * sizeof(struct pollfd))) == NULL)

err_sys("malloc error");