第六章 I/O复用:select和poll函数:
#include <sys/select.h>
#include <sys/time.h>
int select(int maxfdp1, fd_set * readset, fd_set * writeset,
fd_set * exceptset, const struct timeval * timeout);
if timeout == NULL:
wait forever
else if timeout->tv_sec == 0 && timeout->tv_usec == 0:
no wait
else:
wait to timeout
success return ready-des-count, time out return 0, error return -1
struct timeval {
long tv_sec;
long tv_usec;
};
FD_SETSIZE
#include <sys/select.h>
void FD_ZERO(fd_set * fdset);
void FD_CLR(int fd, fd_set * fdset);
void FD_SET(int fd, fd_set * fdset);
int FD_ISSET(int fd, fd_set * fdset);
#include <sys/socket.h>
int shutdown(int sockfd, int howto);
howto:
SHUT_RD(0), SHUT_WR(1), SHUT_RDWR(2)
success return 0, error return -1
#include <sys/select.h>
#include <signal.h>
#include <time.h>
int pselect(int maxfdp1, fd_set * readset, fd_set * writeset,
fd_set * exceptset, const struct timespec * timeout,
const sigset_t * sigmask);
when call pselect, signal-mask be atomic to set as sigmask,
when return, signal-mask will be set back to it was
success return ready-des-count, time out return 0, error return -1
struct timespec {
time_t tv_sec;
long tv_nsec;
};
#include <poll.h>
int poll(struct pollfd * fdarray, nfds_t nfds, int timeout);
timeout == INFTIM: wait forever
timeout == 0: no wait
timeout > 0: wait for timeout (ms)
success return ready-des-count, timeout return 0, error return -1
struct pollfd {
int fd; /* descriptor to check, or < 0 to ignore */
short events; /* events of interest on fd */
short revents; /* events that occurred on fd */
};
events:
POLLIN, POLLRDNORM, POLLRDBAND, POLLPRI /* read */
POLLOUT, POLLWRNORM, POLLWRBAND /* write */
revents:
POLLIN, POLLRDNORM, POLLRDBAND, POLLPRI /* read */
POLLOUT, POLLWRNORM, POLLWRBAND /* write */
POLLERR, POLLHUP, POLLNVAL /* except */
示例:
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/select.h>
#include "myio.h"
#define max(a, b) ((a) >= (b) ? (a) : (b))
void
str_cli(FILE * fp, int sockfd)
{
int n;
int maxfdp1;
fd_set rset;
char sendline[MAXLINE];
char recvline[MAXLINE];
FD_ZERO(&rset);
for ( ; ; ) {
FD_SET(fileno(fp), &rset);
FD_SET(sockfd, &rset);
maxfdp1 = max(fileno(fp), sockfd) + 1;
if (select(maxfdp1, &rset, NULL, NULL, NULL) == -1) {
printf("select error: %s\n", strerror(errno));
exit(1);
}
if (FD_ISSET(sockfd, &rset)) { /* socket is readable */
if ((n = readline(sockfd, recvline, MAXLINE)) < 0) {
printf("readline error: %s\n", strerror(errno));
exit(1);
}
else if (n == 0) {
printf("str_cli: server terminated prematurely\n");
exit(0);
}
if (fputs(recvline, stdout) == EOF) {
printf("fputs error: %s\n", strerror(errno));
exit(1);
}
}
if (FD_ISSET(fileno(fp), &rset)) { /* input is readable */
if (fgets(sendline, MAXLINE, fp) == NULL) {
return; /* all done */
}
n = strlen(sendline);
if (writen(sockfd, sendline, n) != n) {
printf("writen error: %s\n", strerror(errno));
exit(1);
}
}
}
}
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/socket.h>
#include "myio.h"
#define max(a, b) ((a) >= (b) ? (a) : (b))
void
str_cli(FILE * fp, int sockfd)
{
int n;
int maxfdp1;
int stdineof;
fd_set rset;
char buf[MAXLINE];
stdineof = 0;
FD_ZERO(&rset);
for ( ; ; ) {
FD_SET(sockfd, &rset);
if (stdineof == 0) {
FD_SET(fileno(fp), &rset);
maxfdp1 = max(fileno(fp), sockfd) + 1;
}
else {
maxfdp1 = sockfd + 1;
}
if (select(maxfdp1, &rset, NULL, NULL, NULL) == -1) {
printf("select error: %s\n", strerror(errno));
exit(1);
}
if (FD_ISSET(sockfd, &rset)) { /* socket is readable */
if ((n = read(sockfd, buf, MAXLINE)) < 0) {
printf("read error: %s\n", strerror(errno));
exit(1);
}
else if (n == 0) {
if (stdineof == 1) {
return; /* normal termination */
}
else {
printf("str_cli: server terminated prematurely\n");
}
}
if (write(fileno(stdout), buf, n) != n) {
printf("fputs error: %s\n", strerror(errno));
exit(1);
}
}
if (FD_ISSET(fileno(fp), &rset)) { /* input is readable */
if ((n = read(fileno(fp), buf, MAXLINE)) < 0) {
printf("fputs error: %s\n", strerror(errno));
exit(1);
}
else if (n == 0) {
stdineof = 1;
if (shutdown(sockfd, SHUT_WR) == -1) { /* send FIN */
printf("shutdown error: %s\n", strerror(errno));
exit(1);
}
FD_CLR(fileno(fp), &rset);
continue;
}
if (writen(sockfd, buf, n) != n) {
printf("writen error: %s\n", strerror(errno));
exit(1);
}
}
}
}
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/select.h>
#include "myio.h"
#define LISTENQ 1024
#define SERV_PORT 34567
int
main(int argc, char * argv[])
{
int i;
int count;
int maxfd;
int listenfd;
int connfd;
int sockfd;
int nready;
int client[FD_SETSIZE];
ssize_t n;
fd_set rset;
fd_set allset;
char buf[MAXLINE];
socklen_t clilen;
struct sockaddr_in cliaddr;
struct sockaddr_in servaddr;
if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
printf("socket error: %s\n", strerror(errno));
exit(1);
}
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);
if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
printf("bind error: %s\n", strerror(errno));
exit(1);
}
if ((listen(listenfd, LISTENQ)) == -1) {
printf("listen error: %s\n", strerror(errno));
exit(1);
}
maxfd = listenfd; /* initialize */
count = 0; /* in use count of client[] array */
FD_ZERO(&allset);
FD_SET(listenfd, &allset);
for ( ; ; ) {
rset = allset; /* structure assignment */
if ((nready = select(maxfd+1, &rset, NULL, NULL, NULL)) == -1) {
printf("select error: %s\n", strerror(errno));
exit(1);
}
if (FD_ISSET(listenfd, &rset)) { /* new client connection */
clilen = sizeof(cliaddr);
connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);
if (connfd < 0) {
printf("accept error: %s\n", strerror(errno));
exit(1);
}
if (count >= FD_SETSIZE) {
printf("too many clients\n");
exit(1);
}
client[count++] = connfd; /* save descriptor */
FD_SET(connfd, &allset); /* add new descriptor to set */
if (connfd > maxfd) {
maxfd = connfd; /* for select */
}
if (--nready <= 0) {
continue; /* no more readable descriptors */
}
}
for (i = 0; i < count; ++i) { /* check all clients for data */
sockfd = client[i];
if (FD_ISSET(sockfd, &rset)) {
if ((n = read(sockfd, buf, MAXLINE)) < 0) {
printf("read error: %s\n", strerror(errno));
exit(1);
}
else if (n == 0) { /* connection closed by client */
if (close(sockfd) == -1) {
printf("close error: %s\n", strerror(errno));
exit(1);
}
FD_CLR(sockfd, &allset);
if (--count > 0) {
client[i] = client[count];
}
--i;
}
else {
if (writen(sockfd, buf, n) != n) {
printf("writen error: %s\n", strerror(errno));
exit(1);
}
}
if (--nready <= 0) {
break; /* no more readable descriptors */
}
}
}
}
}
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/stropts.h>
#include <poll.h>
#include "myio.h"
#ifndef INFTIM
#define INFTIM (-1)
#endif
#ifndef OPEN_MAX
#define OPEN_MAX (1024)
#endif
#define LISTENQ 1024
#define SERV_PORT 34567
int
main(int argc, char * argv[])
{
int i;
int size;
int count;
int listenfd;
int connfd;
int sockfd;
int nready;
ssize_t n;
char buf[MAXLINE];
socklen_t clilen;
struct pollfd * client;
struct sockaddr_in cliaddr;
struct sockaddr_in servaddr;
#ifdef _SC_OPEN_MAX
size = sysconf(_SC_OPEN_MAX);
if (size <= 0)
#endif
size = OPEN_MAX;
client = (struct pollfd *)malloc(sizeof(struct pollfd) * size);
if (client == NULL) {
printf("malloc error: %s\n", strerror(errno));
exit(1);
}
if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
printf("socket error: %s\n", strerror(errno));
free(client);
exit(1);
}
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);
if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
printf("bind error: %s\n", strerror(errno));
free(client);
exit(1);
}
if ((listen(listenfd, LISTENQ)) == -1) {
printf("listen error: %s\n", strerror(errno));
free(client);
exit(1);
}
client[0].fd = listenfd;
client[0].events = POLLRDNORM;
client[0].revents = 0; /* not need */
count = 1; /* in use count of client[] array */
for ( ; ; ) {
if ((nready = poll(client, count, INFTIM)) == -1) {
printf("poll error: %s\n", strerror(errno));
free(client);
exit(1);
}
if (client[0].revents & POLLRDNORM) { /* new client connection */
clilen = sizeof(cliaddr);
connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);
if (connfd < 0) {
printf("accept error: %s\n", strerror(errno));
free(client);
exit(1);
}
if (count >= size) {
printf("too many clients\n");
free(client);
exit(1);
}
client[count].fd = connfd;
client[count].events = POLLRDNORM;
client[count].revents = 0; /* need this in next "for" */
++count;
if (--nready <= 0) {
continue; /* no more readable descriptors */
}
}
for (i = 1; i < count; ++i) { /* check all clients for data */
if (client[i].revents & (POLLRDNORM | POLLERR)) {
sockfd = client[i].fd;
if ((n = read(sockfd, buf, MAXLINE)) < 0) {
if (errno == ECONNRESET) {
/* connection reset by client */
if (close(sockfd) == -1) {
printf("close error: %s\n", strerror(errno));
free(client);
exit(1);
}
if (--count > 1) {
client[i] = client[count];
}
--i;
}
else {
printf("read error: %s\n", strerror(errno));
free(client);
exit(1);
}
}
else if (n == 0) {
/* connection closed by client */
if (close(sockfd) == -1) {
printf("close error: %s\n", strerror(errno));
free(client);
exit(1);
}
if (--count > 1) {
client[i] = client[count];
}
--i;
}
else {
if (writen(sockfd, buf, n) != n) {
printf("writen error: %s\n", strerror(errno));
free(client);
exit(1);
}
}
if (--nready <= 0) {
break; /* no more readable descriptors */
}
}
}
}
}
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