poll() | 多路复用 I/O - 曲径通幽论坛

#include <poll.h>
extern int poll (struct pollfd *__fds, nfds_t __nfds, int __timeout);

/* Data structure describing a polling request.  */
struct pollfd
{
   int fd;                   /* poll 的文件描述符.  */
   short int events;          /* fd 上感兴趣的事件(等待的事件).  */
   short int revents;       /* fd 上实际发生的事件.  */
};

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <termios.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <poll.h>

int main (int argc, char **argv)
{
      int sfd1, sfd2, sfd3;

      struct pollfd Events [3];
      int retval;
      char buff [256];
      int readcnt;

      sfd1 = open ("/dev/ttyS1", O_RDWR | O_NOCTTY);
      sfd2 = open ("/dev/ttyS2", O_RDWR | O_NOCTTY);
      sfd3 = open ("/dev/ttyS3", O_RDWR | O_NOCTTY);

      ...
      /*各个串行环境设定程序*/
      ...

      memset (Event, 0, sizeof(Events));

      Event[0].fd = sfd1;
      Event[0].events = POLLIN | POLLERR;    /*关心读取和出错事件*/

      Event[1].fd = sfd2;
      Event[1].events = POLLIN | POLLERR;    /*关心读取和出错事件*/

      Event[2].fd = sfd3;
      Event[2].events = POLLIN | POLLERR;    /*关心读取和出错事件*/

      while (1) {
               /*等待事件*/
               retval = poll ((struct pollfd *)&Events, 3, 5000);
               if (retval < 0) {
                     perror ("poll");
                     exit (EXIT_FAILURE);
               }
               if (retval == 0) {
                     prinntf ("no data in 5 seconds.\\n");
                     continue;
               }

               for (i = 0; i < 3; i++) {
                     /*检查错误*/
                     if (Events[i].revents & POLLERR) {
                              printf ("device error!\\n");
                              exit (EXIT_FAILURE);
                     }

                     /*检查是否存在传递的数据(可读)*/
                     if (Events[i].revents & POLLIN) {
                              readcnt = read (Events[i].fd, buff, 256);
                              write (Events[i].fd, buff, readcnt);
                     }
               }
      }

      close (sfd1);
      close (sfd2);
      colse (sfd3);
}

[beyes@localhost poll]$ cat errors2 |grep "errno = 11" | wc -l
2191

#include <stdarg.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>
#include <syslog.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>


#define BUFFER_SIZE     1000000
#define LINE_LEN        256

typedef enum {B_FALSE, B_TRUE} boolean_t;               /*定义布尔变量*/

static char buf [BUFFER_SIZE];
int daemon_proc = 0;

int set_fsflag (int fd, int new_flags)
{
        int flags;

        if ((flags = fcntl (fd, F_GETFL)) == -1)        /*得到 fd 上的状态*/
                return (-1);

        flags |= new_flags;                             /*对 fd 添加新的属性*/

        if ((flags = fcntl (fd, F_SETFL, flags)) == -1) /*设置新属性*/
                return (-1);

        return (0);
}

int clear_fsflag (int fd, int new_flags)
{
        int flags;

        if ((flags = fcntl (fd, F_SETFL, flags)) == -1)
                return (-1);

        return (0);
}

static void err_common (boolean_t flag, int level, const char *text, va_list args)
{
        int old_errno;
        int n;
        char buf [LINE_LEN];

        old_errno = errno;      /*获得错误号*/
#ifdef NEED_SNPRINTF
        n = vsprintf (buf, text, args);                 /*n 为写入到 buf 中的字节数,不包括'\\0'*/
#else
        n = vsnprintf (buf, sizeof (buf), text, args);
#endif
        if (flag)
                snprintf (buf + n, sizeof (buf) - n, ": %s", strerror (old_errno));     /*附加出错具体提示*/
        strcat (buf, "\\n");

        if (daemon_proc)
                syslog (level, buf);    /*产生日志消息*/
        else {
                fflush (stdout);
                fprintf (stderr, "%s", buf);
                fflush (stderr);
        }
}

void log_msg (const char *text, ...)
{
        va_list arg;
        va_start (arg, text);
        err_common (B_FALSE, LOG_INFO, text, arg);
        va_end (arg);
}

void err_msg (const char *text, ...)
{
        va_list arg;

        va_start (arg, text);
        err_common (B_TRUE, LOG_ERR, text, arg);
        va_end (arg);

        exit (1);
}

void err_set (const char *text, ...)
{
        va_list arg;

        va_start (arg, text);
        err_common (B_TRUE, LOG_INFO, text, arg);
        va_end (arg);
}

int main (void)
{
        ssize_t n;
        ssize_t res;
        char *ptr;
        int errs;
        struct pollfd fds;

        errs = 0;
        n = read (STDIN_FILENO, buf, BUFFER_SIZE);
        log_msg ("Read %d bytes", n);

        set_fsflag (STDOUT_FILENO, O_NONBLOCK);

        fds.fd = STDOUT_FILENO;
        fds.events = POLLOUT;
        fds.revents = 0;

        ptr = buf;
        while (n > 0) {
                if (poll (&fds, 1, -1) == -1)
                        err_msg ("Can't poll");

                while ((n > 0) && ((res = write (STDOUT_FILENO, ptr, n)) > 0)) {
                        if (errs > 0) {
                                err_set ("write failed %d times\\n", errs);
                                errs = 0;
                        }

                        log_msg ("Wrote %d bytes", res);
                        ptr += res;
                        n -= res;
                }
        }
        clear_fsflag (STDOUT_FILENO, O_NONBLOCK);

        return (0);
}

[beyes@localhost poll]$ ./poll.exe < zypper.log 2> errors

[beyes@localhost poll]$ cat errors
Read 1000000 bytes
Wrote 4059 bytes
Wrote 4061 bytes
Wrote 4061 bytes
Wrote 4062 bytes
Wrote 4064 bytes
Wrote 4071 bytes
... ...

[beyes@localhost poll]$ wc -l errors
247 errors