linux 下阻塞睡眠等待poll函数简单实现

/* int poll(struct pollfd *fds, nfds_t nfds, int timeout); */

/*
   struct pollfd {
   int   fd;         // file descriptor 
   short events;     // requested events 
   short revents;    // returned events
   };
 */
/*
   The  bits that may be set/returned in events and revents are defined in
   <poll.h>:
POLLIN: There is data to read.(数据可读)
POLLOUT:Writing now will not block.（数据可读）
 */

#include <string.h>
#include <stdio.h>
003 #include <sys/types.h>
004 #include <sys/stat.h>
005 #include <fcntl.h>
006 #include <errno.h>
007 #include <poll.h>
008
009 /* int poll(struct pollfd *fds, nfds_t nfds, int timeout); */
010
011 /*
012    struct pollfd {
013    int   fd;         // file descriptor
014    short events;     // requested events
015    short revents;    // returned events
016    };
017  */
018 /*
019    The  bits that may be set/returned in events and revents are defined in
020    <poll.h>:
021 POLLIN: There is data to read.(数据可读)
022 POLLOUT:Writing now will not block.（数据可读）
023  */
024
025 #define OPEN_FLAGS O_RDWR|O_CREAT
026 #define OPEN_MODE  00777
027
028 #define W_DATA "howaylee"
029
030 int main(int argc, char* argv[])
031 {
032     int ret = -1;
033     int fd1 = -1;
034     int fd2 = -1;
035
036     char r_buf[12] = {0};
037
038     struct pollfd fds[2] = {0};
039
040     //open fd1
041     fd1 = open(argv[1], OPEN_FLAGS, OPEN_MODE);
042     if (-1 == fd1)
043     {
044         perror("open fd1 failed: ");
045         return -1;
046     }
047     //write fd1
048     ret = write(fd1, W_DATA, sizeof(W_DATA));
049     if(-1 == ret)
050     {
051         perror("write fd1 failed: ");
052         goto _OUT;
053     }
054     //lseek fd1 head
055     ret = lseek(fd1, 0, SEEK_SET);
056     if(-1 == ret)
057     {
058         perror("lseek fd1 failed: ");
059         goto _OUT;
060     }
061
062     //open fd2
063     fd2 = open(argv[2], OPEN_FLAGS, OPEN_MODE);
064     if (-1 == fd2)
065     {
066         perror("open fd2 failed: ");
067         return -1;
068     }
069
070     /*阻塞，等待程序读写操作*/
071
072
073     while(1)
074     {
075         //初始化pollfd
076         fds[0].fd = fd1;
077         //可读
078         fds[0].events = POLLIN;
079
080         fds[1].fd = fd2;
081         //可写
082         fds[1].events = POLLOUT;
083
084         //poll
085         ret = poll(fds, sizeof(fds)/sizeof(fds[0]), -1);
086         if(-1 == ret)
087         {
088             perror("poll failed: ");
089             goto _OUT;
090         }
091
092         //read fd1
093         if(fds[0].revents & POLLIN )
094         {
095             //清空缓存
096             //memset(r_buf, 0, sizeof(r_buf));
097             ret = read(fd1, r_buf, sizeof(r_buf));
098             if(-1 == ret)
099             {
100                 perror("poll read failed: ");
101                 goto _OUT;
102             }
103             printf("read = %s\n", r_buf);
104         }
105
106         //write fd2
107         if(fds[1].revents & POLLOUT )
108         {
109             ret = write(fd2, r_buf, sizeof(r_buf));
110             if(-1 == ret)
111             {
112                 perror("poll write failed: ");
113                 goto _OUT;
114             }
115             printf("write = %s\n", r_buf);
116         }
117     }
118
119     //close fd1 fd2
120     close(fd1);
121     close(fd2);
122
123 _OUT:
124     return ret;
125 }