线程题--拆分文件

Posted 2020-12-26 jiaan

将一个文件的前一半复制到一个文件，后一半复制到另一个文件，通过两个线程：

 1 #include<stdio.h>
 2 #include<semaphore.h>
 3 
 4 #include<pthread.h>
 5 
 6 FILE *fs,*fd1,*fd2;
 7 
 8 sem_t sem1,sem2; 定义信号变量
 9 
10 void *thread_handler1(void *arg)
11 {
12     char c;
13     int count=0;
14     sem_wait(&sem1);
15     printf("%d
",*((int *)arg));
16    //this from https://i.cnblogs.com/EditPosts.aspx?opt=1
　　　　 while((c = fgetc(fs)) > 0)
17     {
18         fputc(c,fd1);
19         if(++count >= *((int *)arg))判断是否复制到中间
20             break;
21     }
22     fclose(fd1);
23 
24     sem_post(&sem2);
25 }
26 
27 void *thread_handler2(void *arg)
28 {
29     char c;
30 //    fseek();
31     sem_wait(&sem2);
32     printf("enter
");
33     while((c = fgetc(fs)) > 0)
34     {
35         fputc(c,fd2);
36     }
37     fclose(fd2);
38 }
39 
40 int main(int argc, const char *argv[])
41 {
42     pthread_t thread1,thread2;定义线程变量
43 
44     fs = fopen("copy_half.c","r");
45     fd1 = fopen("text1.txt","w");打开文件
46     fd2 = fopen("text2.txt","w");
47     int middle,i;
48     fseek(fs,0,SEEK_END);
49     i = ftell(fs);
50     middle = i/2;
51     fseek(fs,0,SEEK_SET);
52 　　//from  https://i.cnblogs.com/EditPosts.aspx?opt=1
53     sem_init(&sem1,0,1);
54     sem_init(&sem2,0,0);
55     pthread_create(&thread1,NULL,thread_handler1,(void *)&middle);开第一个线程
56     pthread_create(&thread2,NULL,thread_handler2,(void *)&middle);开第二个线程
57 
58     pthread_join(thread1,NULL);等待线程结束
59     pthread_join(thread2,NULL);
60 
61     sem_destroy(&sem1);销毁信号量
62     sem_destroy(&sem2);
63     
64 
65 
66     return 0;
67 }