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#include <stdio.h>#include <stdlib.h>#include <pthread.h>#include <ctype.h>struct arg_set { char *fname; int count;};struct arg_set *mailbox = NULL;pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;//互斥锁pthread_cond_t flag = PTHREAD_COND_INITIALIZER;//条件变量void *count_words(void *);int main(int argc, char *argv[]){ pthread_t t1, t2; struct arg_set args1, args2; int reports_in = 0; int total_words = 0; if ( argc != 3 ){ printf("usage: %s file1 file2\n", argv[0]); exit(1); } args1.fname = argv[1]; args1.count = 0; pthread_create(&t1, NULL, count_words, (void *) &args1); args2.fname = argv[2]; args2.count = 0; pthread_create(&t2, NULL, count_words, (void *) &args2); pthread_mutex_lock(&lock);//拿到互斥锁，进入临界区 while( reports_in < 2 ){ printf("MAIN: waiting for flag to go up\n"); pthread_cond_wait(&flag, &lock); //令线程等待在条件变量上 printf("MAIN: Wow! flag was raised, I have the lock\n"); printf("%7d: %s\n", mailbox->count, mailbox->fname); total_words += mailbox->count; if ( mailbox == &args1) pthread_join(t1,NULL);//等待线程t1执行结束 if ( mailbox == &args2) pthread_join(t2,NULL);//等待线程t2执行结束 mailbox = NULL; pthread_cond_signal(&flag); //通知等待在条件变量上的线程 reports_in++; } pthread_mutex_unlock(&lock);//释放互斥锁 printf("%7d: total words\n", total_words);}void *count_words(void *a){ struct arg_set *args = a; FILE *fp; int c, prevc = '\0'; if ( (fp = fopen(args->fname, "r")) != NULL ){ while( ( c = getc(fp)) != EOF ){ if ( !isalnum(c) && isalnum(prevc) ) args->count++; prevc = c; } fclose(fp); } else perror(args->fname); printf("COUNT: waiting to get lock\n"); pthread_mutex_lock(&lock);//拿到互斥锁，进入临界区 printf("COUNT: have lock, storing data\n"); if ( mailbox != NULL ){ printf("COUNT: oops..mailbox not empty. wait for signal\n"); pthread_cond_wait(&flag,&lock); } mailbox = args; printf("COUNT: raising flag\n"); pthread_cond_signal(&flag); //通知等在条件变量上的线程 printf("COUNT: unlocking box\n"); pthread_mutex_unlock(&lock); return NULL;} |