1213作业

思维导图

作业

多线程实现文件拷贝，线程1拷贝一半，线程2拷贝另一半，主线程回收子线程资源。

#include <myhead.h>
typedef struct
{
	const char *p1;
	const char *p2;
	int len;
}Fun;

int length(const char *p1,const char *p2)
{
	int fd1= open(p1,O_RDONLY);
	if(fd1==-1)
	{
		perror("open");
		return -1;
	}
	int len = lseek(fd1,0,SEEK_END);
	int fd2 = open(p2,O_WRONLY|O_CREAT|O_TRUNC,0664);
	if(fd2==-1)
	{
		perror("open");
		return -1;
	}
	close(fd1);
	close(fd2);
	return len;
}

int copy(const char *p1,const char *p2,int n,int half)
{
	int fd1= open(p1,O_RDONLY);
	if(fd1==-1)
	{
		perror("open");
		return -1;
	}
	int fd2 = open(p2,O_WRONLY);
	if(fd2==-1)
	{
		perror("open");
		return -1;
	}
	lseek(fd1,n,SEEK_SET);
	lseek(fd2,n,SEEK_SET);
	char buff[1024];
	int sum=0;
	while(1)
	{
		int res = read(fd1,buff,sizeof(buff));
		sum += res;
		if(sum>half || res==0)
		{
			write(fd2,buff,(res-(sum-half)));
			break;
		}
		write(fd2,buff,res);
	}
	close(fd1);
	close(fd2);
	return 0;
}

void *fun(void *a)//子线程
{
	Fun *b = (Fun *)a;
	int len = b->len;
	copy(b->p1,b->p2,len/2,len/2);
	return NULL;
}

int main(int argc, const char *argv[])
{
	if(argc!=3)
	{
		printf("外部参数错误\n");
		return -1;
	}
	int len = length(argv[1],argv[2]);//获取文件长度

	Fun *s = malloc(sizeof(Fun));
	s->p1 = argv[1];
	s->p2 = argv[2];
	s->len = len;

	pthread_t tid;
	if(pthread_create(&tid,NULL,fun,s)==-1)//主线程
	{
		perror("pthread_create");
		return -1;
	}
	copy(argv[1],argv[2],0,len/2);

	pthread_join(tid,NULL);//等待子线程执行
	free(s);
	s==NULL;
	return 0;
}

互斥锁实现一遍

#include <myhead.h>
pthread_mutex_t fastmutex;
int k = 0;
void *fun(void *a)
{
	pthread_mutex_lock(&fastmutex);
	for(int i=0;i<500000;i++)
	{
		k+=1;
	}
	pthread_mutex_unlock(&fastmutex);
}

int main(int argc, const char *argv[])
{
	pthread_mutex_init(&fastmutex,NULL);
	pthread_t tid;
	for(int i=0;i<10;i++)
	{
		if(pthread_create(&tid,NULL,fun,NULL)==-1)
		{
			perror("pthread_create");
			return -1;
		}
	}
	sleep(2);
	printf("预想结果5000000\n");
	printf("实际结果%d\n",k);
	return 0;
}