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

//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>
pthread_mutex_t fastmutex;
typedef struct {
	char src_path[50];
	char des_path[50];
	int start;
	int len;
}file_path;
void *fun(void *file){
	file_path *file1=(file_path *)file;
	int fd1=open(file1->src_path,O_RDONLY);
	int fd2=open(file1->des_path,O_WRONLY);
	//移动光标f
	lseek(fd1,file1->start,SEEK_SET);
	lseek(fd2,file1->start,SEEK_SET);
	int buff[256];
	int sum=0;
	int half=file1->len;
	while(1){
		int res=read(fd1,buff,sizeof(buff));
		sum+=res;
		if(res<=0||sum>half){
			write(fd2,buff,res-(sum-half));
			break;
		}
		write(fd2,buff,res);
	}
}
int main(int argc, const char *argv[])
{
	if(argc!=3){
	return -1;
	}
	pthread_mutex_init(&fastmutex,NULL);
	file_path file1,file2;
	strcpy(file1.src_path,argv[1]);
	strcpy(file1.des_path,argv[2]);
	int fd1=open(argv[1],O_RDONLY);
	int fd2=open(argv[2],O_WRONLY|O_CREAT|O_TRUNC,0664);
	//计算大小
	int len=lseek(fd1,0,SEEK_END);
	int half=len/2;
	//赋值1
	file1.start=0;
	file1.len=half;
	//赋值2
	file2=file1;
	file2.start=len-half;
	close(fd1);
	close(fd2);
	//创建线程
	pthread_t pid1,pid2;
	pthread_create(&pid1,NULL,fun,&file1);
	pthread_create(&pid2,NULL,fun,&file2);
	//回收线程
	pthread_join(pid1,NULL);
	pthread_join(pid2,NULL);

	
	return 0;
}