使用两个线程完成两个文件的拷贝，分支线程1拷贝前一半，分支线程2拷贝后一半，主线程回收两个分支线程的资源

#include <myhead.h>

struct Buf
{
	const char *file1;
	const char *file2;
	int start;
	int size;
};

int get_len(const char *arr,const char *brr)
{
	int fd1 = -1,fd2 = -1;
	if( (fd1=open(arr,O_RDONLY))==-1 )
	{
		perror("open error\n");
		return -1;
	}
	if( (fd2=open(brr,O_WRONLY|O_CREAT|O_TRUNC,0644))==-1 )
	{
		perror("open error\n");
		return -1;
	}
	int len = lseek(fd1,0,SEEK_END);
	close(fd1);
	close(fd2);
	return len;
}

void copy_file(const char *arr,const char *brr,int start,int size)
{
	int fd1 = -1,fd2 = -1;
	if( (fd1=open(arr,O_RDONLY))==-1 )
	{
		perror("open error\n");
		return ;
	}
	if( (fd2=open(brr,O_WRONLY))==-1  )
	{
		perror("open error\n");
		return ;
	}
	lseek(fd1,start,SEEK_SET);
	lseek(fd2,start,SEEK_SET);
	char buf[128]="";
	int num = 0;
	while(1)
	{
		int res = read(fd1,buf,sizeof(buf));
		num+=res;
		if(res==0 || num>size)
		{
			write(fd2,buf,res-(num-size));
			break;
		}
		write(fd2,buf,res);
	}
	close(fd1);
	close(fd2);
}
void *task1(void*arg)
{
	copy_file(((struct Buf *)arg)->file1,((struct Buf *)arg)->file2,((struct Buf *)arg)->start,((struct Buf *)arg)->size);
}

void *task2(void*arg)
{
	copy_file(((struct Buf *)arg)->file1,((struct Buf *)arg)->file2,((struct Buf *)arg)->start,((struct Buf *)arg)->size);
}

int main(int argc,const char *argv[])
{
	if(argc!=3)
	{
		perror("error\n");
		return -1;
	}

	int len = get_len(argv[1],argv[2]);

	struct Buf buf1 = {argv[1],argv[2],0,len/2};
	struct Buf buf2 = {argv[1],argv[2],len/2,len-len/2};

 	pthread_t tid1 = -1,tid2 = -1;
 	if( pthread_create(&tid1,NULL,task1,&buf1)!=0 )
	{
		printf("pthread_create1 error\n");
		return -1;
	}	
	if( pthread_create(&tid2,NULL,task2,&buf2)!=0 )
	{
		printf("pthread_create2 error\n");
	}
	
	pthread_join(tid1,NULL);
	pthread_join(tid2,NULL);
    return 0;
}

思维导图