IO 1.5

#include<head.h>
typedef struct
{
	const char * src;               //原文件的地址
	const char * dest;           //目标文件的地址
	int start;                     //要拷贝的起始位置
	int len;                       //要拷贝的长度
}info_t;

int get_src_file_len(const char *srcfile,const char * destfile)
{
	int sfd,dfd;
	int len=0;
	if((sfd = open(srcfile,O_RDONLY))==-1)
	{
		perror("open srcfile error");
		return -1;
	}
	if((dfd = open(destfile,O_RDWR|O_CREAT|O_TRUNC,0664))==-1)
	{
		perror("open destfile error");
		return -1;
	}

	len = lseek(sfd,0,SEEK_END);       //求出原文件长度

	close(sfd);
	close(dfd);

	return len;
}

int copy_file(const char *srcfile,const char * destfile,int start,int len)
{
	int sfd,dfd;
	char buf[10] = {0};
	int ret=0,count=0;
	if((sfd = open(srcfile,O_RDONLY))==-1)
	{
		perror("open srcfile error");
		return -1;
	}
	if((dfd = open(destfile,O_RDWR))==-1)
	{
		perror("open destfile error");
		return -1;
	}

	lseek(sfd,start,SEEK_SET);
	lseek(dfd,start,SEEK_SET);

	while(1)
	{
		ret = read(sfd,buf,sizeof(buf));

		count+=ret;
		if(ret==0 || count>len) 
		{
			write(dfd,buf,ret-(count-len)); 
			break;
		}  
		write(dfd,buf,ret); 
	}
	close(sfd);
	close(dfd);
	return 0;
}

void *task(void *arg)
{
	info_t f = *(info_t *)arg;
    copy_file(f.src,f.dest,f.start,f.len);
    pthread_exit(NULL);	
}

int main(int argc, const char *argv[])
{
	pthread_t tid1, tid2;            //定义两个线程号
    int len;                   //获取文件的长度
    if(argc != 3){
        fprintf(stderr,"input error,try again\n");
        fprintf(stderr,"usage:./a.out srcfile destfile\n");
        exit(EXIT_FAILURE);
    }

    len = get_src_file_len(argv[1],argv[2]);                  //获取要拷贝文件的长度

    info_t f[2] = {
        {argv[1],argv[2],0,len/2},
        {argv[1],argv[2],len/2,(len-len/2)},
    };

    if (pthread_create(&tid1, NULL, task, (void *)&f[0]))
	{    
		perror("thread 1 create error");
		return -1;
	}
    if (pthread_create(&tid2, NULL, task, (void *)&f[1]))
	{
		perror("thread 2 create error");
		return -1;
	}
    pthread_join(tid1,NULL);
    pthread_join(tid2,NULL);

    return 0;
	return 0;
}