#include<fcntl.h>
#include<stdio.h>
#include<stdlib.h>
#include<sys/stat.h>


int IsHoleBlock(char *buf,int len)
{
	int i;
	for(i=0;i<len;i++)
	if(buf[i]!=0)
		return 0;
	return 1;
}

int main(int argc,char *argv[])
{
int sourcefd,destfd;
ssize_t nread;
ssize_t nwrite;
char *buf;
size_t len = 1;
struct stat st;

if(argc!=3)
{
	printf("usage: ./a.out <source filename> <destfilename>\n");
	return -1;
}

//if(fstat(sourcefd,&st)<0)
//{
//	printf("stat error\n");
//	return -1;
//}
//else
//{
//	len = st.st_blksize;
//}

if((sourcefd=open(argv[1],O_RDONLY))<0)
{
	printf("can't open source file\n");
	return -1;
}

if((buf=(char *)malloc(len))==NULL)
{
	printf("malloc error\n");
	return -1;
}

//if((destfd=creat(argv[2],O_WRONLY))<0)
if((destfd=open(argv[2],O_RDWR|O_CREAT|O_TRUNC))<0)
{
	printf("ceate file error\n");
	return -1;
}

while((nread=read(sourcefd,buf,len))>0)
{
if(!IsHoleBlock(buf,len))
	if((nwrite=write(destfd,buf,nread))<0)
		{
		printf("write error\n");
		exit(-1);
		}
}

if(nread<0)
{
	printf("read error\n");
	exit(-1);
}

free(buf);
close(sourcefd);
close(destfd);
return 0;
}