unix-mmap（）

#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <stdlib.h>
#include <string.h>


#define COPYINCR (1024*1024*1024)


int main(int argc,char **argv){
int fdin,fdout;
void *src,*dst;
size_t copysz;
struct stat sbuf;
off_t fsz = 0;
if(argc != 3)
exit(1);
if((fdin = open(argv[1],O_RDONLY))<0)
perror("open[1]");
if((fdout = open(argv[2],O_RDWR|O_CREAT|O_TRUNC,0644))<0)
perror("OPEN[2]");
if(fstat(fdin,&sbuf)<0)
perror("fstat");
if(ftruncate(fdout,sbuf.st_size)<0)
perror("ftruncate");
while(fsz < sbuf.st_size){
if((sbuf.st_size - fsz) > COPYINCR)
copysz = COPYINCR;
else
copysz = sbuf.st_size - fsz;
if((src = mmap(0,copysz,PROT_READ,MAP_SHARED,fdin,fsz))== MAP_FAILED)
perror("mmap");
if((dst = mmap(0,copysz,PROT_READ|PROT_WRITE,MAP_SHARED,fdout,fsz)) == MAP_FAILED)
perror("mmap2");

memcpy(dst,src,copysz);
munmap(src,copysz);
munmap(dst,copysz);
fsz+=copysz;
}
return 0;
}