#include
#include
using namespace std;
int main(int argc, char *argv[])
{
if(argc!=2) {
cout << "usage: SWAP \n";
return 1;
}
// open file for input/output
fstream io(argv[1], ios::in | ios::out | ios::binary);
if(!io) {
cout << "Cannot open file.\n";
return 1;
}
char ch1, ch2;
long i;
for(i = 0 ;!io.eof(); i+=2) {
io.seekg(i, ios::beg);
if(!io.good())
return 1;
io.get(ch1);
if(io.eof())
continue;
io.get(ch2);
if(!io.good())
return 1;
if(io.eof())
continue;
io.seekg(i, ios::beg);
if(!io.good())
return 1;
io.put(ch2);
if(!io.good())
return 1;
io.put(ch1);
if(!io.good())
return 1;
}
io.close();
if(!io.good()) return 1;
return 0;
}