Code:
#include iostream
#include istream
#include ostream
#include fstream
#include cstdlib
#include string
// the rot13 function
std::string rot13(std::string s)
{
static std::string const lcalph = "abcdefghijklmnopqrstuvwxyz", ucalph =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
std::string result;
std::string::size_type pos;
result.reserve(s.length());
for (std::string::iterator it = s.begin(); it != s.end(); ++it)
{
if ((pos = lcalph.find(*it)) != std::string::npos)
result.push_back(lcalph[(pos + 13) % 26]);
else if ((pos = ucalph.find(*it)) != std::string::npos)
result.push_back(ucalph[(pos + 13) % 26]);
else
result.push_back(*it);
}
return result;
}
// function to output the rot13 of a file on std::cout
// returns false if an error occurred processing the file, true otherwise
// on entry, the argument is must be open for reading
int rot13_stream(std::istream& is)
{
std::string line;
while (std::getline(is, line))
{
if (!(std::cout << rot13(line) << "\n"))
return false;
}
return is.eof();
}
// the main program
int main(int argc, char* argv[])
{
if (argc == 1) // no arguments given
return rot13_stream(std::cin) ? EXIT_SUCCESS : EXIT_FAILURE;
std::ifstream file;
for (int i = 1; i < argc; ++i)
{
file.open(argv[i], std::ios::in);
if (!file)
{
std::cerr << argv[0] << ": could not open for reading: " << argv[i]
<< "\n";
return EXIT_FAILURE;
}
if (!rot13_stream(file))
{
if (file.eof())
// no error occurred for file, so the error must have been in output
std::cerr << argv[0] << ": error writing to stdout\n";
else
std::cerr << argv[0] << ": error reading from " << argv[i]
<< "\n";
return EXIT_FAILURE;
}
file.clear();
file.close();
if (!file)
std::cerr << argv[0] << ": warning: closing failed for " << argv[i]
<< "\n";
}
return EXIT_SUCCESS;
}
Output:
Dharmendra
Qunezraqen
Hingu
Uvath
Sanfoundry
Fnasbhaqel
------------------
(program exited with code: 0)
Press return to continue
More C++ Programs:
