// stringstream example
//
// This program contains a function to determine the size of a file.
// If the file can’t be opened, the function throws a std::string
// that describes the problem.  It uses a stringstream to construct
// a useful error message, in accordance with Heckendorn’s Law.
//
// Can you spot the flaws in this program?
// The flaws are (ROT13):
// • Jul fubhyq /rgp/funqbj orvat vanpprffvoyr cerirag gur /rgp/ubfgf qngn?
// • reeab zvtug punatr orsber jr hfr vg

#include <cerrno>		// for errno
#include <cstring>		// for strerror
#include <fstream>		// for ifstream
#include <iostream>		// for cout, cerr
#include <sstream>		// for ostringstream

using namespace std;

// Return the size of the given file, or throw a std::string
// that explains why we couldn’t.
//
// Could more easily construct the error string just using +,
// but I’m using ostringstream for pedagogical purposes.

int size(const string &filename) {
    if (ifstream in{filename})
	return in.seekg(0,in.end).tellg();		// size of file
    else {
	// Couldn’t open the file.  Why?
	ostringstream oss;
	oss << "can’t open " << filename << ": " << strerror(errno);
	throw oss.str();
    }
}

int main() {
    try {
	// Why isn’t this just one giant cout expression?
	cout << "/bin/sync is "   << size("/bin/sync")   << " bytes.\n";
	cout << "/etc/shadow is " << size("/etc/shadow") << " bytes.\n";
	cout << "/etc/hosts is "  << size("/etc/hosts")  << " bytes.\n";
    }
    catch (const string &complaint) {
	cerr << complaint << '\n';
	return 1;
    }
    return 0;
}