C++ How do i check for delimiter in this text file - c++

Question

i am new to C++. I would like to know how do i create a function to check for delimiter.
such as the case below
AD,Andorra,AN,AD,AND,20.00,Andorra la Vella,Europe,Euro,EUR,67627.00
AE,United Arab Emirates,AE,AE,ARE,784.00,Abu Dhabi,Middle East,UAE Dirham,AED,2407460.00
AF,Afghanistan,AF,AF,AFG,4.00,Kabul,Asia,Afghani,AFA,26813057.00
If the delimiter become $ or # instead of comma , how do i create a function to check for it and say , wrong format of text file.
Thanks!
Below is my readData code
void readData ()
{
FILE * pFile;
NoOfRecordsRead = 0;
char buffer [Line_Char_Buffer_Size];
pFile = fopen (INPUT_FILE_NAME , "r");
if (pFile == NULL)
perror ("Error opening file 'Countries.txt' !");
else
{
while ( !feof (pFile) )
{
char* aLine = get_line (buffer, Line_Char_Buffer_Size, pFile);
if (aLine != NULL)
{
// printf ("%d] aLine => %s\n", NoOfRecordsRead, aLine);
globalCountryDataArray [NoOfRecordsRead++] = createCountryRecord (aLine);
}
}
fclose (pFile);
}
}

Answer 1

#include <string>
#include <fstream>
#include <algorithm>
bool detect_comma(std::string file_name)
{
// open C++ stream to file
std::ifstream file(file_name.c_str());
// file not opened, return false
if(!file.is_open()) return false;
// read a line from the file
std::string wtf;
std::istream &in= std::getline(file, wtf);
// unable to read the line, return false
if(!in) return false;
// try to find a comma, return true if comma is found within the string
return std::find(wtf.begin(), wtf.end(), ',')!= wtf.end();
}
#include <iostream>
#include <cstdlib>
int main()
{
if(!detect_comma("yourfile.dat"))
{
std::cerr<< "File is not comma delimited!\n";
return EXIT_FAILURE;
}
// file is OK, open it and start reading
}
Edit: Added comments & example code

Answer 2

You would need a reliable way to find a location that you always expect the delimiter to be. If the first field is always 2 characters wide, you can check to see if the 3rd character is a ,. Otherwise, you can scan backwards on the first line of text to see if the first non-currency related character is a ,.
Edit: Your readData routine is very C-centric, as has been pointed out in comments. You can simplify it considerably by using C++ features.
std::string aLine;
std::ifstream pfile(INPUT_FILE_NAME);
while (pfile) {
std::getline(pfile, aLine);
if (aLine.size()) {
globalCountryDataArray.push_back(createCountryRecord(aLine));
}
}

Answer 3

A good way to perform your check is using the Boost.Regex library. You only have to define your regular expression and perform a check if your input matches the expression.
Sample code:
#include <string>
#include <boost/regex.hpp>
using namespace std;
int main()
{
const string input("AD,Andorra,AN,AD,AND,20.00,Andorra la Vella,Europe,Euro,EUR,67627.00");
const boost::regex ex("(?:(?!,)(\\d+\\.\\d*)|(\\w|\\s)*)(,(?:(?!,)(\\d+\\.\\d*)|(\\w|\\s)*))*");
cout << boost::regex_match(input.c_str(), ex) << endl;
return 0;
}
By the way: I'm not a regex expert so validate the expression :-)