Like everyone puts his solution, here is mine using template, lambda and tuple.
It can convert any CSV with wanted columns to a C++ vector of tuple.
It works by defining each CSV line element type in a tuple.
You also need to define the std::string to type conversion Formatter lambda for each element (using std::atod for example).
Then you got a vector of this struct corresponding to your CSV data.
You can reuse this easily to match any CSV structure.
StringsHelpers.hpp
#include <string>
#include <fstream>
#include <vector>
#include <functional>
namespace StringHelpers
{
template<typename Tuple>
using Formatter = std::function<Tuple(const std::vector<std::string> &)>;
std::vector<std::string> split(const std::string &string, const std::string &delimiter);
template<typename Tuple>
std::vector<Tuple> readCsv(const std::string &path, const std::string &delimiter, Formatter<Tuple> formatter);
};
StringsHelpers.cpp
#include "StringHelpers.hpp"
namespace StringHelpers
{
/**
* Split a string with the given delimiter into several strings
*
* @param string - The string to extract the substrings from
* @param delimiter - The substrings delimiter
*
* @return The substrings
*/
std::vector<std::string> split(const std::string &string, const std::string &delimiter)
{
std::vector<std::string> result;
size_t last = 0,
next = 0;
while ((next = string.find(delimiter, last)) != std::string::npos) {
result.emplace_back(string.substr(last, next - last));
last = next + 1;
}
result.emplace_back(string.substr(last));
return result;
}
/**
* Read a CSV file and store its values into the given structure (Tuple with Formatter constructor)
*
* @tparam Tuple - The CSV line structure format
*
* @param path - The CSV file path
* @param delimiter - The CSV values delimiter
* @param formatter - The CSV values formatter that take a vector of strings in input and return a Tuple
*
* @return The CSV as vector of Tuple
*/
template<typename Tuple>
std::vector<Tuple> readCsv(const std::string &path, const std::string &delimiter, Formatter<Tuple> formatter)
{
std::ifstream file(path, std::ifstream::in);
std::string line;
std::vector<Tuple> result;
if (file.fail()) {
throw std::runtime_error("The file " + path + " could not be opened");
}
while (std::getline(file, line)) {
result.emplace_back(formatter(split(line, delimiter)));
}
file.close();
return result;
}
// Forward template declarations
template std::vector<std::tuple<double, double, double>> readCsv<std::tuple<double, double, double>>(const std::string &, const std::string &, Formatter<std::tuple<double, double, double>>);
} // End of StringHelpers namespace
main.cpp (some usage)
#include "StringHelpers.hpp"
/**
* Example of use with a CSV file which have (number,Red,Green,Blue) as line values. We do not want to use the 1st value
* of the line.
*/
int main(int argc, char **argv)
{
// Declare CSV line type, formatter and template type
typedef std::tuple<double, double, double> CSV_format;
typedef std::function<CSV_format(const std::vector<std::string> &)> formatterT;
enum RGB { Red = 1, Green, Blue };
const std::string COLOR_MAP_PATH = "/some/absolute/path";
// Load the color map
auto colorMap = StringHelpers::readCsv<CSV_format>(COLOR_MAP_PATH, ",", [](const std::vector<std::string> &values) {
return CSV_format {
// Here is the formatter lambda that convert each value from string to what you want
std::strtod(values[Red].c_str(), nullptr),
std::strtod(values[Green].c_str(), nullptr),
std::strtod(values[Blue].c_str(), nullptr)
};
});
// Use your colorMap as you wish...
}
