splitbydate.cc

#include <iostream>
#include <fstream>
#include <sstream>
#include <unordered_map>
#include <string>
#include <cstring>
#include <exception>
#include <memory>


struct InvalidLine : public std::exception
{
    virtual const char *what () const throw ()
    {
        return "Invalidly formatted line";
    }
};

std::string get_filename (const std::string &prefix,const std::string &line)
{
    std::ostringstream ss;

    if (line.size () < 10 || std::strncmp (line.c_str (), "201", 3) != 0 ||
        line[4] != '-' || line[7] != '-')
        throw InvalidLine ();

    ss << prefix
       << line.substr (0, 4)
       << line.substr (5, 2)
       << line.substr (8, 2);

    return ss.str ();
}

int main (int argc, char **argv)
{
    typedef std::shared_ptr<std::ofstream> outfile_t;
    typedef std::unordered_map<std::string, outfile_t> handle_t;
    handle_t handles;

    for (char **i = argv + 1; *i; ++i) {
        std::ifstream infile (*i);
        std::string line;
        std::string prefix = std::string (*i) + "-";

        outfile_t outfile;

        while (std::getline (infile, line)) {
            try {
                std::string outfilename = get_filename (prefix, line);
                handle_t::iterator iter = handles.find (outfilename);

                if (iter == handles.end ()) {
                    outfile = outfile_t (new std::ofstream (
                                             outfilename.c_str ()));
                    handles.insert (std::make_pair (outfilename, outfile));
                } else
                    outfile = iter->second;
            } catch (InvalidLine &e) {
            }

            if (!outfile)
                continue;

            *outfile << line << '\n';
        }
    }

    return 0;
}