IStream autotokenizer

#include <string>
#include <vector>
#include <istream>
#include <cstdarg>
using namespace std;

// [...]

vector<string> tokenize (istream &in, bool cont, int num, ...)  {
  vector<string> tokens;

  if (!in.good () || num < 1) return tokens;

  string line;
  bool foundLine = false;

  // read lines until we find something tokenizable
  while (in.good ())  {
    line = "";
    while (line == "" && in.good ()) // skip blank lines
      getline (in, line, '\n');

    if (line == "") break;  // eof

    // comments are defined as lines where the first
    // non-whitespace character is #
    // we would also like to skip lines containing only whitespace
    int firstChar = 0; // index of first non-whitespace

    while (firstChar < line.size ())  {
      if (line[firstChar] == ' ')
        firstChar++;
      else break;
    }

    if (firstChar >= line.size ()) // line contains only whitespace
      continue;

    if (line[firstChar] == '#')    // comment
      continue;

    foundLine = true;
    break;
  }

  if (!foundLine)  // eof
    return tokens;

  // tokenizing to a vector of size 1 is easy
  if (num == 1)  {
    tokens.push_back (line);
    return tokens;
  }

  // tokenize!
  va_list delimList;
  va_start (delimList, num);
  char current;  // last-used delimiter saved for later
  int lastDelim = -1;  // index of last-used delimiter

  for (int x = 0; x < (num-1); x++)  {
    // cstdarg doesn't like casting to char, so we cast to int first
    current = va_arg (delimList, int);
    int nextDelim = line.find (current, lastDelim+1);
    string tok = line.substr (lastDelim+1, nextDelim-lastDelim-1);

    tokens.push_back (tok);

    lastDelim = nextDelim;

    // break if we didn't actually find the last delimiter
    if (lastDelim == string::npos) break;
  }

  va_end (delimList);

  // don't continue - we want exactly num tokens (or less)
  if (!cont)  {
    // add the final token, unless we've already run out of line
    if (lastDelim != string::npos)
      tokens.push_back (line.substr (lastDelim+1));
    return tokens;
  }

  // continue tokenizing using final delimiter until line is exhausted
  while (lastDelim != string::npos)  {
    int nextDelim = line.find (current, lastDelim+1);
    string tok = line.substr (lastDelim+1, nextDelim-lastDelim-1);

    if (tok != "") tokens.push_back (tok);

    lastDelim = nextDelim;
  }

  return tokens;
}