// StringParser

// A StringParser object is constructed from a string.  Successive calls
// to the getNextField member function extract the next field from the
// string, returning true if it got one and false if there was no next field.
// Fields are separated by blank, tab, carriage return, or newline, and
// may be surrounded by single quotes, which are stripped off in the
// extracted field.  Two consecutive single quotes in a quoted field are
// converted to one.
//
// Here's an example of what it does:
//     StringParser parser("  abc  'def ghi'  'Don''t cry'  ''  jk ");
//     string s;
//     assert(parser.getNextField(s)  &&  s == "abc");
//     assert(parser.getNextField(s)  &&  s == "def ghi");
//     assert(parser.getNextField(s)  &&  s == "Don't cry");
//     assert(parser.getNextField(s)  &&  s == "");
//     assert(parser.getNextField(s)  &&  s == "jk");
//     assert(!parser.getNextField(s));

#include <string>

class StringParser
{
  public:
    StringParser(std::string text = "")
    {
        setString(text);
    }

    void setString(std::string text)
    {
        m_text = text;
        m_start = 0;
    }

    bool getNextField(std::string& field);

  private:
    std::string m_text;
    size_t m_start;
};

bool StringParser::getNextField(std::string& fieldText)
{
    m_start = m_text.find_first_not_of(" \t\r\n", m_start);
    if (m_start == std::string::npos)
    {
        m_start = m_text.size();
        fieldText = "";
        return false;
    }
    if (m_text[m_start] != '\'')
    {
        size_t end = m_text.find_first_of(" \t\r\n", m_start+1);
        fieldText = m_text.substr(m_start, end-m_start);
        m_start = end;
        return true;
    }
    fieldText = "";
    for (;;)
    {
        m_start++;
        size_t end = m_text.find('\'', m_start);
        fieldText += m_text.substr(m_start, end-m_start);
        m_start = (end != std::string::npos ? end+1 : m_text.size());
        if (m_start == m_text.size()  ||  m_text[m_start] != '\'')
            break;
        fieldText += '\'';
    }
    return true;
}