Command Parser

command.cpp

#include "command.h"

Command::Command(const String & command)
{
    ParseState state = Default;
    int len = command.length();
    for(int i=0; i<len; i++)
    {
        char ch = command[i];
        switch(state)
        {
        case Default:
            switch (ch)
            {
            case ' ':
                if (!_tokens.size())
                    dataFinish();
                break;
            case ',':
                dataFinish();
                break;
            case '\\':
                state = Escaped;
                break;
            case '\"':
                state = Text;
                break;
            default:
                dataAppend(ch);
                break;
            }
            break;
        case Escaped:
            dataAppend(ch);
            state = Default;
            break;
        case Text:
            switch (ch)
            {
            case '\\':
                state = TextEscaped;
                break;
            case '\"':
                dataFinish();
                state = Default;
                break;
            default:
                dataAppend(ch);
                break;
            }
            break;
        case TextEscaped:
            dataAppend(ch);
            state = Text;
            break;
        }
    }
    dataFinish();
}

const String Command::GetText()
{
    return _tokens.size() ? _tokens[0] : String();
}

const int Command::GetArgCount()
{
    return _tokens.size() ? _tokens.size() - 1 : 0;
}

const String Command::GetArg(int argnum)
{
    return (int)_tokens.size() < argnum + 1 ? String() : _tokens[argnum+1];
}

void Command::dataAppend(const char ch)
{
    _data += ch;
}

void Command::dataFinish()
{
    if(_data.length())
    {
        _tokens.push_back(_data);
        _data = "";
    }
}

command.h

#ifndef _COMMAND_H
#define _COMMAND_H

#include <string>
#include <vector>

typedef std::string String;

class Command
{
public:
    Command(const String & command);
    const String GetText();
    const String GetArg(const int argnum);
    const int GetArgCount();

private:
    String _data;
    std::vector<String> _tokens;

    enum ParseState
    {
        Default,
        Escaped,
        Text,
        TextEscaped
    };

    void dataFinish();
    void dataAppend(const char ch);
};

#endif // _COMMAND_H

main.cpp

#include <iostream>
#include "command.h"

using namespace std;

int main()
{
    string cmd;
    cout << ">";
    getline(cin, cmd);
    Command command(cmd);
    cout << "GetText: " << command.GetText() << endl;
    int argc=command.GetArgCount();
    if(argc)
    {
        cout << "GetArgCount: " << argc << endl;
        cout << "Args:" << endl;
        for(int i=0; i<argc; i++)
        {
            cout << i << ": " << command.GetArg(i) << endl;
        }
    }
    return 0;
}