Multi-Index Insert Failure Return (Boost)

Question

I'm currently using Boost's multi-index to help keep track of how many times a packet passes through a system.

Each time a system touches the packet, its IP address is added to a string, separated by commas. I go through that string then, tokenize it and add each IP found to a multi-index. Since the IPs are set to be unique right now, it's impossible for the same IP to be added twice to the multi-index. What should happen then is the value associated with the IP address should be incremented, counting how many times the packet went through that same IP.

Anyways, my issue comes in here. When I use something like stl map, I will get back a response which lets me know a key could not be added due to a duplicate key already existing within the map. Does Boost's multi-index offer anything similar? I know that if I attempt to insert the same IP it will fail, but how can I tell it failed?

Here's a portion of my current code:

// Multi-index handling
using boost::multi_index_container;
using namespace boost::multi_index;

struct pathlog
{
    string         hop;
    int     passedthru;

    pathlog(std::string hop_,int passedthru_):hop(hop_),passedthru(passedthru_){}

    friend std::ostream& operator<<(std::ostream& os,const pathlog& e)
    {
        os<<e.hop<<" "<<e.passedthru<<std::endl;
        return os;
    }
};

// structs for data
struct hop{};
struct passedthru{};

// multi-index container setup
typedef multi_index_container<
pathlog,
indexed_by<
ordered_unique<
tag<hop>,  BOOST_MULTI_INDEX_MEMBER(pathlog,std::string,hop)>,
ordered_non_unique<
tag<passedthru>, BOOST_MULTI_INDEX_MEMBER(pathlog,int,passedthru)> >
> pathlog_set;


int disassemblepathlog(const string& str, pathlog_set& routecontainer, const string& delimiters = ","){
    // Tokenizer (heavily modified) from http://oopweb.com/CPP/Documents/CPPHOWTO/Volume/C++Programming-HOWTO-7.html

    // Skip delimiters at beginning.
    string::size_type lastPos = str.find_first_not_of(delimiters, 0);
    // Find first "non-delimiter".
    string::size_type pos     = str.find_first_of(delimiters, lastPos);

    while (string::npos != pos || string::npos != lastPos)
    {
        // Found a token, add it to the vector.
        routecontainer.insert(pathlog((str.substr(lastPos, pos - lastPos)),1)); // if this fails, I need to increment the counter!
        // Skip delimiters.  Note the "not_of"
        lastPos = str.find_first_not_of(delimiters, pos);
        // Find next "non-delimiter"
        pos = str.find_first_of(delimiters, lastPos);
    }
}

Answer 1

Your call to insert returns a std::pair< iterator, bool >. The bool will be true only if the insert succeeded.

See http://www.boost.org/doc/libs/1_43_0/libs/multi_index/doc/reference/ord_indices.html#modifiers