Parser.cxx

#include <boost/iterator/iterator_facade.hpp>
#include <iostream>
#include <string>
#include <vector>
#include <unordered_map>

using namespace std;

class Parser {
private:
	vector<vector<string> > m_map;
	unordered_map<string,int> m_field_idx;

public:
	bool load(/*const string & filename , const config & cfg*/){
		//load m_field_idx
		//load m_map

		m_field_idx["A"]=0;
		m_field_idx["B"]=1;
		m_field_idx["C"]=2;

		vector<string> v1;
		v1.push_back("A");
		v1.push_back("B");
		v1.push_back("C");
		vector<string> v2;
		v2.push_back("1");
		v2.push_back("2");
		v2.push_back("3");
		vector<string> v3;
		v3.push_back("a");
		v3.push_back("b");
		v3.push_back("c");
		m_map.push_back(v1);
		m_map.push_back(v3);
		m_map.push_back(v2);
		m_map.push_back(v3);

		return true;
	}

	int getFieldIdx(const string & field_name){
		if(m_field_idx.find(field_name)==m_field_idx.end()){
			return -1;
		}

		return m_field_idx[field_name];
	}

	vector<vector<string> >::iterator begin(){
		return m_map.begin();
	}

	vector<vector<string> >::iterator end(){
		return m_map.end();
	}
};


class parser_iterator : public boost::iterator_facade <parser_iterator, vector<vector<string> >::iterator, boost::forward_traversal_tag> {
private:
	friend class boost::iterator_core_access;
	void increment() { ++m_it; }

	bool equal(const parser_iterator & other) const {
		return this->m_it == other.m_it;
	}

	vector<string> & dereference() const { return *m_it; }

	vector<vector<string> >::iterator m_it;
public:
	parser_iterator(){}
	/*explicit*/ parser_iterator(const vector<vector<string> >::iterator & it): m_it(it) {}

	bool operator!=(const vector<vector<string> >::iterator & it){
		return m_it!=it;
	}

	void print(){
		vector<string> v = *m_it;
		for(int i=0; i<v.size(); ++i){
			cout<<v[i]<<",";
		}
		cout<<endl;
	}

	bool get(const int field_idx, string & field_val){
		const vector<string> & v = *m_it;
		if(field_idx<0 || field_idx>= v.size()){
			return false;
		}

		field_val = v[field_idx];
		return true;
	}
};


int main(){
	Parser parser;
	parser.load(/*filename, cfg*/);
	for (parser_iterator it=parser.begin(); it!=parser.end(); it++){
		//it.print();
		string val;
		if(it.get(parser.getFieldIdx("A"), val)){
			cout<<val<<endl;
		} else {
			cout<<"unable to get val"<<endl;
		}
	}
}