sdb.cpp

#include <iostream>
#include <fstream>
#include <map>
#include <vector>

using namespace std;

map<string, string> data;
vector<string> keys;
int counter = 0;

void init()
{
	ifstream reader;
	reader.open("data");
	if(reader.is_open())
	{
		while( !reader.eof() )
		{
			string key;
			string value;
			if(	reader >> key )
				keys.push_back(key);
			if( reader >> value )
				data[key] = value;
		}
		
		counter = keys.size(); 
		reader.close();
	}
	else
	{
		ofstream maker;
		maker.open("data");
		maker.close();
	}
}

void save()
{
	fstream writer;
	writer.open("data", ios::app | ios::out);
	for( int i = counter; i <  keys.size(); i++)
	{
		writer << keys[i] << " " << data[keys[i]] << endl;
	}
	writer.close();
}

void set(string key, string value)
{
	data[key] = value;
	if( count(keys.begin(), keys.end(), key) == 0 )
		keys.push_back(key);
	cout << "<" << key << "," << value <<">" " was added.\n";
}

string get(string key)
{
	if( data.count(key) > 0 )
	{
		return data[key];
	}
	else
		return "Key not found.";
}

void deline(string key)
{
	string line;
	
    ifstream in("data");
    
    ofstream out("temp");
    
    while( getline(in, line) )
    {
        if(line.compare(0,key.length(), key) != 0)
        {
            out << line << endl;
        }
    }
    in.close();
    out.close();    
    remove("data");
    rename("temp","data");
}

void del(string key)
{
	if( data.count(key) > 0 )
	{
		cout << "<" << key << "," << data[key] <<">" " was deleted.\n";
		data.erase(key);
		keys.erase(remove(keys.begin(), keys.end(), key), keys.end());
		deline(key);
	}
	else
		cout << "Key does not exist.\n";
}

int main()
{
	init();
	bool c = 1;
	while(c)
	{
		string command;
		cin >> command;
		if( command ==  "set")
		{
			string key;
			string value;
			cin >> key;
			cin >> value;
			set(key, value);
		}
		else if( command ==  "get")
		{
			string key;
			cin >> key;
			cout << get(key) << endl;
		}
		else if( command == "delete")
		{
			string key;
			cin >> key;
			del(key);
		}
		else if( command == "exit")
		{
			c = 0;
		}
		else
		{
			cout << "Usage:\n";
			cout << "\tset key value to add or edit an entry\n";
			cout << "\tget key to retrieve an entry\n";
			cout << "\tdelete key to delete an entry\n";
			cout << "\texit to quit the program\n";
		}
			
	}
	save();
	return 0;
}