stuck in infinite loop

[adam2016]

I'm not sure why an infinite loop occurs it should eventually terminate,personStart is equal to 447 I checked and confirmed this while the loop was running and it just kept printing it out infinitely

and the file pointer in.tellg() is at 7

I converted it to an int and 7 is less than 447 yes but the getline functions should move the file pointer eventually ending the loop but it doesn't appear to be doing this

the first index numbers get printed out fine than -1 keeps on getting printed out

  vector<Person> people;
   map<int,Index> index;
   stringstream ss;

   ifstream in;
   in.open("randomAccess.txt");



   while(!in.eof()){

       string size;
       getline(in,size,':');
       string personStartString;
       getline(in,personStartString,':');
       int personStart;
       ss << personStartString;
       ss >> personStart;
       ss.str(string()); // clear string stream
       ss.clear();
       cout << "file p" << in.tellg() << endl;
       while((int)(in.tellg()) < personStart){

          cout << in.tellg() <<  " : " << personStart << endl;


       }
   }

[adam2016]

any body have any idea?

this problem is driving me crazy

[Repeater]

    while((int)(in.tellg()) < personStart){

          cout << in.tellg() <<  " : " << personStart << endl;


       }

Why would this loop not run forever? in.tellg doesn't change inside the loop, so why would it ever end?

[adam2016]

very true good point Repeater but

I tried changing the file pointer inside the second and it still got stuck in an infinite loop

while(!in.eof()){

       string size;
       getline(in,size,':');
       string personStartString;
       getline(in,personStartString,':');
       int personStart;
       ss << personStartString;
       ss >> personStart;
       ss.str(string()); // clear string stream
       ss.clear();
       cout << "file p" << in.tellg() << endl;
       while((int)(in.tellg()) < personStart){

          cout << in.tellg() <<  " : " << personStart << endl;
          string indexNumber;
         getline(cin,indexNumber,':');

       }
   }

still gets stuck in an infinite loop even though in.tellg() is changing with every read

[adam2016]

I didn't think reading from a file randomly would be so much work,

first of all I don't know how the math worked I just counted how many spaces the index size was off by and subtracted it,if anybody can tell me where I went wrong calculating the index size that would be great

here is the code as said I didn't think it would get that complicated spent hours on this

note the commented out code is the code used to write to the file

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

using namespace std;

class Index{

  public:

  int locationID;
  int startByte;
  int size;

  Index(){ }
   Index(int s,int siz){

     startByte = s;
     size = siz;

   }

    Index(const Index& other){

       startByte = other.startByte;
       locationID = other.locationID;
       size = other.size;
    }

    Index& operator=(const Index& other){

       startByte = other.startByte;
       locationID = other.locationID;
       size = other.size;

       return *this;
    }
};

class Person{

  public:

      string name;
      int age;

    Person(){}

   Person(string n,int a){

     name = n;
     age = a;
   }

    Person(const Person& other){

        name = other.name;
        age = other.age;
    }
    Person& operator=(const Person& other){

        name = other.name;
        age = other.age;
        return *this;
    }
};

void loadPerson(ifstream &in,map<int,Index> &index,stringstream &ss){

    // load a person dynamically from a txt file using indexes

     cout << "enter index you want" << endl;
     int inde;
     cin >> inde;
     Index *ind;

     for(map<int,Index>::iterator it = index.begin(); it != index.end(); it++){

        if(it->second.locationID == inde){

            ind = new Index(it->second.startByte,it->second.size);
            cout << "start by " << ind->startByte << endl;
            in.seekg(ind->startByte);
            cout << "file pointer is at : " << in.tellg() << endl;;

            string name;
            getline(in,name,':');

            string age;
            getline(in,age,':');

            cout << "age : " << age << "name :" << name << endl;

            int ageNum;
            ss << age;
            ss >> ageNum;
            ss.str(string()); // clear string stream
            ss.clear();
        }
     }
}

void loadPople(ifstream &in,map<int,Index> &index,stringstream &ss,vector<Person> &people){


        for(map<int,Index>::iterator it = index.begin(); it != index.end(); it++){

            in.seekg(it->second.startByte);

            string name;
            getline(in,name,':');

            string age;
            getline(in,age,':');

            cout << "age : " << age << "name :" << name << endl;

            int ageNum;
            ss << age;
            ss >> ageNum;
            ss.str(string()); // clear string stream
            ss.clear();

            Person p(name,ageNum);

            people.push_back(p);
        }
}

int main()
{
   //ofstream out;
  // out.open("randomAccess.txt");
       vector<Person> people;
       map<int,Index> index;
       stringstream ss;

       ifstream in;
       in.open("randomAccess.txt");

       int hello = 6;
       string size;
       getline(in,size,':');
       if(in.fail()){
          cout << "fail" << endl;
       }
       string personStartString;
       getline(in,personStartString,':');
       if(in.fail()){
           cout << "fail" << endl;
       }
       int personStart = 0;

       ss << personStartString;
       ss >> personStart;

       cout << "person start : " << personStart<< endl;
       ss.str(string()); // clear string stream
       ss.clear();
       int i = 0;

       while(in.tellg() < personStart){

           string indexString;
           getline(in,indexString,':');
           int indexNumber;
           ss << indexString;
           ss >> indexNumber;
           cout << in.tellg() << endl;
           ss.str(string()); // clear string stream
           ss.clear();

           string startByteString;
           getline(in,startByteString,':');
           int startByteNumber;
           ss << startByteString;
           ss >> startByteNumber;
           cout << in.tellg() << endl;
           ss.str(string()); // clear string stream
           ss.clear();

           string sizeString;
           getline(in,sizeString,':');
           int sizeNumber;
           ss << sizeString;
           ss >> sizeNumber;
           cout << in.tellg() << endl;
           ss.str(string()); // clear string stream
           ss.clear();

           Index ind(startByteNumber,sizeNumber);
           ind.locationID = i;
           index[indexNumber] = ind;

           cout << "i: " << i << endl;
           i++;
       }

   for(map<int,Index>::iterator it = index.begin(); it != index.end(); it++){

       cout << "index number : " << it->second.locationID << endl;
       cout << "start byte : " << it->second.startByte << endl;
       cout <<  "size : " << it->second.size << endl;

   }

   loadPerson(in,index,ss);
   loadPople(in,index,ss,people);

   for(int i = 0; i < people.size(); i++){ // print vector of people loaded from file

       cout << "name : " << people[i].name << endl;
       cout << "age : " << people[i].age << endl;
   }
}

//   for(int i = 0; i < 50; i++){
//
//       Person temp("adam",i);
//       people.push_back(temp);
//   }
//    try{
//
//     int size = people.size();
//     out << size;
//     out << ":";
//
//     cout << out.tellp() << endl;
//
//     //int indexSize((9 * 1 * 3) + (41 * 2 * 3) + 16 + 150 - 5);
//     int indexSize = (10 * 1) + (40 * 2) + 50 + (3 * 50) + 50 +(3 * 50) + 50 + (50*1) + 50-199;
//
//     int personStart = (int)(out.tellp() + indexSize + 3);
//
//     out << personStart;
//     out << ":";
//
//     int indexStart = (int)out.tellp();
//
//     out << indexStart;
//     out << ":";
//
//     int startPointer = personStart;
//     out.seekp(personStart);
//
//     startPointer = (int) out.tellp();
//
//     for(int i = 0; i < people.size(); i++){
//
//        out << people[i].name;
//        out << ":";
//        out << people[i].age;
//        out << ":";
//        // +100
//
//        cout << "sp" << startPointer << endl;
//        cout << "tellp" << out.tellp() << endl;
//
//        Index ind(startPointer,(int)(out.tellp() - startPointer));
//        ind.locationID = i;
//        index[i] = ind;
//        startPointer = (int) (out.tellp());
//     }  // 50 + 234 = 284
//
//     out.seekp(indexStart);
//
//     for(map<int,Index>::iterator it = index.begin(); it != index.end(); it++ ){
//
//        int number = it->first;
//        out << number;
//        out << ":";
//        out << it->second.startByte;
//        out << ":";
//        out << it->second.size;
//        cout << it->second.size << endl;;
//        out << ":";
//        //150
//     }
//    }catch(int e){
//
//       cout << e << endl;
//    } 

[Repeater]

How do you know it's changing? Are you dumping the value of in.tellg() to console every time round the loop?

[adam2016]

hi Repeater not in the code I showed but yes I did try to print the value of in.tellg() in the nested while loop and it displayed correctly for a while print out numbers you would expect than it would constantly print -1 and -1 would get print infinitely

[Repeater]

So in fact it's NOT changing. It's -1 all the time.

Now we look up the documentation: http://en.cppreference.com/w/cpp/io/basic_istream/tellg

-1 indicates a failure. Something has gone wrong. Perhaps the end of the file has been reached. Perhaps there was an error reading from the file. Functions exist, such as fail() , that you can use to check what he problem is, but your code needs to handle failures and not just assume that everything always works.

[adam2016]

very nice spot Repeater thats exactly the problem =)

I was almost pulling my hair out wondering where the -1 was coming from

thanks