FS lab program for secondary indexing

#include <iostream>

#include <fstream>

#include <string>

#include <sstream>

using namespace std;

class secondary_index

{

  public:

      string Name_list[100];

      int Address_list[100];

      int count;

      void create_index();

      void insert();

      void remove(string);

      void delete_from_file(int);

      void search(string);

      int search_index(string);

      void read_from_file(int);

      string extract_Name(string);

      void sort_index();

     

};

void secondary_index::create_index()

{

      fstream file;

      int pos;

      string buffer,Name;

      count=-1;

      file.open("1.txt",ios::in);

      while (!file.eof())

      {

            pos=file.tellg();      

            buffer.erase();        

            getline(file,buffer);

            if (buffer.empty()) break; //imp since it reads the last \n and goes to new line

            Name=extract_Name(buffer);

            Name_list[++count]=Name;

            Address_list[count]=pos;     

      }

      file.close();    

      sort_index();          

}

string secondary_index::extract_Name(string buffer)

{

      string USN,Name;

      int i=0;

      USN.erase();     

      while (buffer[i]!='|')

        USN+=buffer[i++];

      Name.erase();

      i++;

      while (buffer[i]!='|')

        Name+=buffer[i++];

      return Name;

}

void secondary_index::sort_index()

{

      int i,j,temp_Address;

      string temp_Name;

      for (int i=0;i<=count;i++)

      {

        for (int j=i+1;j<=count;j++)

        {

            if (Name_list[i]>Name_list[j])

            {

              temp_Name=Name_list[i];

              Name_list[i]=Name_list[j];

              Name_list[j]=temp_Name;

              

              temp_Address=Address_list[i];

              Address_list[i]=Address_list[j];

              Address_list[j]=temp_Address;

      }}}

     

}

void secondary_index::insert()

{

      string USN, Name, Branch, sem, buffer;

      int Semester,pos;

      fstream file;    

      cout<<"\nUsn:";

      cin>>USN;

      cout<<"\nName:";

      cin>>Name;

      cout<<"\nBranch:";

      cin>>Branch;

      cout<<"\nSemster:";

      cin>>Semester;

      stringstream out;

      out << Semester;

      sem = out.str(); 

      buffer.erase();

      buffer=USN+'|'+Name+'|'+Branch+'|'+sem+'$'+'\n';

      file.open("1.txt",ios::out|ios::app);

      pos=file.tellp();

      file<<buffer;

      file.close();

      Name_list[++count]=Name;

      Address_list[count]=pos;

      sort_index();          

}

int secondary_index::search_index(string key)

{

      int low=0,high=count,mid=0,flag=0,pos;

      while (low<=high)

      {

            mid=(low+high)/2;

            if (Name_list[mid]==key) {flag=1; break;}

            if (Name_list[mid]>key) high=mid-1;

            if (Name_list[mid]<key) low=mid+1;

      }

      if (flag) return mid;

      else return 0;

}

void secondary_index::search(string key)

{

      int pos=0,t;

      string buffer;

     

      buffer.erase();  

      pos=search_index(key);

      if (pos){

            read_from_file(pos);

            t=pos;

            while (Name_list[++t]==key) read_from_file(t);

            t=pos;

            while (Name_list[--t]==key) read_from_file(t); 

            }

      else cout<<"\nNot Found";

}

void secondary_index::read_from_file(int pos)

{

      int address;     

      string buffer;

      fstream file;

      file.open("1.txt");

      address=Address_list[pos];

      file.seekp(address,ios::beg);

      getline(file,buffer);

      cout<<"\nFound the record:  "<<buffer;   

      file.close();

}

void secondary_index::remove(string key)

{

     

      int pos=0,t,choice;

      string buffer;

      buffer.erase();  

      pos=search_index(key);

      if (pos){

            read_from_file(pos);

            cout<<"\n Delete?";

            cin>>choice;

            if (choice) delete_from_file(pos);

            t=pos;

            while (Name_list[++t]==key){

                  read_from_file(t);

                  cout<<"\n Delete?";

                  cin>>choice;

                  if (choice) delete_from_file(t);

                  }

            t=pos;

            while (Name_list[--t]==key){

                  read_from_file(t);

                  cout<<"\n Delete?";

                  cin>>choice;

                  if (choice) delete_from_file(t);               

                  }

            }

      else cout<<"\n Not Found";

}

void secondary_index::delete_from_file(int pos)

{

      char del_ch='*';

      int i, address;

      fstream file;

      file.open("1.txt");

      address=Address_list[pos];

      file.seekp(address,ios::beg);

      file.put(del_ch);

      cout<<"\nRecord Deleted:  ";

     

      for (i=pos;i<count;i++)

            {

                  Name_list[i]=Name_list[i+1];

                  Address_list[i]=Address_list[i+1];

            }

      count--;

}

     

int main()

{

      int choice;

      string key;

      secondary_index i1;

     

      i1.create_index();

     

      while(1){

      cout <<"\nMain Menu\n------------\n1.Add  \n2.Search \n3.Delete \n4.EXIT\n---------------\nEnter the choice:";

      cin>>choice;     

      switch (choice)

      {

            case 1: cout<<"Data\n";

                  i1.insert();

                  break;

            case 2: cout <<"\n\nEnter the name";

                  cin>>key;

                  i1.search(key);

                  break;

            case 3:cout <<"\n\nEnter the name";

                  cin>>key;

                  i1.remove(key);

                  break;

            case 4: return 0;

            default:cout<<"\n\nWrong Choice";

                  break;

      }}

}