f06.cpp

//LAB PROGRAM 6. Write a C++ program to implement index on   secondary key, the name, for a file of student objects. Implement add ( ), search ( ), delete ( ) using the secondary index.
//use common search for search and delete.

#include<iostream>
#include<string>
#include<fstream>
#include<stdlib.h>

using namespace std;

class student
{
	public:
		string usn, name, sem;
		void enter_data();		
		void pack();			
}s1;

struct sec_index
{
	string usn, name;
	int addr;
}i2[100], found[20];
int cnt, find_cnt;

fstream fp;
int indexnums[20];

void create_index();				
void sort_index();
void search();
void lin_srch(string);
void del();
void error(int);

int main()
{
	int choice;
	
	system("clear");
	fp.open("record6.txt", ios::out|ios::app);
	fp.close();
	create_index();	

	while(1)
	{
		cout<<"1. to Add Record\n2. to Search for a record\n3. to delete a record\n4. Exit\n\nEnter choice : ";
		cin>>choice;
		switch(choice)
		{
			case 1: 
				s1.enter_data();
				fp.open("record6.txt",ios::out|ios::app);
				if(!fp)
					error(1);
				s1.pack();
				fp.close();
				break;
			case 2:	
				search();
				break;
			case 3: 
				del();
				break;
			default: 
				exit(0);
		}
	}
}

void create_index()
{
	int pos, i;
	string seg, usnbuf, namebuf;
	cnt = -1;
	fp.open("record6.txt", ios::in);
	if(!fp)
		error(1);
	while(fp)
	{
		usnbuf.erase();
		namebuf.erase();
		pos = fp.tellg();
		getline(fp, usnbuf, '|');
		getline(fp, namebuf, '|');
		getline(fp,seg);
		if(usnbuf[0] == '*'||usnbuf.length()==0||namebuf.length()==0)
			continue;
		cnt++;
		i2[cnt].usn = usnbuf;
		i2[cnt].name = namebuf;
		i2[cnt].addr = pos;
	}
	fp.close();
	sort_index();	
}

void sort_index()
{
	struct sec_index temp;	
	for(int i=0; i<=cnt; i++)
	{	
		for(int j=i+1; j<=cnt; j++)
			if(i2[i].name>i2[j].name)
			{
                temp.usn = i2[i].usn;
		        temp.name = i2[i].name;
		        temp.addr = i2[i].addr;

		        i2[i].usn = i2[j].usn;
		        i2[i].name = i2[j].name;
        		i2[i].addr = i2[j].addr;

	        	i2[j].usn = temp.usn;
        		i2[j].name = temp.name;
	        	i2[j].addr = temp.addr;
	        }	
    }
}

void student::enter_data()
{
	cout<<"\nEnter usn: ";
	cin>>usn;
	cout<<"\nEnter name: ";
	cin>>name;
	cout<<"\nEnter sem: ";
	cin>>sem;
}

void student::pack()
{
	int pos = fp.tellp();
	string buf = usn + "|" + name + "|" + sem + "|";	
	fp<<buf<<endl;
	cnt++;
	i2[cnt].addr =pos;
	i2[cnt].usn = usn;
	i2[cnt].name = name;
	sort_index();
}

void lin_srch(string name_srch)
{
	find_cnt = 0;int j=0;

	for(int i = 0; i<=cnt; i++)
	{
		if(i2[i].name == name_srch)
		{
            indexnums[j++]=i;
			found[find_cnt].usn = i2[i].usn;
			found[find_cnt].name = i2[i].name;
			found[find_cnt].addr = i2[i].addr;
			find_cnt++;
		} 	
	}
}
void search()
{
	string name_srch, buf;
	int ch;
	cout<<"\nEnter the Name of The student to be searched : ";
	cin>>name_srch;
	lin_srch(name_srch);
	if(find_cnt == 0)
	{
		cout<<"\nRecord Not Found!\n";
		return;
	}
	if(find_cnt == 1)
	{
		cout<<"\n1 Record Found\n";
		ch = 0;
	}
	if(find_cnt>1)
	{
		cout<<"\nMultiple Records Found!\n";
		for(int i = 0; i< find_cnt; i++)
			cout<<i<<". Usn = "<<found[i].usn<<endl;
		cout<<"\nEnter choice: ";
		cin>>ch;if(ch>find_cnt){cout<<"Invalid Range\n\n";return;}
	}
	cout<<"\nUsn|Name|Sem"<<endl;
	fp.open("record6.txt",ios::in);
	if(!fp)
		error(1);
	fp.seekg(found[ch].addr, ios::beg);
	getline(fp,buf);
	fp.close();
	cout<<buf<<endl;
}

void del()
{
	string name_srch;
	int ch;
	cout<<"\nEnter the Name of The student to be deleted : ";
	cin>>name_srch;
	lin_srch(name_srch);
	if(find_cnt == 0)
	{
		cout<<"\nRecord Not Found!\n";
		return;
	}
	if(find_cnt == 1)
	{
		cout<<"\n1 Record Found\n";
		ch = 0;
	}
	if(find_cnt>1)
	{
		cout<<"\nMultiple Records Found!\n";
		for(int i = 0; i< find_cnt; i++)
			cout<<i<<". "<<found[i].usn<<endl;
		cout<<"\nEnter choice: \n";
		cin>>ch;if(ch>find_cnt){cout<<"Invalid Range\n\n";return;}
	}
	cout<<"\nRecord Deleted\n\n";
	fp.open("record6.txt",ios::out|ios::in);
	if(!fp)
		error(1);
	fp.seekp(found[ch].addr, ios::beg);
	fp.put('*');
	fp.close();
	for(int i=indexnums[ch]; i<cnt;i++)
    {
		i2[i].usn = i2[i+1].usn;
		i2[i].name = i2[i+1].name;
		i2[i].addr = i2[i+1].addr;
	}
	cnt--;	
}

void error(int error_type)
{
	switch(error_type)
	{
		case 1: cout<<"\nFATAL ERROR!: Unable to open the record File\n";
			exit(0);		
	}
}