//	      Simple Index Files
//		 Gaurang Sinha
//	    gaurang85@rediffmail.com
//   gaurang.cjb.net -or- gaurang85.tripod.com
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>

struct student{
	char name[20];
	int roll,age,marks;
	}db;

struct index{
	int roll,flag;
	long offset;
	}index,tempi;

void add(),del(),sort(),modify(),search(),disp();

FILE *fp;
FILE *ind;

int main()
{
int s;
if(!(fopen("data.dat","r")))
	fp=fopen("data.dat","w");
if(!(fopen("index.dat","r")))
	ind=fopen("index.dat","w");
fcloseall();
A:
clrscr();
printf(	"\n\t\tMENU"
	"\n\t1. Add Record"
	"\n\t2. Delete Record"
	"\n\t3. Modify Record"
	"\n\t4. Search Record"
	"\n\t5. Display Records"
	"\n\t6. Exit"
	"\n\t::> ");
scanf("%d",&s);
if(s==6)return 0;
switch(s)
{
case 1:
	add();
	goto A;
case 2:
	del();
	goto A;
case 3:
	modify();
	goto A;
case 4:
	search();
	goto A;
case 5:
	disp();
	goto A;
default:
	goto A;
}
}

void add()
{
long offset;
fp=fopen("data.dat","rb+");
if(!fp){printf("\nError Opening DataBase File !");getch();return;}
ind=fopen("index.dat","rb+");
if(!ind){printf("\nError Opening Index File !");getch();return;}
printf("\n\n\tEnter Following Data");
printf("\nName : ");
scanf("%s",db.name);
printf("\nRoll No : ");
scanf("%d",&db.roll);
printf("\nAge : ");
scanf("%d",&db.age);
printf("\nMarks : ");
scanf("%d",&db.marks);
fseek(fp,0,SEEK_END);	//Goto End Of File
offset=ftell(fp);	//Get The Offset Value
fwrite(&db,sizeof(db),1,fp);
fclose(fp);
index.roll=db.roll;
index.offset=offset;
index.flag=1;
fseek(ind,0,SEEK_END);	//Goto End Of Index File
fwrite(&index,sizeof(index),1,ind);
fclose(ind);
sort();
}

void sort()
{
int i,j,max=0;
ind=fopen("index.dat","rb+");
if(!ind){printf("\nError Opening Index File !");getch();return;}
while(fread(&index,sizeof(index),1,ind))
	max++;
rewind(ind);
for(i=0;i<max;i++)
{
	for(j=0;j<max-(i+1);j++)
	{
		fseek(ind,j*sizeof(index),SEEK_SET);
		fread(&index,sizeof(index),1,ind);
		fread(&tempi,sizeof(index),1,ind);
		if(index.flag==1&&tempi.flag==1)
		{
			if(index.roll>tempi.roll)
			{
				fseek(ind,j*sizeof(index),SEEK_SET);
				fwrite(&tempi,sizeof(index),1,ind);
				fseek(ind,(j+1)*sizeof(index),SEEK_SET);
				fwrite(&index,sizeof(index),1,ind);
			}
		}
	}
}
fclose(ind);
}

void modify()
{
int roll,flg;
printf("\nEnter Roll No : ");
scanf("%d",&roll);
fp=fopen("data.dat","rb+");
if(!fp){printf("\nError Opening DataBase File !");getch();return;}
ind=fopen("index.dat","rb+");
if(!ind){printf("\nError Opening Index File !");getch();return;}
while(fread(&index,sizeof(index),1,ind))
{
	if((index.roll==roll)&&(index.flag==1))
	{
		flg=1;break;
	}
}
if(flg)
{
	db.roll=roll;
	printf("\n\n\tReEnter Following Data for RollNo %d",roll);
	printf("\nName : ");
	scanf("%s",db.name);
	printf("\nAge : ");
	scanf("%d",&db.age);
	printf("\nMarks : ");
	scanf("%d",&db.marks);
	fseek(fp,index.offset,SEEK_SET);
	fwrite(&db,sizeof(db),1,fp);
}
else
	printf("\n\nNo Such Record Found !!!");
fcloseall();
}

void search()
{
int roll,flg=0;
printf("\nEnter Roll No : ");
scanf("%d",&roll);
fp=fopen("data.dat","rb+");
if(!fp){printf("\nError Opening DataBase File !");getch();return;}
ind=fopen("index.dat","rb+");
if(!ind){printf("\nError Opening Index File !");getch();return;}
while(fread(&index,sizeof(index),1,ind))
{
	if((index.roll==roll)&&(index.flag==1))
	{
		flg=1;break;
	}
}
if(flg)
{
	fseek(fp,index.offset,SEEK_SET);
	fread(&db,sizeof(db),1,fp);
	printf("\n\n\tRecord Found !!!");
	printf("\nName : %s",db.name);
	printf("\nRoll No : %d",db.roll);
	printf("\nAge : %d",db.age);
	printf("\nMarks : %d",db.marks);
	fcloseall();
}
else
	printf("\n\nNo Such Record Found !!!");
getch();
}

void del()
{
char c;
int roll,flg=0;
printf("\nEnter Roll No : ");
scanf("%d",&roll);
fp=fopen("data.dat","rb+");
if(!fp){printf("\nError Opening DataBase File !");getch();return;}
ind=fopen("index.dat","rb+");
if(!ind){printf("\nError Opening Index File !");getch();return;}
while(fread(&index,sizeof(index),1,ind))
{
	if((index.roll==roll)&&(index.flag==1))
	{
		flg=1;break;
	}
}
if(flg)
{
	fseek(fp,index.offset,SEEK_SET);
	fread(&db,sizeof(db),1,fp);
	printf("\nName : %s",db.name);
	printf("\nRoll No : %d",db.roll);
	printf("\nAge : %d",db.age);
	printf("\nMarks : %d",db.marks);
	printf("\n\nAre You Sure You Want To Delete This Record ? ");
	c=getche();
	if(c=='y'||c=='Y')
	{
		fseek(ind,-(long)sizeof(index),SEEK_CUR);
		index.flag=0;
		fwrite(&index,sizeof(index),1,ind);
		printf("\n\nRecord Successfully Deleted !!!");
	}
}
else
	printf("\n\nNo Such Record Found !!!");
getch();
}

void disp()
{
fp=fopen("data.dat","rb+");
if(!fp){printf("\nError Opening DataBase File !");getch();return;}
ind=fopen("index.dat","rb+");
if(!ind){printf("\nError Opening Index File !");getch();return;}
printf("\n\n\tRollNo\tName\t\tAge\tMarks");
while(fread(&index,sizeof(index),1,ind))
{
	fseek(fp,index.offset,SEEK_SET);
	fread(&db,sizeof(db),1,fp);
	if(index.flag==1)
		printf("\n\t  %d\t%s\t\t %d\t  %d",
			db.roll,db.name,db.age,db.marks);
}
fcloseall();
getch();
}