Binary structure delete error - c++

Question

This is the whole program. Right now,the delete function does not write to the temp file. I'll try to change str array to string and see if it helps.
The program is supposed to read write edit search and sort binary file with structures.
#include <cstdlib>
#include <stdlib.h>
#include <iostream>
#include <fstream>
#include<string>
#include<limits>
#include<iomanip>
#include<stdio.h>
#include <errno.h>
using namespace std;
const int SIZE=40;
char typedef str[SIZE];
char fname[]="c:/solident.dat";
char tname[]="c:/temp.dat";
struct Rec{int id;str lname,fname;};
//prototypes
void menu(string&);
void engine(string&,Rec&,fstream&,fstream&,int,char[],char[]);
void openFile(char[]);
void addRec(Rec&,char[]);
void delAll(char[]);
void listAll(Rec&,fstream &,char[]);
void appRec(Rec&,fstream &,char[]);
void delRec(Rec&,fstream &, fstream &,char[],char []);
void srcRec(Rec&,fstream& ,char[]);
void modRec(Rec &J,fstream &outfile, char fname[]);
void sort();
int main(int argc, char *argv[])
{
string choice;
Rec Student;
fstream infile;
fstream outfile;
do
{
menu(choice);
engine(choice,Student,infile,outfile,SIZE,fname,tname);
} while(choice[0]!='0');
system("PAUSE");
return EXIT_SUCCESS;
}
//function menu
void menu(string &choice)
{
cout<<"\n\n\n\t\t========================";
cout<<"\n\n\t\tMENU \n";
cout<<"\n\t\t========================\n\n";
cout<<"\t\t[1] Open/check file\n";
cout<<"\t\t[2] Add records\n";
cout<<"\t\t[3] Append records\n";
cout<<"\t\t[4] Search for a record\n";
cout<<"\t\t[5] Delete a record\n";
cout<<"\t\t[6] Delete all records\n";
cout<<"\t\t[7] Modify a record\n";
cout<<"\t\t[8] List all records\n";
cout<<"\t\t[9] Sort all records\n";
cout<<"\t\t[0] Exit\n";
cout<<"\n\t\t========================= \n";
cout<<"\t\tYour choice :";
getline(cin,choice);
while (choice[0] !='1' && choice[0] !='2' &&choice[0] !='3' &&choice[0] !='4' &&choice[0] !='5' &&choice[0] !='6' &&choice[0] !='7' &&choice[0] !='8' &&choice[0] !='9' &&choice[0] !='0' )
{
cout<<"\n\t\t"<<choice<<" is invalid!";
cout<<"\n\t\tEnter correct choice: ";
getline(cin,choice);
}
cout<<"\n\t\t========================= \n\n";
}
//function
void engine(string &choice,Rec &J,fstream &infile,fstream &outfile,int SIZE,char fname[],char tname[])
{
switch (choice[0]){
case '1':
{
cout<<"Executing number "<<choice<<":"<<"Open/check file\n"<<endl;
openFile(fname);
break;
}
case '2':
{
cout<<"Executing number "<<choice<<":"<<"Add records\n"<<endl;
addRec(J,fname);
break;
}
case '3':
{
cout<<"Executing number "<<choice<<":"<<"Append records\n"<<endl;
appRec(J,outfile,fname);
break;
}
case '4':
{
cout<<"Executing number "<<choice<<":"<<"Search for a record\n"<<endl;
srcRec(J,infile,fname);
break;
}
case '5':
{
cout<<"Executing number "<<choice<<":"<<"Delete a record\n"<<endl;
delRec(J,infile, outfile,fname,tname);
break;
}
case '6':
{
cout<<"Executing number "<<choice<<":"<<"Delete all records\n"<<endl;
delAll(fname);
break;
}
case '7':
{
cout<<"Executing number "<<choice<<":"<<"Modify a record\n"<<endl;
modRec(J,outfile,fname);
break;
}
case '8':
{
cout<<"Executing number "<<choice<<":"<<"List all records\n"<<endl;
listAll(J,infile,fname);
break;
}
case '9':
{
cout<<"Executing number "<<choice<<":"<<"Sort all records\n"<<endl;
sort();
break;
}
default:exit(0);
}
}
//function
void openFile(char fname[])
{
cout<<"\nOpening file"<<fname<<"..."<<endl;
//confirm if file exists and opens
fstream infile;
fstream outfile;
infile.open(fname,ios::in|ios::binary);
if (infile.is_open())
{
cout<<"File "<<fname<<" exists, and was opened succesfully.";
}
infile.close();
//if fail ask to create
if (infile.fail())
{
cout<<"File does not exist. Create? [Y]/[N]";
char ch;
cin>>ch;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
//if yes then create file
if(ch=='y'|| ch=='Y')
outfile.open(fname,ios::out| ios::binary);
//if not created display error
if (outfile.fail())
{
cout<<"Error: File not created";
}
//else confirm creation of file
cout<<"File "<<fname<<" has been created.\n\n";
outfile.close();
}
}
//function
void addRec(Rec&J,char fname[])
{
fstream outfile;
outfile.open(fname,ios::out|ios::binary|ios::app);
char another[10];
do
{
cout<<"Please enter ID number :";
cin>>J.id;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout<<"\nPlease enter first name: ";
cin.getline(J.fname,SIZE);
cout<<"\nPlease enter lastname: ";
cin.getline(J.lname,SIZE);
outfile.write((char*) &J, sizeof(J));
cout<<"Add another record:[Y]/[N] ";
cin.get(another[0]);
cin.ignore(numeric_limits<streamsize>::max(), '\n');
} while(another[0]=='y'||another[0]=='Y');
cout<<"exiting to main menu.."<<endl;
}
//function
void delAll(char fname[])
{
fstream outfile;
cout<<"\n------------------\n"<<endl;
cout<<"\nDelete all records"<<fname<<"..."<<endl;
cout<<"\nAre you sure you want to delete all records in "<<fname<<" [Y]/[Any key for exit]?"<<endl;
char ch;
cin>>ch;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
if(ch=='y'||ch=='Y')
{
outfile.open(fname,ios::out|ios::binary|ios::trunc);
outfile.close();
}
else {cout<<"\nExiting to main menu..."<<endl;}
}
//function
void listAll(Rec&J,fstream &infile,char fname[])
{
infile.clear();
infile.open(fname,ios::in|ios::binary);
infile.read((char*)&J,sizeof(J));
cout<<"|=======================================================|"<<endl;
cout<<"| # | ID | FIRST | LAST |"<<endl;
cout<<"|=======================================================|"<<endl;
int count=1;
while(!infile.eof())
{
cout<<"| "<<setw(6)<<left<<count<<left<<"| "<<setw(9)<<J.id<<"| ";
cout<<left<<setw(14)<<J.fname<<"| ";
cout<<left<<setw(19)<<J.lname<<"|"<<endl;
infile.read((char*)&J,sizeof(J));
count=count+1;
cout<<"|-------------------------------------------------------|"<<endl;
}
infile.close();
}
//function
void appRec(Rec &J,fstream &outfile, char fname[])
{
outfile.open(fname,ios::out|ios::binary|ios::app);
outfile.clear();
cout<<"Please enter ID number :";
cin>>J.id;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout<<"\nPlease enter first name: ";
cin.getline(J.fname,SIZE);
cout<<"\nPlease enter lastname: ";
cin.getline(J.lname,SIZE);
outfile.write((char*) &J, sizeof(J));
outfile.close();
}
//----------------------------------------------------
void delRec(Rec&s,fstream &infile, fstream &outfile,char fname[],char tname[])
{
int current, request=1;
infile.open("c:/solident.dat",ios::in|ios::out|ios::binary);
if (!infile.is_open())
cout << "infile not open\n";
outfile.open("c:/temp.dat",ios::out|ios::binary|ios::trunc);
if (!outfile.is_open())
cout << "outfile not open\n";
for (;;)
{
infile.read((char*)&s, sizeof s);
if (infile.eof())
break;
current = s.id;
if (current != request)
outfile.write((char*)&s, sizeof s);
}
infile.close();
outfile.close();
infile.open("c:/temp.dat)",ios::in|ios::binary);
outfile.open("c:/solident.dat)", ios::out|ios::binary|ios::trunc);
for (;;)
{
infile.read((char*)&s, sizeof (s));
if (infile.eof())
break;
outfile.write((char*)&s, sizeof (s));
}
infile.close();
outfile.close();
}
void srcRec(Rec&Job,fstream &infile,char fname[])
{
cout << "Allowing the user to open a specific record.\n";
infile.open(fname, ios::in | ios::binary) ;
if(infile.fail())
{
cout << "Could not access file.\n";
}
else
{
int position; //user's position
//gets user's position
cout << "Please the record you would like to read: ";
cin >> position;
//ignore luki
cin.ignore(numeric_limits<streamsize>::max(), '\n');
//find the specific record, read it, and display it
infile.seekp((position - 1)*sizeof(Job));
infile.read((char*) &Job, sizeof(Job));
cout<<"|===============================================|"<<endl;
cout<<"| ID | FIRST | LAST |"<<endl;
cout<<"|===============================================|"<<endl;
cout<<left<<"| "<<setw(9)<<Job.id<<"| ";
cout<<left<<setw(14)<<Job.fname<<"| ";
cout<<left<<setw(19)<<Job.lname<<"|"<<endl;
}
//clears and closes the file
infile.clear();
infile.close();
}
void modRec(Rec &J,fstream &outfile, char fname[])
{
int position, //user's position
cntr = 0; //marks the current record within the file
cout << "Modifying a record.\n";
//open the two files
outfile.open(fname, ios::out | ios::in | ios::binary);
//get the user's desired position
cout << "please enter the record you would like to modify: ";
cin >> position;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout << endl;
if(outfile.fail())
{
cout << "File could not be read.\n";
}
else
{
//find the desired record
outfile.seekp((position - 1)*(sizeof(J)));
//get the user's modification
cout<<"Please enter ID number :";
cin>>J.id;
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout<<"\nPlease enter first name: ";
cin.getline(J.fname,SIZE);
cout<<"\nPlease enter lastname: ";
cin.getline(J.lname,SIZE);
//write over the desired record
outfile.write((char*) &J, sizeof(J));
}
//closes the files
outfile.close();
}
void sort()
{
int StructureSize, Idx1, Idx2;
FILE * binaryFile;
binaryFile = fopen("c:/solident.dat","rb+");
Rec Index, IndexTemp;
StructureSize = sizeof(Index);
fseek(binaryFile, 0, SEEK_END);
int fileSize = ftell(binaryFile);
rewind(binaryFile);
for (Idx1 = 0; Idx1 < fileSize; Idx1 += StructureSize)
{
for (Idx2 = 0; Idx2 < fileSize - StructureSize; Idx2 += StructureSize)
{
fread(&Index, StructureSize, 1, binaryFile);
fread(&IndexTemp, StructureSize, 1, binaryFile);
if (Index.id > IndexTemp.id)
{
fseek(binaryFile, -(StructureSize * 2), SEEK_CUR);
fwrite(&IndexTemp, StructureSize, 1, binaryFile);
fwrite(&Index, StructureSize, 1, binaryFile);
fseek(binaryFile, -StructureSize, SEEK_CUR);
}
else
{
fseek(binaryFile, -StructureSize, SEEK_CUR);
}
}
rewind(binaryFile);
}
fclose(binaryFile);
}

Answer 1

I don't know, there seem to be a few issues with this code. Here's just one of them though
int request=1,current;
...
while (!infile.eof())
{
s.id=current;
if (current!=request)
At no point in this code do you give current a value, but you are still using the variable. This is an uninitialised variable which is one reason your code isn't working.
I wonder if you meant to write
current=s.id;
instead? That would make a little more sense.
Try reading the file with a loop like this
infile.open("c:/solident.dat",ios::in|ios::out|ios::binary);
if (!infile.is_open())
cout << "infile not open\n";
outfile.open("c:/temp.dat",ios::out|ios::binary|ios::trunc);
if (!outfile.is_open())
cout << "outfile not open\n";
for (;;)
{
infile.read((char*)&s, sizeof s);
if (infile.eof())
break;
current = s.id;
if (current != request)
outfile.write((char*)&s, sizeof s);
}
infile.close();
outfile.close();
I wouldn't use fail() if I were you. I think it's extremely unlikely you'll detect a genuine read or write failure with it. It's much more likely to be an end of file error, or a failure to open a file.

Answer 2

#john .Thanks!
The first part works, but trying
rename(tempname,destination) does not work:
(the dest file exists)
Although the file temp.dat now contains the records minus the one deleted , the output is not written to the solident.dat file(it remains unchanged)
//So I tried to read every rec from file and write every record to dest file:
infile.open("c:/temp.dat)",ios::in|ios::binary);
outfile.open("c:/solident.dat)", ios::out|ios::binary|ios::trunc);
infile.read((char*)&s, sizeof s);
for (;;)
{
if (infile.eof())
break;
infile.read((char *)&s, sizeof (s));
outfile.write((char*)&s, sizeof (s));
}
infile.close();
outfile.close();
My understanding was, that outfile and infile are pretty straightforward: fstream.open, close , clear and it should work (I thought). It seems though that I'm missing something essential, because the simple delete binary struct function in the program seems to be a hit and miss and I've been going around in circles for a few days: parts of it work, then I add a few lines of code and either a function fails or the whole program fails.I tend to blame it on the compiler or devc++ :) but I'm certain it has to be the code that is invalid!
Thanks for help!