convert from C++ to C

[Unregistered]

Hi all. Really need on how to convert this code from C++ to C.
Its actually a program for an address book. Any help will be greatly appreciated

#include <fstream.h>
#include <cstring>
#include <cstdio>

class book {
//these are only visible by class book and its member functions
private:
int choice;
char *File;
char name[30];
char phone[13];
char email[30];
int srchtype;
char srchstr[30];

//these are visible to book objects
public:

//this constructor is called whenever an object of
//class book is created to initialize our variables
book() { File="addresses.dat"; choice = 0; };

//function prototypes
void ShowBook();
void AddEntry();
int Menu();
void Print();
void SearchMenu();
bool Found(book&);

//some helper functions
void Flush() { while (cin.get() != '\n') cin.get(); }
bool CheckOpen(fstream &f) {
if (!f.is_open()) {
cerr << "\nError opening " << File << endl;
return false;
}
return true;
}
};

/* the MAIN function */
int main() {
book b;

while (b.Menu())
;

return 0;
}

/* member function definitions */
int book::Menu() {
cout << "\n1. Add Contact\n"
"2. Show Contacts\n"
"3. Exit\n\n"
"Choice: ";
cin >> choice;

switch (choice) {
case 1: AddEntry(); break;
case 2: ShowBook(); break;
case 3: choice = 0; break;
}
return choice;
}

void book::AddEntry() {
fstream fout(File,ios::end|ios::app|ios::binary);

if (!CheckOpen(fout))
return;
else {
Flush();
cout << "\nEnter contact name: ";
cin.getline(name,30);
cout << "Phone number: ";
cin.getline(phone,13);
cout << "Email address: ";
cin.getline(email,30);

fout.write((char*)this,sizeof(*this));
fout.close();
}
}

void book::ShowBook() {
fstream fin(File,ios::in|ios::binary);
book temp;

if (!CheckOpen(fin))
return;
else {
SearchMenu();
bool foundmatch = false;
cout << "\n----- DISPLAYING CONTACTS -----\n";
while (fin.read((char*)&temp,sizeof(temp)) && !fin.eof()) {
if (Found(temp)) {
temp.Print();
foundmatch = true;
}
else if (srchtype == 4) {
temp.Print();
foundmatch = true;
}
}
if (!foundmatch)
cout << "\nNo matching entries found!\n";
cout << "\n----- FINISHED DISPLAYING -----\n";
fin.close();
}
}

void book::Print() {
cout << "\n Name: " << name << endl;
cout << " Phone: " << phone << endl;
cout << " Email: " << email << endl;
}

bool book::Found(book &temp) {
if (srchtype == 1 && strstr(temp.name,srchstr) ||
srchtype == 2 && strstr(temp.phone,srchstr) ||
srchtype == 3 && strstr(temp.email,srchstr))
return true;
return false;
}

void book::SearchMenu() {
cout << "\nSearch by:\n"
"1. Name\n"
"2. Phone#\n"
"3. Email\n"
"4. Show All\n\n"
"Choice: ";
(cin >> srchtype).get();
if (srchtype != 4) {
cout << "Enter the search value: ";
cin.getline(srchstr,30);
}
}

[QuestionC]

I don't really know C++ too well, but this is interesting enough to try.

//these are only visible by class book and its member functions 
typedef struct __book
{
 int choice;
 char *File; 
 char name[30]; 
 char phone[13]; 
 char email[30]; 
 int srchtype; 
 char srchstr[30];
} book;
// I get the feeling there actually is a way to make the elements of
//  this structure invisible to anything outside class book, but am 
//  not sure.  As is, anyone can access these elements, although I
//  don't see that as a big problem.

//this constructor is called whenever an object of 
//class book is created to initialize our variables 
book * initBook (void)
{
 book * b = malloc (sizeof (book));
 b -> File = malloc (14 * sizeof (char));
 strcpy (b -> File, "addresses.dat";
 b -> choice = 0;
}
// This is prolly the biggest difference the implementations 
//  will have.  For this, you will have to initialize your book as
//  book * b = initBook (); instead of 
//  book b;


void Flush (void)
{
 int c;
 for (c = 0; c != '\n'; c = getchar());
 return;
}

int Menu(book * b)
{ 
 printf ("\n1. Add Contact\n" 
 "2. Show Contacts\n" 
 "3. Exit\n\n"
 "Choice: "); 
 scanf ("%d", &b -> choice);

 switch (b -> choice) { 
  case 1: AddEntry(b); break; 
  case 2: ShowBook(b); break; 
  case 3: b -> choice = 0; break; 
 } 
 return b -> choice; 
} 

void AddEntry (book * b)
{ 
 FILE * f;
 f = fopen (b -> File, "ab"); // I'm not too sure about the ab

 // Not gonna bother implementing this helper function, so let's
 //  pretend the file always opens.
 //if (!CheckOpen(fout)) 
 //return; 
 //else { 

 Flush();
 printf ("\nEnter contact name: ");
 fgets (b -> name, 30, f);
 // Similar changes for other entries...
 //cout << "Phone number: "; 
 //cin.getline(phone,13); 
 //cout << "Email address: "; 
 //cin.getline(email,30); 

 // I have no idea of what this line does...
 //fout.write((char*)this,sizeof(*this)); 
 fclose (f); 
}

Blegh, that's hard. Actually, the main function is pretty important to see how it will change too...

int main() {
 book * b; // C uses pointers....
 b = initBook ();

 while (Menu(b)) ; 

 return 0; 
}

Pretty much just have to change it so that you pass the pointer to be from every function to function, change your input and output calls to use C functions, and instead of just using the names of the private variables of class book, you have to use book -> variableName.

It really isn't difficult if you know C, it's just awfully tedius.

[Unregistered]

Tried to compile, but still have errors, about invalid external type for AddEntry and ShowBook. Also errors about missing ; before type , as shown below:
NOt too sure about the file "ab''s function as well.

ERRORS:

// switch (b -> choice)
// {
// case 1: int AddEntry(b) ; break; // <----- missing ;
// before 'type'
// case 2: int ShowBook(b) ; break; // <----- missing ; //before 'type'
// case 3: b -> choice = 0 ; break;
}

Start of Program:

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
typedef struct __book
{
int choice;
char *File;
char name[30];
char phone[13];
char email[30];
int srchtype;
char srchstr[30];
} book;
book * initBook (void)
{
book * b = malloc (sizeof (book));
b -> File = malloc (14 * sizeof (char));
strcpy (b -> File, "addresses.dat");
b -> choice = 0;
return 0;
}
// This is prolly the biggest difference the implementations
// will have. For this, you will have to initialize your book as
// book * b = initBook (); instead of
// book b;


void Flush (void)
{
int c;
for (c = 0; c != '\n'; c = getchar());
return;
}

int Menu(book * b)
{
printf ("\n1. Add Contact\n"
"2. Show Contacts\n"
"3. Exit\n\n"
"choice: ");
scanf ("%d", &b -> choice);

switch (b -> choice)
{
case 1: int AddEntry(b) ; break;
case 2: int ShowBook(b) ; break;
case 3: b -> choice = 0 ; break;
}
return b -> choice;
}

void Add_an_Entry (book * b)
{
FILE * f;
f = fopen (b -> File, "ab"); // I'm not too sure about the ab

// Not gonna bother implementing this helper function, so let's
// pretend the file always opens.
//if (!CheckOpen(fout))
//return;
//else {

Flush();
printf ("\nEnter contact name: ");
fgets (b -> name, 30, f);
printf ("\nEnter phone number: ");
fgets (b -> phone, 13, f);
printf ("\nEnter email address: ");
fgets (b -> email, 30, f);

// I have no idea of what this line does...
//fout.write((char*)this,sizeof(*this));
fclose (f);
}
main()
{
book * b;
b = initBook ();

while (Menu(b)) ;

return 0;
}

[Unregistered]

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