не работает вывод\ввод списков из фаила

[mego4el]

пожалуйста помогите разобраться что я сделал не так.. не хочет выводить\вводить из\в фаил списки, а список у меня кольцевой двусвязный, спасибо заранее!

#include <iostream>
#include <windows.h>
#include <stdio.h>
using namespace std;

const int color=system("color F0");
int menu();

struct leaf
{
	char sn[50];  //student name
	int sid;      //student number
};

struct list
{
	leaf x;
	list *next;
	list *prev;
};


list *list_end=NULL;          
list *dobav_nach(list *p);  //dobavit v nachalo
list *udal_nach(list *p);    //udalit iz nachala
list *dobav_proizv(list *p);  //dobavit v proizvolnoe mesto
list *udal_proizv(list *p);  //udalit iz proizvolnogo mesta
list *clean_list(list *p);    //ochistit spisok
void proverka(list *p);     //proverka, pust li spisok
void print(list *p);        //vyiti


int printfl(list *p, char *fname);
int readfl(list *p, char *fname);
list *dob(list *f, leaf t);

//------------------------------------------------------------

int main()
{
	list *l=NULL;
	bool ex=true;
	char FN[30];
	while (ex)
	{
		switch(menu())
		{
		case 1: l=dobav_nach(l); break;
		case 2: l=udal_nach(l); break;
		case 3: dobav_proizv(l); break;
		case 4:
			if (udal_proizv(l)==NULL)
			l=NULL;
			break;
		case 5: proverka(l); break;
		case 6: l=clean_list(l); break;
		case 7: print(l); break;
		case 8: 
			cout<<" Please write the filename:\n";
			cin>>FN;
			if (readfl(l,FN))
			{
				cout<<" File was opened!\n";
				l=list_end->next;
			}
			else 
				cout<<" ERROR: File not open\n";
			break;
		case 9:
			cout<<"Please write the filename:\n";
			cin>>FN;
			if (readfl(l,FN))
				cout<<" Successfully written to file!\n";
			else
				cout<<" ERROR: List not written to file!\n";
			break;
		case 0: ex=false; break;
		default: cout<<" DEFAULT: Please select item!"<<endl; break;
		}
	}
	return 0;
}

//-----------------------------------------------

int menu()
{
	int m;
	cout<<"\n \2\1\2\1\2\1\2\1\2\1\2\1\2\1\2\1\2\1\2\1\2\1"<<endl;
	cout<<" Please select item: \n\n";
	cout<<" 1 - Add to the top\n"; 
	cout<<" 2 - Remove from the top\n"; 
	cout<<" 3 - Add to arbitrary place\n"; 
	cout<<" 4 - Remove from arbitrary place\n";
	cout<<" 5 - Check: whether the list is empty?\n";
	cout<<" 6 - Clear the list\n";
	cout<<" 7 - Print list\n";	
	cout<<" 8 - Enter a list from file\n";
	cout<<" 9 - Withdraw a list to file\n";
	cout<<" 0 - Quit\n";
	cout<<" \2\1\2\1\2\1\2\1\2\1\2\1\2\1\2\1\2\1\2\1\2\1"<<endl<<endl;
    cout<<" ";
	cin>>m;
	return m;
}

//-----------------------------------------------

list *dobav_nach(list *p)
{
	list *t;
	t=new list;
		cout<<endl<<" PLEASE ENTER THE STUDENT NAME: ";
		cin>>t->x.sn;
	    cout<<" PLEASE ENTER THE STUDENT NUMBER: ";
	    cin>>t->x.sid;
	if (p==NULL)
	{
		t->next=t;
		t->prev=t;
		p=t;
		list_end=t;
		cout<<endl<<" ...Added successfully!\n\n";
		
	}
	else
	{
		t->next=p;
		t->prev=list_end;
		list_end->next=t;
		cout<<endl<<" ...Added successfully!\n\n";
	}
	return t;
}

//-----------------------------------------------

list *udal_nach(list *p)
{
	list *t;
	if(p==NULL)
		cout<<" Spisok pyst!";
	else
	{
		if(p==list_end)
		{
			delete p;
			p=NULL;
			list_end=NULL;
			cout<<endl<<" ...Deleted successfully!\n\n";
		}
		else
		{
			t=p;
			p=p->next;
			p->prev=list_end;
			list_end->next=p;
			delete t;
			cout<<endl<<" ...Deleted successfully!\n\n";
		}
	}
	return p;
}

//-----------------------------------------------

list *dobav_proizv(list *p)
{
	int sd;
	list *s,*t;
	if(p==NULL)
		cout<<" Spisok pyst!";
	else
	{
		t=p;
		cout<<endl<<"Vvedite nomer studenta, posle kotorogo budet vstavlen etot: ";
		cin>>sd;
		do
		{
		if(t->x.sid==sd)
			{
			s=new list;
			cout<<"Vvedite imya studenta: ";
			cin>>(s->x.sn);
			cout<<"Vvedite nomer studenta: ";
			cin>>s->x.sid;
			s->next=t->next;
			t->next->prev=s;
			s->prev=t;
			t->next=s;

			cout<<endl<<" ...Added successfully!\n\n";
			if(s->next==p)
			list_end=s;
			break;
			}
		t=t->next;
		}
	while(t!=p);
	}
	return s;
}

//-----------------------------------------------

list *udal_proizv(list *p)
{
	int sd;
	list *s,*t;
	if(p==NULL)
	cout<<" Spisok pyst!";
	else
	{
		t=p;
		cout<<endl<<"Vvedite nomer studenta, kotoruy budet udalen: ";
		cin>>sd;
	while(t->next!=p)
	{
		if(t->next->x.sid==sd)
		{

			s=t->next;
			t->next=s->next;
			s->next->prev=t;
			delete s;
			cout<<endl<<" ...Deleted successfully!\n\n";
			if(t->next==p)
			{
				list_end=t;
			}
			break;
		}
		t=t->next;
	}
	}
	return t;
}

//-----------------------------------------------

void proverka(list *p)
{
	if(p==NULL)
		cout<<endl<<" Spisok pyst!\n\n";
	else
		cout<<endl<<" Spisok ne pyst!\n\n";
}

[mego4el]

продолжение кода:

//-----------------------------------------------

list *clean_list(list *p)
{
	list *t;
	if(p==NULL)
		cout<<" Spisok pyst!";
	else
	{
		while(p!=list_end)
		{

			t=p;
			p=p->next;
			delete t;
		}
		delete p;
		p=NULL;
		list_end=NULL;
		cout<<endl<<" ...Cleaned successfully!\n\n";
	}
	return p;

}

//-----------------------------------------------

void print(list *p)
{
	list *t_p=p;
	if(t_p)
	{
		do
		{
		cout<<" \20\20\20\20\20\20\20\20\20\20\20\20\20\20\20\20\20"<<endl;
		cout<<" STUDENT NAME: "<<t_p->x.sn<<endl;
		cout<<" STUDENT NUMBER: "<<t_p->x.sid<<endl;
		cout<<" \21\21\21\21\21\21\21\21\21\21\21\21\21\21\21\21\21\n\n";
		t_p=t_p->next;
		}
	while(t_p!=list_end->next);
	}
	else
	cout<<" Spisok pyst!\n\n";
}

//-----------------------------------------------

int printfl(list *p, char* fname)
{
	FILE *Q;
	list *t=p;
	Q=fopen(fname,"wb");
	if(!Q)
		return 0;
	do
	{
		fwrite(&(t->x),sizeof(leaf),1,Q);
		t=t->next;
	}
	while(t!=p);
	fclose(Q);
	return 1;
}

//-----------------------------------------------

int readfl(list *p, char *fname)
{
	leaf t;
	FILE *Q;
	Q=fopen(fname,"rb");
	if (!Q)
		return 0;
	while((fread(&t,sizeof(leaf),1,Q))>0)
		p=dob(p,t);
	fclose(Q);
	return 1;
}

//-----------------------------------------------

list *dob(list *f, leaf n)
{
	list *t;
	if(f==NULL)
	{
		f=new list;
		f->x=n;
		f->next=f;
		list_end=f;
		return f;
	}
	t=new list;
	t->x=n;
	t->next=list_end->next;
	list_end->next=t;
	list_end=t;
	return f;
}