// Chapter 4, pp 174 - 177
// Demonstrates SaveList and RestoreList;
// includes DisplayList.
#include <fstream.h>  // includes iostream.h
#include "boolean.h"

const int NAME_LENGTH = 12;
typedef char nameType[NAME_LENGTH];

typedef struct node* ptrType;  //ptr to node
struct node
{  int     Data;
   ptrType Next;
}; // end struct

void SaveLinkedList(ptrType Head, nameType SaveFileName)
// --------------------------------------------------------------
// Saves a linked list's data in a binary file of integers.
// Precondition: Head points to the linked list.
// SaveFileName is the name of an external general file to
// be created.
// Postcondition: The binary file SaveFileName of integers
// contains the linked list's data. The file is closed;
// Head and the linked list are unchanged.
// --------------------------------------------------------------
{
   ofstream F(SaveFileName, ios::binary); // output binary file

// traverse the list to the end, writing out each item
   for (ptrType Cur = Head; Cur != NULL; Cur = Cur->Next)
      F << Cur->Data << " ";
      //without the above " ", the integers 4, 2, 8, 6
      // are read back as one integer 4286.

   F.close();
}  // end SaveLinkedList

void RestoreLinkedList(ptrType& Head, nameType SaveFileName)
// ---------------------------------------------------------
// Creates a linked list from the data in a binary file.
// Precondition: SaveFileName is the name of an existing
// external binary file of integers.
// Postcondition: Head points to the created linked list;
// if the file is empty, Head is NULL. The file is unchanged
// and closed.
// ---------------------------------------------------------
{
   int NextValue;
   ifstream F(SaveFileName, ios::binary); // input binary file

   if (F >> NextValue)                    // is file empty?
   {  // file not empty:
      // add the first integer to the list
      Head = new node;
      Head->Data = NextValue;
      Head->Next = NULL;
      ptrType Tail = Head;

      // add the remaining integers to the linked list
      while (F >> NextValue)
      {  Tail->Next = new node;
	 Tail = Tail->Next;
	 Tail->Data = NextValue; 

	 Tail->Next = NULL;
      }  // end while
   }  // end file not empty

   else
      Head = NULL; // file is empty: return empty list

   F.close();
}  // end RestoreLinkedList

void DisplayList(ptrType Head)
// --------------------------------------------------------------
// Displays the data in a linked list.
// Precondition: Head is a pointer variable that points to
// the linked list.
// Postcondition: Displays the data in the linked liste.
// Both Head and the list are unchanged.
// --------------------------------------------------------------
{
   // Loop invariant: Cur points to the next node to be displayed
   for (ptrType Cur = Head; Cur != NULL; Cur = Cur->Next)
   cout << Cur->Data << "\n";
} // end DisplayList

// ******SAMPLE MAIN PROGRAM******
main()
{
   ptrType LLHead, NewHead, TempPtr;
   booleanType Success;

   // create a list of integers in any order
   LLHead = NULL;
   LLHead = new(node);
   LLHead->Data = 4;
   TempPtr = LLHead;
   TempPtr->Next = new node;
   TempPtr = TempPtr->Next;
   TempPtr->Data = 2;
   TempPtr->Next = new node;
   TempPtr = TempPtr->Next;
   TempPtr->Data = 8;
   TempPtr->Next = new node;
   TempPtr = TempPtr->Next;
   TempPtr->Data = 6;
   TempPtr->Next = NULL;

   cout << "The current list is:" << "\n";
   DisplayList(LLHead);

   // save the list in a general file
    SaveLinkedList(LLHead, "C4LL.DAT");
   cout << "\nGeneral File written.\n";

   // create a list from the data in the file
    RestoreLinkedList(NewHead, "C4LL.DAT");

    cout << "This is the restored list of integers, as read from the file:\n";
    DisplayList(NewHead);

    cout << "Program End.\n";

    return(0);
}  // end main