Thread: WIP Borland C Doubly linked list

Code:

fwrite(&item,sizeof(item),1,in);

change it to write each node to file. So for example

Code:

fwrite(p,sizeof(item),1,in);

This writes each node on to file. The first parameter is the actual node which u need to write and the next sizeof the node which u wanted to write. And next the no of nodes which u need to write in the above case its just one cos, you are writing just on node. And the last is the File pointer.

And dont forget to close the file.

ssharish

OK I decided to simlify the code and join save and view functions. Of course it will be wonderful if there was no any errors. I put compiller messages near the lines. What does it want from me? %|

Code:

#include <stdio.h>
#include <conio.h>
#include <alloc.h>
#include <string.h>
struct item
{char name[20];int prc; int col;
  struct item *prev;
  struct item *next;
};
void build(void);
void view(item *,FILE *in);
struct item *head,*tail;
main(){
clrscr();
build();
view(head); //Too few parameters in call to 'view(item far*,struct far*)' in function main()
}
void build(void)
{item *p,*pr;
  pr=NULL;
    do { p=(item *)new item;
    clrscr();
    printf("Name : ");
    scanf("%s",&p->name);
    printf("\nPrc : ");
    scanf("%d",&p->prc);

    printf("\nCol: ");
    scanf("%d",&p->col);
    p->prev=pr;
  if(pr != NULL)
    pr->next=p;
  else
    head=p;
    pr=p;
    printf("Esc");
}
while (getch()!=27);
    tail=p;
    tail->next=NULL;
}
void view(item *p,FILE *in)
{int i=1;
clrscr();
in=fopen("data.txt","wb"); //Cannot assign 'unsigned int' to 'struct far*' in function view(item far*,struct far*)
  while (p != NULL)
  {printf("\n %-2d   %-15s\t%3d\t%3d",i,p->name, p->prc, p->col);
  in=fwrite(p, sizeof(item),1,in); //Parameter 'in' is never used in function view(item far*,struct far*)
  i++;
  p=p->next;
    getch();
}
}

Code:

#include <stdio.h>
/* #include <conio.h> */
#include <alloc.h>
#include <string.h>
#include <errno.h>

struct item
{
   char name[20];
   int prc,col;
   struct item *prev;
   struct item *next;
};

void build(void);
void view(struct item *);

struct item *head, *tail;

int main()
{
     /* clrscr(); */
    build();
    view(head); 
    
    getchar();
    return 0;
}

.
.
.
.
void view(item *p)
{
     int i=1;
     FILE *in;
     
     /* This is a non standard function, DONT USE IT */
     clrscr();
     
     in=fopen("data.txt","wb"); 
     
     if( in != NULL )
     {     
         while (p != NULL)
         {
               printf("\n &#37;-2d   %-15s\t%3d\t%3d",i,p->name, p->prc, p->col);
               
               if(!fwrite(p, sizeof(item),1,in))
               {
                   perror("fwrite");
                   getchar();
                   fclose(in);
                   return; 
               }
               i++;
               p = p->next;
         }
         fclose(in);
     }
     else
     {
         printf("Error: File cannot be created/opened\n");
         printf("Press any key to continue...\n");
         getchar();
         return;
     }
}

I will leave the build with you. Look through it, what error checking you need to do and what need passing as parameter.

ssharish

Thanx a lot! After some corrections the code works the way i want. Now my last problem is loading from file. Of course I don't exactly know how to realize it. But something tells me that It just the same as a build a list but the function should take the data from saved file.
Right or not? But what about memory? Should it be free?

Code:

void load(void)
{item *p,*pr;
FILE *in;
in=fopen("data.txt","wb");
  pr=NULL;
    do { p=(item *)new item;
    fread(p,sizeof(item),1,in);
    p->prev=pr;}
    while (!feof(in))
  if(pr != NULL)
    pr->next=p;
  else
    head=p;
    pr=p;
}
    tail=p;
    tail->next=NULL;
}

having spended a couple of hours. I still have no idea . I've tryed to add free memory ability. It seems to me that I work in wrong direction.

Code:

void load(void)  //still haveing problems with parameters
{item *p,*pr;   //I tryed to modify the build function
FILE *in;         //Defines file
while (p!=NULL){ //free memory
p=p->next;
free(p);
}
in=fopen("data.txt","wb");   //opens file
  pr=NULL;
    do
    {p=(item *)malloc(sizeof(item))
    p=fread(p,sizeof(item),1,in); //read one item from file.
    p->prev=pr;}
    while (!feof(in))
    }
  if(pr != NULL)
    pr->next=p;
  else
    head=p;
    pr=p;
}
    tail=p;
    tail->next=NULL;
}

Please can somebody help me? I have only a few days to compete my project.

get a compiler.

Cprogramming.com: How to Get Started with C++

Bad joke %(

so you have one? did you try compiling it?

It to me seems that I missed the time when computers begun to do everything right without man.
My problem Is that I have read lots of articles about lists and bin files And about methods of saving and reading. But I can't find any example about saving 2-linked lists. So I have a lot of blanks in my knowledge And I still cant fill them.

Originally Posted by Salem

Code:

void load(head)
{item *p *pr;
FILE *in;
in=fopen("data.txt","wb");
fread(p, sizeof(item), 1, in);
while(!feof(in))
{scanf("
void load()

Does this mess even compile?

Also, why are you trying to read from a file opened in "wb" mode?

Ive corrected the code. And remove that. This was a part of one of my thoughts about function load.