WIP Borland C Doubly linked list

Hi all!

I need to create a programm wich represents doubly linked list. It should do the following
1. Create new list
2. Add new structure
3. Delete selectes dtructure
4. Load existing list from file
5.Save list to file.

It very difficult for me to understand. I've tryed to write some code. But I need somebody to help me to complete my project. I need just a little help.

Code:

#include <stdio.h> #include <conio.h> #include <alloc.h> #include <string.h> struct item //the structure {char name[10]; int prc; int col; // there are 3 elements in the structure name, prc, col struct item *prev; // to previous structure struct item *next; // to next structure }; void build(void); // creates new structure void view(item *); // list struct item *head,*tail; // pointers main() { //поехали! build(); //so we create new structure list(head); // then we can list free(head); } void build(void) //create new node function {item *p,*pr; // pr=NULL; printf("Creating new node\n\n"); do { p=(item *)malloc(sizeof(spis)); printf("Поле Name: "); //So we begins to fill our structure gets(p->name); //fills the name element of the structure item p->v1=pred; if (pr!= NULL) pr->next=p; else head=p; pr=p; puts(" Finish- <esc>"); }

Can somebody show me how to fill prc and cal elemens of the structure.
And then show them

Start by properly indenting all of your code, adding the appropriate whitespace, checking your backets match up, make sure you declare main correctly as int, and don't cast the result of malloc.

Heres a good start.....

Code:

#include <stdio.h> #include <stdlib.h> #include <string.h> typedef struct Rec { char *name; int prc; int col; }Record; typedef struct node { Record r; struct node *previous; struct node *next; }Node; typedef struct list { Node *head; Node *tail; }List; List *CreateList() { List *l = calloc(1, sizeof(List)); if(l == NULL) return NULL; else { l->head = NULL; l->tail = NULL; return l; } } Node *CreateNode(char *name, int Prc, int Col) { Node *n = calloc(1, sizeof(Node)); if(n == NULL) return NULL; else { n->next = NULL; n->previous = NULL; if(name == NULL) { free(n); return NULL; } else { //You may use strdup here. /*n->r.name = strdup(name);*/ //Init. n->r.name = malloc((strlen(name) + 1) * sizeof(char)); strncpy(n->r.name, name, strlen(name)); n->r.name[strlen(name)] = '\0'; n->r.prc = Prc; n->r.col = Col; //Return the node. return n; } } } //Add a new node to the end of the list int AddNode(List *l, char *Nname, int Prc, int Col) { if(l == NULL) return -1; if(Nname == NULL) return -2; Node *n = CreateNode(Nname, Prc, Col); if(n) { if(l->head == NULL) l->head = l->tail = n; else { n->previous = l->tail; l->tail->next = n; l->tail = n; } return 0; } else return -3; } void PrintList(List *l) { Node *temp = l->head; printf("Printing List:\n"); while(temp) { printf("%s\t%d\t%d\n", temp->r.name, temp->r.prc, temp->r.col); temp = temp->next; } } int main(int argc, char *argv[]) { List *l = CreateList(); AddNode(l, "Nick", 24,45); AddNode(l, "Tom", 26,85); AddNode(l, "Snow", 56,42); PrintList(l); system("PAUSE"); return 0; }

There are some errors I cant resolve. Does this code written for Borland C?

if you want help with solving errors for any code tell us what the errors are

> Does this code written for Borland C?
Unfortunately for you, Bokarinho chose to write in C99 style, which is the very latest standard for C. Your really old compiler is going to have trouble with this.

A couple of things to fix
1. Change all the // comments to /**/ comments.
2. Node *n = CreateNode(Nname, Prc, Col);
needs to be split into a declaration and an assignment.

@ Bokarinho
> strncpy(n->r.name, name, strlen(name));
> n->r.name[strlen(name)] = '\0';
Why not do just strcpy() in this case, since what you have is functionally identical.

Quote:

Originally Posted by Salem

> Does this code written for Borland C?
Unfortunately for you, Bokarinho chose to write in C99 style, which is the very latest standard for C. Your really old compiler is going to have trouble with this.

A couple of things to fix
1. Change all the // comments to /**/ comments.
2. Node *n = CreateNode(Nname, Prc, Col);
needs to be split into a declaration and an assignment.

@ Bokarinho
> strncpy(n->r.name, name, strlen(name));
> n->r.name[strlen(name)] = '\0';
Why not do just strcpy() in this case, since what you have is functionally identical.

Just to break the monotony..............
LOL

Ok I resolved practically all my problems with my programm. The code of Bokarinho its just what I want but I should use my code instead :( Now I need to realyze saving and loading from file. Can somebody help me to develop save and load functions for my code. I need it to complete my project.
here is my code

Code:

include <stdio.h> #include <conio.h> #include <alloc.h> #include <string.h> struct item //name of the structure {char name[20];int prc; int col; //structure of the thread struct item *prev; struct item *next; }; void build(void); //builds new list void view(item *);//view list void add(item *); //add to list void save(FILE *);//Save list to file struct item *head,*tail; main(){int c; FILE *in;..... void build(void) {item *p,*pr; pr=NULL; do { p=(item *)new item; clrscr(); printf("Name а : "); scanf("%s",&p->name); printf("Prc. : "); 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("\nFinish <esc>"); } while (getch()!=27); tail=p; tail->next=NULL; } void view(item *p) {int i=1; clrscr(); "); if (p==head) while (p != NULL) {printf("\n%-2d%-15s\t%3d\t%3d",i,p->name, p->prc, p->col); i++; p=p->next; } else puts("Error "); getch(); }

I think save funktion should look like this but it just a fought

Code:

void save(FILE *); p==head; in=fopen("data.txt",wb"); clrscr(); printf("\nSave"); while (p != NULL) fwrite(&item,sizeof(item),1,in); p=p->next; getch(); }

>Can somebody help me to develop save and load functions for my code
You could save the linked link in two ways
1. You could just save the content of the each node in to the text file.
2. You could save each node to a binary file.

You coud use either of thise tech. To save a linked list.

Code:

/* Check out what you need sending here as a prameter */ void save(....) { p==head; in=fopen("data.bat","wb"); /* Don't use this function */ clrscr(); printf("\nSave"); while (p != NULL) { fwrite(&item,sizeof(item),1,in); p=p->next; } getchar(); }

ssharish

I need to save and load from binary file
This coda has too many errors. And btw what should i send as a parameters?

Well as far as i was aware i dint meant that code would work either. I throught it would just be an idea or so. You will have to work along with that code.

The parameter might be up to you. If you have declared your head pointer as global then u dont need sending that as a parameter. But other than that, if you think you need sending the FILE pointer you could send that. Or you could just send the file name and the head pointer.

And in the function u could open the file using the filename sent and starting writing on to.

ssharish

Can you help me to make it work? I know this is not so difficult task but its too difficult for me

Post the code which you have got so far. I mean the save function

ssharish

Ok thats the way I immagine that

Code:

struct item //name of the structure {char name[20];int prc; int col; //structure of the thread struct item *prev; struct item *next; }; void build(void); //builds new list void view(item *);//view list void add(item *); //add to list void save(FILE *);//Save list to file prototype struct item *head,*tail;

Then in function main I define a variable for file

Code:

main(){int c; FILE *in;

And here the save function itself

Code:

void save(FILE *in) { p==head; //p -mean pointer in=fopen("data.txt","wb"); //create or open file data.txt while (p != NULL) //and untill the NULL of the list { fwrite(&item,sizeof(item),1,in); //write one structure size of item to file in binary mode p=p->next; //move next structure } getchar(); }

What to send as a parameters? THe code I've posted before is the whole code exept of menu.

Quote:

Originally Posted by BCWarrior

Ok thats the way I immagine that

Code:

struct item //name of the structure {char name[20];int prc; int col; //structure of the thread struct item *prev; struct item *next; }; void build(void); //builds new list void view(item *);//view list void add(item *); //add to list void save(FILE *);//Save list to file prototype struct item *head,*tail;

Then in function main I define a variable for file

Code:

main(){int c; FILE *in;

And here the save function itself

Code:

void save(FILE *in) { p==head; //p -mean pointer in=fopen("data.txt","wb"); //create or open file data.txt while (p != NULL) //and untill the NULL of the list { fwrite(&item,sizeof(item),1,in); //write one structure size of item to file in binary mode p=p->next; //move next structure } getchar(); }

What to send as a parameters? THe code I've posted before is the whole code exept of menu.

I dont know why you are still confused. Its simple as many people told you, i worked with text files so i can easily see the file without using a special program to read binary files or without afterwards loading it into memory to see if it succeeded. So the answer is the last function in my previous code.

Code:

//--------------------------------------------------------------------------- #include <stdio.h> #include <stdlib.h> #include <string.h> #include <ctype.h> #include <conio.h> #define BUFSZ 512 #pragma hdrstop //--------------------------------------------------------------------------- #pragma argsused typedef struct Rec { char *name; int prc; int col; }Record; typedef struct node { Record r; struct node *previous; struct node *next; }Node; typedef struct list { Node *head; Node *tail; }List; List *CreateList(void) { List *l = calloc(1, sizeof(List)); if(l == NULL) return NULL; else { l->head = NULL; l->tail = NULL; return l; } } Node *CreateNode(char *name, int Prc, int Col) { Node *n = calloc(1, sizeof(Node)); if(n == NULL) return NULL; else { n->next = NULL; n->previous = NULL; if(name == NULL) { free(n); return NULL; } else { //You may use strdup here. /*n->r.name = strdup(name);*/ //Init. n->r.name = malloc((strlen(name) + 1) * sizeof(char)); strncpy(n->r.name, name, strlen(name)); n->r.name[strlen(name)] = '\0'; n->r.prc = Prc; n->r.col = Col; //Return the node. return n; } } } //Add a new node to the end of the list int AddNode(List *l, char *Nname, int Prc, int Col) { Node *n = NULL; n = CreateNode(Nname, Prc, Col); if(n) { if(l->head == NULL) l->head = l->tail = n; else { n->previous = l->tail; l->tail->next = n; l->tail = n; } return 0; } else return -3; } void PrintList(List *l) { Node *temp = l->head; printf("Printing List:\n"); while(temp) { printf("%s\t%d\t%d\n", temp->r.name, temp->r.prc, temp->r.col); temp = temp->next; } } void PrintListToFile(List *l, char *filename) { FILE *f = fopen(filename, "w"); if(f == NULL) { printf("Error, can not open '%s' file.\n", filename); return; } else { Node *n = l->head; char *Message = "Printing List Nodes....."; fprintf(f,"%s\n", Message); while(n) { if(fprintf(f,"%s\t%d\t%d\n", n->r.name, n->r.prc, n->r.col) > 0) n = n->next; } fclose(f); } } int main(int argc, char *argv[]) { List *l = NULL; l = CreateList(); AddNode(l, "Nick", 24,45); AddNode(l, "Tom", 26,85); AddNode(l, "Snow", 56,42); PrintList(l); PrintListToFile(l, "list.txt"); printf("Hit any Key to continue........\n"); getch(); return 0; } //---------------------------------------------------------------------------

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 %-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; }

> Right or not?

You aren't paying attention to what anyone is doing for you. A function like load() needs to return anything it builds up from nothing to its caller. Please, please return valid pointers to new lists. If you don't do that your implementation is broken, because anything that works will be pointless after load() leaks memory and you lose access to the entire data structure.

> But what about memory? Should it be free?

Yes it should. But you have to have access to the memory you allocate in the first place. Destroying any data structure allocated on the heap is an operation that needs to be done explictly in C. Say you had a routine

void freelist( item *first );

You can write freelist by walking through a list that was passed in by the first item and freeing nodes along the way.

Only call freelist( first_item ) in load() if an error occurred and you need to clean up a half-completed list. Destroying the list in the load() routine for any other reason breaks your implementation.

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.

I take it the code you posted earlier doesn't compile - it has several missing semi-colon's, and two extraneous curly braces.

When this bit of code starts, p is not initialized, so it will be some random garbage - freeing a "list" of random garbage is absolutely detrimental to the stability of the system.

Code:

while (p!=NULL){ //free memory p=p->next; free(p); }

Code:

p=fread(p,sizeof(item),1,in); //read one item from file.

Setting p to the value read from the file is perhaps not such a good idea, as p is a pointer, and the return from "fread" is the number of items successfully read.

You will probably also find that you attempt to read one more item than there is in the file. If you check the result from fread() [but not by putting the result into a pointer], you will have a more reliable way to ensure that your function doesn't read any more data than it should.

You are not including the code to build the linked list in your loop to read the data from the file, you need to move it up to before the "while" end of your do-while-loop.

--
Mats

This is my new version of load function. The last function I need to add to my project .More then one week passed And Im still moving in wrong direction.
Can somebody help me!
I might be stupid but im not lazy! And I have only 2 days to complete :( Please don't leave me.

Code:

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

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.

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?

Quote:

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.

OK, but you're still reading from a file opened for writing

> fread(p, sizeof(item), 1, in);
> scanf("%s",&p->name);
I thought you just read the information from the file, why are you also reading from the user, and overwriting what you read from the file?

Quote:

Originally Posted by Salem

OK, but you're still reading from a file opened for writing

> fread(p, sizeof(item), 1, in);
> scanf("%s",&p->name);
I thought you just read the information from the file, why are you also reading from the user, and overwriting what you read from the file?

According your notice i changed file mode to rb
so now it looks like this

Code:

in=fopen("data.txt","rb"); do { p=(item *)new item; fread(p, sizeof(item), 1, in);

I still can't understand

1.So I open file
2.And read 1 structure sizeof(item) from file
3. But what to do next?

If im not mistaken struct item consist of data and pointers? so what to do with them? or they wasnt saved with data?
I decided to use scanf. Is this right choice? Or the procedure shouold be different?
I have too many questions but I can't find answers anythere :(

Code:

in=fopen("data.txt","rb"); do { p=(item *)new item; fread(p, sizeof(item), 1, in); scanf("%s",&p->name); scanf("%d",&p->prc); scanf("%d",&p->col); p->prev=pr; if(pr != NULL) pr->next=p; else head=p; pr=p; } while (!feof(in)); tail=p; tail->next=NULL; }

I would suggest you make a clear distinction between reading the data (from whatever source) and placing that data in the list.

Code:

typedef struct { int data; } data; typedef struct list_tag { struct list_tag *next; data data; } list; list *append ( list *oldlist, data data ) { list *newlist = malloc( sizeof *newlist ); if ( newlist != NULL ) { newlist->data = data; newlist->next = NULL; if ( oldlist == NULL ) { /* a new list */ oldlist = newlist; } else { /* non empty list, seek the tail and append */ list *tail = oldlist; while ( tail->next != NULL ) tail = tail->next; tail->next = newlist; } } return oldlist; } list *readFromUser ( void ) { list *list = NULL; data data; while ( scanf("%d",&data.data) == 1 ) { list = append( list, data ); } return list; } list *readFromFile ( char *filename ) { FILE *fp = fopen( filename, "rb" ); list *list = NULL; data data; while ( fread( &data, sizeof data, 1, fp ) == 1 ) { list = append( list, data ); } fclose( fp ); return list; }

Reading functions don't care how the detail of the list works.
The list functions don't care where the data comes from.

So I need to rewrite the add function to append data from user as well as from file?
what does the list mean in your code?

List means the list you want to create.

In main() say,
list *mylist = readFromFile( "myfile.dat" );

btw is this single linked list?
Oh

Yes it is, but that doesn't change the overall approach.

This code dose not produce any errors. It creates list and fills is, then saves to file and try to load. I tryed to printf the content loaded from file. Works fine. But is it podssible to do such a way

read one structure from file and use it to fill new structure? till the end of file
Also I wounder does my clear memory function work?

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(struct item *); void load(void); struct item *head,*tail; main(){ clrscr(); build(); view(head); getch(); clrscr(); printf("\nfrom file"); load(); view(head); getch(); } void build(void) {item *p,*pr; pr=NULL; do { p=(item *)malloc(sizeof(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 load(void) { item *p,*pr; FILE *in; while(p!=NULL) { p=p->next; //Clears memory free(p); } in=fopen("data.txt","rb"); do{p=(item *)malloc(sizeof(item)); fread(p,sizeof(item),1,in); p->prev=pr; if(pr != NULL) pr->next=p; else head=p; pr=p; printf("Esc"); } while (!feof(in)); tail=p; tail->next=NULL; } void view(item *p) { int i=1; FILE *in; clrscr(); in=fopen("data.txt","wb"); if( in != NULL ) { while (p != NULL) { printf("\n %-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; } }

Or can you help me to change variables in your append and load functions to mine which i used in my code? Such as item p next prev etc.
Please

I find your lack of braces and poor indentation too hard to read.

But the loop calling free() is most definitely wrong.

Can load from file function be realized such a way. If im not misstaken I read one structure from file to memory. Then if I want to prin it I can use something like this

printf("\n %d %s\t%d\t%d",i,p->name, p->prc, p->col)

so p->name, p->prc, p->col mean that I can read them from memory. But can I use them to create new item of the list? If yes how to get them an assign to new thread

I though it can be realized such a way bout its just fought. Can somebody answer my questions?

Code:

void load(void) {item *p, *ni, *pr; FILE *in; p = head; while(p!=NULL) { item *pTemp; pTemp=p->next; free(p); p = pTemp; } in=fopen("data.txt","rb"); do{ ni=(item *)malloc(sizeof(item)); fread(p,sizeof(item),1,in); p->name=ni->name; p->prc=ni->prc; p->col=ni->col; ni->prev=pr; if(pr != NULL) pr->next=p; else head=ni; pr=ni; printf("Esc"); } while (!feof(in)); tail=ni; tail->next=NULL; }

> printf("\n %d %s\t%d\t%d",i,p->name, p->prc, p->col)
This ALWAYS reads from memory.
It doesn't care how you wrote to that memory.

You could do
p->col = 0;

Or
scanf("%d", &p->col );

Or
fread( .... )

Or
p->col = aFunctionReturningInt();

It's all the same.

ni=(item *)malloc(sizeof(item));
fread(p,sizeof(item),1,in);
p->name=ni->name;
p->prc=ni->prc;
p->col=ni->col;
ni->prev=pr;
This is the wrong way round.
You read into where p points, then you OVERWRITE p with the uninitialised junk in ni.