Creating data, but data nowhere

[Holymanus]

Hello, i got some problem, when creating data trought another .c file (taken from header) which doesnt contain any main(). So question is: what to do that it will not dropping my data somewhere. Use some static or something else?

My program is linked from files:

tab.h 
tab.c (here is #ifndef #include "serverapp.h" #endif)
serverapp.h
serverapp.c (here is main() and #ifndef #include "tab.h" #endif)

so i feel that im using tab.c (tab.h) wrong when creating througth that "data" - structures

[laserlight]

Post the smallest and simplest compilable program that demonstrates the problem.

[CommonTater]

Put the definitions of your data structures in the .h file.
Also look at the keyword .. extern .. which lets you access data across source pages.

[Holymanus]

/*
 * tab.h
 *
 *  Created on: 21.11.2010
 *      Author: Martin
 */

#ifndef TAB_H_
#define TAB_H_

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
// column is item of list of names of columns
// Column *next - pointer on next item in list

typedef struct Column {
	char name[10];
	struct Column *next;
	//struct Column *previous;
} column;

// item of row, items in row complete list
typedef struct Item {
	int value;
	//struct Column *itemof;
	struct Item *next;
} item;

// row is pointer on list of items
typedef struct Row {
	item *first_item;
	//struct Column *itemof;
	struct Row *next;
} row;

// tab is "pointer" on head row inculde count of columns and names of them
typedef struct Tab {
	char name[10];
	int columns_count;
	int rows_count;
	column *first_col_name;
	struct Tab *next;
	row *first_row;
	row *spec_iter_row;
	//struct List *previous;
} tab;

void print_row(tab *which_from, row *for_print);

column *create_list_of_names(char *column_names);

tab *create_tab(char *name, char *column_names);

int *create_row(int values[], char tab_name[]);

int delete_row(tab *tab_temp,row *for_delete);

void delete_all_rows(char tab_name[]);

void delete_from(char tab_name[], char column_name[], int value);

void delete_tab(char tab_name[]);

int delete_all(char passwd[]);

tab *find_tab(char tab_name[]);

row *find_value(char tab_name[], char column_name[], int value, int ctr);

void select_from(char tab_name[], char column_name[], int value);

void print_all(char tab_name[]);

//void add_item(item **head, char *name, int age);
extern int tab_count;
extern tab *first_tab;
extern tab *last_tab;

#endif /* TAB_H_ */

[Holymanus]

so if i understood right, i will use this externs there where i want to save them yes ?

[Salem]

Well you get past the need to "store some magic internal variable" if you arrange the interface like so.

tab *create_tab(char *name, char *column_names);
void print_tab(tab *tab);
void delete_tab(tab *tab);

The create function returns a tab*, and ALL other interfaces receive a tab*

Follow something like fopen() (returns a 'token' as a FILE*), and everything else (fclose, fread, fgets, etc etc) all take a FILE* as a parameter.
What a FILE* actually is is irrelevant to the users of the service.

[CommonTater]

so if i understood right, i will use this externs there where i want to save them yes ?

The extern keyword simply means "created elsewhere"...

//first.c
int x; 


// second.c
extern int x;

second.c has access to x from first.c Placing them in a header is just a convenience so they are available everywhere the header is included.