I have a linked list like this http://pastebin.com/bwF3jLb6 . The problem i am facing is i have initialized the list head and
then i am doing malloc for that struct object. What i need is i want to make struct abc_st *r as head of linked list and other nodes after it.
typedef struct abc {
char client_id[18];
char mac[18];
st_list_head list;
}abc_st;
abc_st* check_fields (abc_st *ptr)
{
char cmd[500];
MYSQL_RES *result;
MYSQL_ROW row;
int num_rows;
abc_st *r=NULL,*temp=NULL;
INIT_LIST_HEAD(&r->list); // i have intialized the head here
sprintf(cmd, "SELECT * FROM ABCD_TABLE WHERE MAC = %.4x", ptr->mac);
/* Running the sql query to check for fields with value in database */
if (mysql_query(abc_db.db_handle, cmd)) {
num_rows = -1;
goto done;
}
result = mysql_store_result(abc_db.db_handle);
if (result == NULL) {
num_rows = -1;
goto done;
}
num_rows = mysql_num_rows(result);
while ((row = mysql_fetch_row(result)))
{
r= (abc_st *)malloc(sizeof(abc_st));
memcpy(r->mac,row[1],strlen(row[1])+1);
memcpy(r->client_id,row[0],strlen(row[0])+1);
How should i use list_add ?
//list_add(struct list_head *new, struct list_head *head) //prototype of list_add
// list_add(&temp->list,&r->list); //it will go wrong here, i want to make r(structure r as head and then add other strutcure objects)
// r->link = NULL;
//list_add(r, ptr);
}
done:
mysql_free_result(result);
return r;
}
#ifndef __LIST_H
#define __LIST_H
struct list_head {
struct list_head *next, *prev;
};
typedef struct list_head st_list_head;
#define INIT_LIST_HEAD(ptr) do { \
(ptr)->next = (ptr); (ptr)->prev = (ptr); \
} while (0)
/*
* __list_add: insert new between prev and next.
*/
static inline void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next)
{
next->prev = new;
new->next = next;
new->prev = prev;
prev->next = new;
}
/**
* list_add: add a new entry to the end of the list.
*/
static inline void list_add1(struct list_head *new, struct list_head *head)
{
__list_add(new, head->prev, head);
}
/*
*__list_del: making the prev/next entries point to each other.
*/
static inline void __list_del(struct list_head *prev, struct list_head *next)
{
next->prev = prev;
prev->next = next;
}
/**
* list_del: deletes entry from list.
*/
static inline void list_del(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
entry->next = (void *) 0;
entry->prev = (void *) 0;
}
/**
* list_empty: check is list is empty.
*/
static inline int list_empty(struct list_head *head)
{
return head->next == head;
}
/**
* list_entry: retrieve the container struct.
*/
#define list_entry(ptr, type, member) \
((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
/**
* list_for_each: traverse through the list.
*/
#define list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); \
pos = pos->next)
/**
* list_for_each_delete: traverse through the list with safe delete
*/
#define list_for_each_delete(pos, n, head) \
for (pos = (head)->next, n = pos->next; pos != (head); \
pos = n, n = pos->next)
#endif
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