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Linked List

Linked list implements both double and single linked lists with variety of operations including fast sort.

Linked list structures
typedef struct gp_list_head {
        struct gp_list_head *next;
} gp_list_head;

typedef struct gp_dlist_head {
        struct gp_dlist_head *next;
        struct gp_dlist_head *prev;
} gp_dlist_head;

typedef struct gp_list {
        gp_list_head *head;
        gp_list_head *tail;
        size_t cnt;
} gp_list;

typedef struct gp_dlist {
        gp_dlist_head *head;
        gp_dlist_head *tail;
        size_t cnt;
} gp_dlist;

/* Structure to be used with a single linked list */
struct user_struct {
        gp_list_head lh;

Linked list is created by embedding one of the list head strucures into a user structure.

The pointers to the list are managed in the list structures.

Utility macros
#define gp_list_entry(ptr, structure, member) ...

#define gp_list_foreach(list, entry) ...

#define gp_dlist_rev_foreach(list, entry) ...

/* Example macro usage */
void func(...)
        gp_list list = {};
        gp_list_head *i;

        gp_list_foreach(&list, i) {
                struct user_struct *u = gp_list_entry(i, struct user_struct, lh);
                /* process the entry here */

These three utility macros implements looping over the list members.

Functions to push elements to the list
void gp_list_push_head(gp_list *list, gp_list_head *entry);
void gp_list_push_tail(gp_list *list, gp_list_head *entry);

void gp_dlist_push_head(gp_dlist *list, gp_dlist_head *entry);
void gp_dlist_push_tail(gp_dlist *list, gp_dlist_head *entry);

/* Example usage */
void func(gp_list *list)
        struct user_struct *u = malloc(...);


        gp_list_push_tail(list, &(u->lh));

These functions push elements to the head/tail of the list and update the list counter.

Functions to remove elements from the list
gp_list_head *gp_list_pop_head(gp_list *list);

gp_dlist_head *gp_dlist_pop_head(gp_dlist *list);
gp_dlist_head *gp_dlist_pop_tail(gp_dlist *list);
void gp_dlist_rem(gp_dlist *list, gp_dlist_head *entry);

/* Example usage */
struct user_struct *func(gp_list *list)
        gp_list_head *ret = gp_list_pop_head(list);

        if (!ret)
                return NULL;

        return gp_list_entry(ret, sturct user_struct, lh);

These functions remove elements from list and update the list counter.

List sort
void gp_list_sort(gp_list *list, int (*cmp)(const void *, const void *));

void gp_dlist_sort(gp_list *list, int (*cmp)(const void *, const void *));

/* Example usage */
static int cmp(const void *a, const void *b)
        struct user_entry *ua = gp_list_entry(a, struct user_entry, lh);
        struct user_entry *ub = gp_list_entry(b, struct user_entry, lh);

        return ua->int_val - ub->int_val;

        gp_list_sort(list, cmp);

Sorts a linked list, the sorting function is implemented as a merge sort that runs in O(n * log(n)).