alist.c

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#include <stddef.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

#include "alist.h"

struct alist {
        struct alist *next;
        struct alist *prev;
};

struct alist *alist_append(struct alist *list, struct alist *new)
{
        new->next = NULL;

        if (!list) {
                new->prev = new;

                list = new;
        } else {
                new->prev = list->prev;
                new->prev->next = new;
                list->prev = new;
        }

        return list;
}

struct alist *alist_prepend(struct alist *list, struct alist *new)
{
        if (!list) {
                new->prev = new;
                new->next = NULL;
        } else {
                if (list->prev->next) {
                        list->prev->next = new;
                }

                new->prev = list->prev;
                new->next = list;

                list->prev = new;
        }

        return new;
}

struct alist *alist_remove(struct alist *list, struct alist *l)
{
        if (!list || !l) {
                return NULL;
        }

        if (l == list) {
                list = l->next;
        } else {
                l->prev->next = l->next;
        }

        if (l->next) {
                l->next->prev = l->prev;
        }
        else if (list) {
                list->prev = l->prev;
        }

        return list;
}

struct alist *alist_next(struct alist *l)
{
        return l ? l->next : NULL;
}

struct alist *alist_prev(struct alist *l)
{
        return l ? l->prev : NULL;
}

int alist_count(struct alist *l)
{
        register int i;
        struct alist *n;

        i = 0;
        alist_foreach(l, n) {
                i++;
        }

        return i;
}

struct alist *alist_nth(struct alist *l, int nth)
{
        register int i;
        struct alist *n;

        i = 0;
        for (n = l; n; n = n->next) {
                if (i == nth) {
                        return n;
                }
                i++;
        }

        return NULL;
}

/* End of a file */