list.c

#include "list.h"

void list_init(list_t *list) {
    list->head = NULL;
    list->tail = NULL;
}

void list_push_front(list_t *list, link_t *link) {
    if (list->head) {
        list->head->prev = link;
        link->prev = NULL;
        link->next = list->head;
        list->head = link;
    } else {
        list->head = link;
        list->tail = link;
        link->next = NULL;
        link->prev = NULL;
    }
}

void list_push_back(list_t *list, link_t *link) {
    if (list->tail) {
        list->tail->next = link;
        link->prev = list->tail;
        link->next = NULL;
        list->tail = link;
    } else {
        list->head = link;
        list->tail = link;
        link->next = NULL;
        link->prev = NULL;
    }
}

void list_insert_after(list_t *list, link_t *after, link_t *link) {
    link->next = after->next;
    link->prev = after;
    if (after->next) after->next->prev = link;
    else list->tail = link;
    after->next = link;
}

void list_insert_before(list_t *list, link_t *before, link_t *link) {
    link->prev = before->prev;
    link->next = before;
    if (before->prev) before->prev->next = link;
    else list->head = link;
    before->prev = link;
}

link_t *list_pop_front(list_t *list) {
    link_t *link = list->head;
    if (!link) return NULL;
    if (link->next) link->next->prev = link->prev;
    if (link->prev) link->prev->next = link->next;
    if (list->head == link) list->head = link->next;
    if (list->tail == link) list->tail = link->prev;
    return link;
}

link_t *list_pop_back(list_t *list) {
    link_t *link = list->tail;
    if (!link) return NULL;
    if (link->next) link->next->prev = link->prev;
    if (link->prev) link->prev->next = link->next;
    if (list->head == link) list->head = link->next;
    if (list->tail == link) list->tail = link->prev;
    return link;
}

void list_remove(list_t *list, link_t *link) {
    if (!link) return;
    if (link->next) link->next->prev = link->prev;
    if (link->prev) link->prev->next = link->next;
    if (list->head == link) list->head = link->next;
    if (list->tail == link) list->tail = link->prev;
}

link_t *list_head(const list_t *list) {
    return list->head;
}

link_t *list_tail(const list_t *list) {
    return list->tail;
}

link_t *list_next(const link_t *link) {
    return link->next;
}

link_t *list_prev(const link_t *link) {
    return link->prev;
}