list.c

#include <stdio.h>
#include <string.h>
#include "list.h"

void list_init(List *list, void(*destroy)(void *data)){
    list->size = 0;
    list->destroy = destroy;
    list->head = NULL;
    list->tail = NULL;
}

void list_destroy(List *list){
    void *data;

    while(list_size(list) > 0){
        if(list_rem_next(list,NULL,(void **)&data) == 0 && list->destroy != NULL){
            list_destroy(data);
        }
    }
    memset(list,0, sizeof(List));
}

int list_ins_next(List *list, ListElmt *element, const void *data){
    ListElmt *new_element;

    if((new_element = (ListElmt *) malloc(sizeof(ListElmt))) == NULL) return -1;

    new_element->data = (void *) data;
    if(element == NULL){
        if(list_size(list) == 0){
            list->tail = new_element;
        }
        new_element->next = list->head;
        list->head = new_element;
    }else{
        if(element->next == NULL){
            list->tail = new_element;
        }
        new_element->next = element->next;
        element->next = new_element;
    }

    list->size++;
    return 0;
}

int list_rem_next(List *list, ListElmt *element, void **data){
    ListElmt *old_element;

    if(list_size(list) == 0) return -1;

    if(element == NULL){
        *data = list->head->data;
        old_element = list->head;
        list->head = list->head->next;

        if(list_size(list) == 1){
            list->tail = NULL;
        }
    }else{
        if(element->next == NULL) return -1;

        *data = element->next->data;
        old_element = element->next;
        element->next = element->next->next;

        if(element->next == NULL){
            list->tail = element;
        }
    }

    free(old_element);
    list->size--;
    return 0;
}