Linked List demo 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct slist_node
{
    void *data;
    struct slist_node *next;
};

typedef void (*datafree_t)(void *data);
struct slist
{
    struct slist_node *head;
    datafree_t datafree;
};

typedef void (*node_visit_t)(struct slist_node *node);
typedef int (*datacmp_t)(void *a, void *b);

void slist_walk(struct slist *list, node_visit_t visit)
{
    struct slist_node *node = NULL;
    for (node = list->head; node; node = node->next)
    {
        visit(node);
    }
}

void slist_print_strings(struct slist *list)
{
    slist_walk(list, snode_print_string_data);
}

struct slist_node *slist_node_new(void *data)
{
    struct slist_node *new = malloc(sizeof(*new));
    // printf("slist_node_new() %p\n", new);
    new->data = data;
    new->next = NULL;
    return new;
}
void slist_add_left(struct slist *list, struct slist_node *node)
{
    node->next = list->head;
    list->head = node;
    return;
}

void slist_node_free(struct slist_node *node, datafree_t datafree)
{
    // printf("slist_node_free() %p\n", node);
    if (datafree)
    {
        datafree(node->data);
    }
    free(node);
}

void slist_delete_node(struct slist *list, void *key, datacmp_t compare)
{
    if (list->head)
    {
        if (compare(list->head->data, key) == 0)
        {
            struct slist_node *node = list->head;
            list->head = list->head->next;
            slist_node_free(node, list->datafree);
        }
        else
        {
            struct slist_node *prev = list->head;
            struct slist_node *current = prev->next;
            while (current)
            {
                if (compare(current->data, key) == 0)
                {
                    prev->next = current->next;
                    slist_node_free(current, list->datafree);
                    return;
                }
                prev = current;
                current = current->next;
            }
        }
    }
}

void slist_free(struct slist *list)
{
    struct slist_node *next;
    struct slist_node *current = list->head;

    while (current)
    {
        next = current->next;
        slist_node_free(current, list->datafree);
        current = next;
    }
}

struct slist_node *slist_find_node(struct slist *list, void *key, datacmp_t compare)
{
    struct slist_node *node;
    for (node = list->head; node; node = node->next)
    {
        if (compare(key, node->data) == 0)
        {
            return node;
        }
    }
    return NULL;
}

void snode_print_string_data(struct slist_node *node)
{
    printf("data = %s, \n", node->data);
}

char *console_read_string(void)
{
    char *str = malloc(100);
    printf("malloc() str = %p\n", str);
    scanf("%100s", str);
    fflush(stdin);
    return str;
}

void free_string(char *str)
{
    printf("free_string() %p\n", str);
    free(str);
}

int main(void)
{
    fflush(stdin);
    struct slist list = {0};
    list.datafree = free_string;

    for (int i = 0; i < 5; i++)
    {
        slist_add_left(&list, slist_node_new(console_read_string()));
    }

    struct slist_node *three = slist_find_node(&list, "three", strcmp);
    if (three)
    {
        printf("Found!\n");
    }
    else
    {
        printf("Not found!\n");
    }

    printf("Deleting 'one'!\n");
    slist_delete_node(&list, "one", strcmp);
    slist_print_strings(&list);

    printf("Deleting 'three'!\n");
    slist_delete_node(&list, "three", strcmp);
    slist_print_strings(&list);

    slist_free(&list);
    return 0;
}