/*
 *   kmap - (Linux) kernel map implementation
 *
 *   Copyright (c) 2011 Guillermo Ramos <0xwille@gmail.com>
 *
 * This file is part of kmap
 *
 * kmap is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * kmap is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with kmap.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/errno.h>
#include <linux/list.h>
#include <linux/slab.h>
#include "kmap.h"

/*
 * Returns the node with the value passed, or NULL in case it does not exist
 */
static inline struct kmap *kmap_search(struct kmap *head, int value)
{
    struct list_head *list;
    struct kmap *node;

    list_for_each(list, &head->l) {
        node = list_entry(list, struct kmap, l);
        if (node->value == value)
            return node;
    }

    return NULL;
}

/*
 * Prints in klog a representation of all the nodes in the map
 */
void kmap_display(struct kmap *head)
{
    struct kmap *node;
    struct list_head *list;

    printk(KERN_ALERT "Displaying...");
    list_for_each(list, &head->l) {
        node = list_entry(list, struct kmap, l);
        printk(KERN_ALERT "  %p: v=%d d=%s\n",
               node, node->value, (char*)node->data);
    }
}

/*
 * Creates and returns a new head node
 */
inline struct kmap *kmap_create(void)
{
    struct kmap *head;

    head = kmalloc(sizeof(struct kmap), GFP_KERNEL);
    if (unlikely(!head))
        return NULL;

    INIT_LIST_HEAD(&head->l);

    return head;
}

/*
 * Deletes the map and frees the memory used by its nodes
 */
void kmap_destroy(struct kmap *head)
{
    struct kmap *node;
    struct list_head *list = head->l.next;

    while (list != &head->l) {
        node = list_entry(list, struct kmap, l);
        list = list->next;
        kfree(node);
    }

    kfree(head);
}

/*
 * Creates a new node with the given value and data, and adds it to the map head
 */
int kmap_insert(struct kmap *head, int value, void *data)
{
    struct kmap *new;

    // Key already exists
    if (kmap_search(head, value))
        return -EINVAL;

    new = kmap_create();
    if (unlikely(!new))
        return -ENOMEM;

    new->value = value;
    new->data = data;
    list_add_tail(&new->l, &head->l);

    return 0;
}

/*
 * Removes from the map the node with the given value.
 */
int kmap_delete(struct kmap *head, int value)
{
    struct kmap *node = kmap_search(head, value);

    if (node) {
        list_del(&node->l);
        kfree(node);
        return 0;
    } else {
        return -EINVAL;
    }
}

/*
 * Returns the data mapped to the given value, or NULL if that value has no data
 * associated to it
 */
void *kmap_get(struct kmap *head, int value)
{
    struct kmap *node = kmap_search(head, value);

    if (node)
        return node->data;
    else
        return NULL;
}

/*
 * Associates the given value with new data, if the value was already in the map
 */
void kmap_set(struct kmap *head, int value, void *data)
{
    struct kmap *node = kmap_search(head, value);

    if (node)
        node->data = data;
}