/*
 * Copyright (c) 2009, 2010 Richard Braun.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * Simple doubly-linked list.
 */

#ifndef _KERN_LIST_H
#define _KERN_LIST_H

#include <stddef.h>
#include <sys/types.h>

#define structof(ptr, type, member) \
    ((type *)((char *)ptr - offsetof(type, member)))

/*
 * Structure used as both head and node.
 *
 * This implementation relies on using the same type for both heads and nodes.
 *
 * It is recommended to encode the use of struct list variables in their names,
 * e.g. struct list free_list or struct list free_objects is a good hint for a
 * list of free objects. A declaration like struct list free_node clearly
 * indicates it is used as part of a node in the free list.
 */
struct list {
    struct list *prev;
    struct list *next;
};

/*
 * Static list initializer.
 */
#define LIST_INITIALIZER(list) { &(list), &(list) }

/*
 * Initialize a list.
 */
static inline void list_init(struct list *list)
{
    list->prev = list;
    list->next = list;
}

/*
 * Initialize a list node.
 *
 * An entry is in no list when its node members point to NULL.
 */
static inline void list_node_init(struct list *node)
{
    node->prev = NULL;
    node->next = NULL;
}

/*
 * Return true if node is in no list.
 */
static inline int list_node_unlinked(const struct list *node)
{
    return node->prev == NULL;
}

/*
 * Macro that evaluates to the address of the structure containing the
 * given node based on the given type and member.
 */
#define list_entry(node, type, member) structof(node, type, member)

/*
 * Return the first node of a list.
 */
static inline struct list * list_first(const struct list *list)
{
    return list->next;
}

/*
 * Return the last node of a list.
 */
static inline struct list * list_last(const struct list *list)
{
    return list->prev;
}

/*
 * Return the node next to the given node.
 */
static inline struct list * list_next(const struct list *node)
{
    return node->next;
}

/*
 * Return the node previous to the given node.
 */
static inline struct list * list_prev(const struct list *node)
{
    return node->prev;
}

/*
 * Get the first entry of a list.
 */
#define list_first_entry(list, type, member) \
    list_entry(list_first(list), type, member)

/*
 * Get the last entry of a list.
 */
#define list_last_entry(list, type, member) \
    list_entry(list_last(list), type, member)

/*
 * Return true if node is after the last or before the first node of the list.
 */
static inline int list_end(const struct list *list, const struct list *node)
{
    return list == node;
}

/*
 * Return true if list is empty.
 */
static inline int list_empty(const struct list *list)
{
    return list == list->next;
}

/*
 * Return true if list contains exactly one node.
 */
static inline int list_singular(const struct list *list)
{
    return (list != list->next) && (list->next == list->prev);
}

/*
 * Split list2 by moving its nodes up to (but not including) the given
 * node into list1 (which can be in a stale state).
 *
 * If list2 is empty, or node is list2 or list2->next, nothing is done.
 */
static inline void list_split(struct list *list1, struct list *list2,
                              struct list *node)
{
    if (list_empty(list2) || (list2->next == node) || list_end(list2, node))
        return;

    list1->next = list2->next;
    list1->next->prev = list1;

    list1->prev = node->prev;
    node->prev->next = list1;

    list2->next = node;
    node->prev = list2;
}

/*
 * Append the nodes of list2 at the end of list1.
 *
 * After completion, list2 is stale.
 */
static inline void list_concat(struct list *list1, const struct list *list2)
{
    struct list *last1, *first2, *last2;

    if (list_empty(list2))
        return;

    last1 = list1->prev;
    first2 = list2->next;
    last2 = list2->prev;

    last1->next = first2;
    first2->prev = last1;

    last2->next = list1;
    list1->prev = last2;
}

/*
 * Set the new head of a list.
 *
 * This function is an optimized version of :
 * list_init(&new_list);
 * list_concat(&new_list, &old_list);
 *
 * After completion, old_head is stale.
 */
static inline void list_set_head(struct list *new_head,
                                 const struct list *old_head)
{
    if (list_empty(old_head)) {
        list_init(new_head);
        return;
    }

    *new_head = *old_head;
    new_head->next->prev = new_head;
    new_head->prev->next = new_head;
}

/*
 * Add a node between two nodes.
 */
static inline void list_add(struct list *prev, struct list *next,
                            struct list *node)
{
    next->prev = node;
    node->next = next;

    prev->next = node;
    node->prev = prev;
}

/*
 * Insert a node at the head of a list.
 */
static inline void list_insert(struct list *list, struct list *node)
{
    list_add(list, list->next, node);
}

/*
 * Insert a node at the tail of a list.
 */
static inline void list_insert_tail(struct list *list, struct list *node)
{
    list_add(list->prev, list, node);
}

/*
 * Insert a node before another node.
 */
static inline void list_insert_before(struct list *next, struct list *node)
{
    list_add(next->prev, next, node);
}

/*
 * Insert a node after another node.
 */
static inline void list_insert_after(struct list *prev, struct list *node)
{
    list_add(prev, prev->next, node);
}

/*
 * Remove a node from a list.
 *
 * After completion, the node is stale.
 */
static inline void list_remove(struct list *node)
{
    node->prev->next = node->next;
    node->next->prev = node->prev;
}

/*
 * Forge a loop to process all nodes of a list.
 *
 * The node must not be altered during the loop.
 */
#define list_for_each(list, node)   \
for (node = list_first(list);       \
     !list_end(list, node);         \
     node = list_next(node))

/*
 * Forge a loop to process all nodes of a list.
 */
#define list_for_each_safe(list, node, tmp)             \
for (node = list_first(list), tmp = list_next(node);    \
     !list_end(list, node);                             \
     node = tmp, tmp = list_next(node))

/*
 * Version of list_for_each() that processes nodes backward.
 */
#define list_for_each_reverse(list, node)   \
for (node = list_last(list);                \
     !list_end(list, node);                 \
     node = list_prev(node))

/*
 * Version of list_for_each_safe() that processes nodes backward.
 */
#define list_for_each_reverse_safe(list, node, tmp) \
for (node = list_last(list), tmp = list_prev(node); \
     !list_end(list, node);                         \
     node = tmp, tmp = list_prev(node))

/*
 * Forge a loop to process all entries of a list.
 *
 * The entry node must not be altered during the loop.
 */
#define list_for_each_entry(list, entry, member)                    \
for (entry = list_entry(list_first(list), typeof(*entry), member);  \
     !list_end(list, &entry->member);                               \
     entry = list_entry(list_next(&entry->member), typeof(*entry),  \
                        member))

/*
 * Forge a loop to process all entries of a list.
 */
#define list_for_each_entry_safe(list, entry, tmp, member)          \
for (entry = list_entry(list_first(list), typeof(*entry), member),  \
       tmp = list_entry(list_next(&entry->member), typeof(*entry),  \
                        member);                                    \
     !list_end(list, &entry->member);                               \
     entry = tmp, tmp = list_entry(list_next(&entry->member),       \
                                   typeof(*entry), member))

/*
 * Version of list_for_each_entry() that processes entries backward.
 */
#define list_for_each_entry_reverse(list, entry, member)            \
for (entry = list_entry(list_last(list), typeof(*entry), member);   \
     !list_end(list, &entry->member);                               \
     entry = list_entry(list_prev(&entry->member), typeof(*entry),  \
                        member))

/*
 * Version of list_for_each_entry_safe() that processes entries backward.
 */
#define list_for_each_entry_reverse_safe(list, entry, tmp, member)  \
for (entry = list_entry(list_last(list), typeof(*entry), member),   \
       tmp = list_entry(list_prev(&entry->member), typeof(*entry),  \
                        member);                                    \
     !list_end(list, &entry->member);                               \
     entry = tmp, tmp = list_entry(list_prev(&entry->member),       \
                                   typeof(*entry), member))

#endif /* _KERN_LIST_H */
