/*
 * Copyright (c) 2017 Richard Braun.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Upstream site with license notes :
 * http://git.sceen.net/rbraun/librbraun.git/
 *
 *
 * Singly-linked list.
 */

#ifndef SLIST_H
#define SLIST_H

#include <stdbool.h>
#include <stddef.h>

#include "macros.h"

/*
 * List node.
 */
struct slist_node {
    struct slist_node *next;
};

/*
 * List head.
 */
struct slist {
    struct slist_node *first;
    struct slist_node *last;
};

/*
 * Static list initializer.
 */
#define SLIST_INITIALIZER(list) { NULL, NULL }

/*
 * Initialize a list.
 */
static inline void
slist_init(struct slist *list)
{
    list->first = NULL;
    list->last = NULL;
}

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

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

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

/*
 * Return true if node is invalid and denotes one of the ends of the list.
 */
static inline bool
slist_end(const struct slist_node *node)
{
    return node == NULL;
}

/*
 * Return true if list is empty.
 */
static inline bool
slist_empty(const struct slist *list)
{
    return list->first == NULL;
}

/*
 * Return true if list contains exactly one node.
 */
static inline bool
slist_singular(const struct slist *list)
{
    return !slist_empty(list) && (list->first == list->last);
}

/*
 * Append the nodes of list2 at the end of list1.
 *
 * After completion, list2 is stale.
 */
static inline void
slist_concat(struct slist *list1, const struct slist *list2)
{
    if (slist_empty(list2)) {
        return;
    }

    if (slist_empty(list1)) {
        list1->first = list2->first;
    } else {
        list1->last->next = list2->first;
    }

    list1->last = list2->last;
}

/*
 * Set the new head of a list.
 *
 * This function is an optimized version of :
 * list_init(&new_list);
 * list_concat(&new_list, &old_list);
 */
static inline void
slist_set_head(struct slist *new_head, const struct slist *old_head)
{
    *new_head = *old_head;
}

/*
 * Insert a node at the head of a list.
 */
static inline void
slist_insert_head(struct slist *list, struct slist_node *node)
{
    if (slist_empty(list)) {
        list->last = node;
    }

    node->next = list->first;
    list->first = node;
}

/*
 * Insert a node at the tail of a list.
 */
static inline void
slist_insert_tail(struct slist *list, struct slist_node *node)
{
    node->next = NULL;

    if (slist_empty(list)) {
        list->first = node;
    } else {
        list->last->next = node;
    }

    list->last = node;
}

/*
 * Insert a node after another node.
 *
 * The prev node must be valid.
 */
static inline void
slist_insert_after(struct slist *list, struct slist_node *node,
                   struct slist_node *prev)
{
    node->next = prev->next;
    prev->next = node;

    if (list->last == prev) {
        list->last = node;
    }
}

/*
 * Remove a node from a list.
 *
 * The prev argument must point to the node immediately preceding the target
 * node. It may safely denote the end of the given list (NULL), in which case
 * the first node is removed.
 */
static inline void
slist_remove(struct slist *list, struct slist_node *prev)
{
    struct slist_node *node;

    if (slist_end(prev)) {
        node = list->first;
        list->first = node->next;

        if (list->last == node) {
            list->last = NULL;
        }
    } else {
        node = prev->next;
        prev->next = node->next;

        if (list->last == node) {
            list->last = prev;
        }
    }
}

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

/*
 * Get the first entry of a list.
 */
#define slist_first_entry(list, type, member)                           \
MACRO_BEGIN                                                             \
    struct slist_node *first_;                                          \
                                                                        \
    first_ = (list)->first;                                             \
    slist_end(first_) ? NULL : slist_entry(first_, type, member);       \
MACRO_END

/*
 * Get the last entry of a list.
 */
#define slist_last_entry(list, type, member)                            \
MACRO_BEGIN                                                             \
    struct slist_node *last_;                                           \
                                                                        \
    last_ = (list)->last;                                               \
    slist_end(last_) ? NULL : slist_entry(last_, type, member);         \
MACRO_END

/*
 * Get the entry next to the given entry.
 */
#define slist_next_entry(entry, member)                                 \
MACRO_BEGIN                                                             \
    struct slist_node *next_;                                           \
                                                                        \
    next_ = (entry)->member.next;                                       \
    slist_end(next_)                                                    \
        ? NULL                                                          \
        : slist_entry(next_, typeof(*entry), member);                   \
MACRO_END

/*
 * Forge a loop to process all nodes of a list.
 *
 * The node must not be altered during the loop.
 */
#define slist_for_each(list, node)  \
for (node = slist_first(list);      \
     !slist_end(node);              \
     node = slist_next(node))

/*
 * Forge a loop to process all nodes of a list.
 */
#define slist_for_each_safe(list, node, tmp)            \
for (node = slist_first(list),                          \
     tmp = slist_end(node) ? NULL : slist_next(node);   \
     !slist_end(node);                                  \
     node = tmp,                                        \
     tmp = slist_end(node) ? NULL : slist_next(node))

/*
 * Forge a loop to process all entries of a list.
 *
 * The entry node must not be altered during the loop.
 */
#define slist_for_each_entry(list, entry, member)               \
for (entry = slist_first_entry(list, typeof(*entry), member);   \
     entry != NULL;                                             \
     entry = slist_next_entry(entry, member))

/*
 * Forge a loop to process all entries of a list.
 */
#define slist_for_each_entry_safe(list, entry, tmp, member)             \
for (entry = slist_first_entry(list, typeof(*entry), member),           \
     tmp = (entry == NULL) ? NULL : slist_next_entry(entry, member);    \
     entry != NULL;                                                     \
     entry = tmp,                                                       \
     tmp = (entry == NULL) ? NULL : slist_next_entry(entry, member))    \

/*
 * Lockless variants
 *
 * The slist_end() function may be used from read-side critical sections.
 */

/*
 * These macros can be replaced by actual functions in an environment
 * that provides lockless synchronization such as RCU.
 */
#define rcu_store_ptr(ptr, value)    ((ptr) = (value))
#define rcu_load_ptr(ptr)            (ptr)

/*
 * Return the first node of a list.
 */
static inline struct slist_node *
slist_rcu_first(const struct slist *list)
{
    return rcu_load_ptr(list->first);
}

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

/*
 * Insert a node at the head of a list.
 */
static inline void
slist_rcu_insert_head(struct slist *list, struct slist_node *node)
{
    if (slist_empty(list)) {
        list->last = node;
    }

    node->next = list->first;
    rcu_store_ptr(list->first, node);
}

/*
 * Insert a node at the tail of a list.
 */
static inline void
slist_rcu_insert_tail(struct slist *list, struct slist_node *node)
{
    node->next = NULL;

    if (slist_empty(list)) {
        rcu_store_ptr(list->first, node);
    } else {
        rcu_store_ptr(list->last->next, node);
    }

    list->last = node;
}

/*
 * Insert a node after another node.
 *
 * The prev node must be valid.
 */
static inline void
slist_rcu_insert_after(struct slist *list, struct slist_node *node,
                          struct slist_node *prev)
{
    node->next = prev->next;
    rcu_store_ptr(prev->next, node);

    if (list->last == prev) {
        list->last = node;
    }
}

/*
 * Remove a node from a list.
 *
 * The prev argument must point to the node immediately preceding the target
 * node. It may safely denote the end of the given list, in which case the
 * first node is removed.
 */
static inline void
slist_rcu_remove(struct slist *list, struct slist_node *prev)
{
    struct slist_node *node;

    if (slist_end(prev)) {
        node = list->first;
        rcu_store_ptr(list->first, node->next);

        if (list->last == node) {
            list->last = NULL;
        }
    } else {
        node = prev->next;
        rcu_store_ptr(prev->next, node->next);

        if (list->last == node) {
            list->last = prev;
        }
    }
}

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

/*
 * Get the first entry of a list.
 */
#define slist_rcu_first_entry(list, type, member)                       \
MACRO_BEGIN                                                             \
    struct slist_node *first_;                                          \
                                                                        \
    first_ = slist_rcu_first(list);                                     \
    slist_end(first_) ? NULL : slist_entry(first_, type, member);       \
MACRO_END

/*
 * Get the entry next to the given entry.
 */
#define slist_rcu_next_entry(entry, member)                             \
MACRO_BEGIN                                                             \
    struct slist_node *next_;                                           \
                                                                        \
    next_ = slist_rcu_next(&entry->member);                             \
    slist_end(next_)                                                    \
        ? NULL                                                          \
        : slist_entry(next_, typeof(*entry), member);                   \
MACRO_END

/*
 * Forge a loop to process all nodes of a list.
 */
#define slist_rcu_for_each(list, node)      \
for (node = slist_rcu_first(list);          \
     !slist_end(node);                      \
     node = slist_rcu_next(node))

/*
 * Forge a loop to process all entries of a list.
 */
#define slist_rcu_for_each_entry(list, entry, member)                   \
for (entry = slist_rcu_first_entry(list, typeof(*entry), member);       \
     entry != NULL;                                                     \
     entry = slist_rcu_next_entry(entry, member))

#endif /* SLIST_H */