path: root/src/plist.h

/*
 * 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/
 *
 *
 * Priority list.
 *
 * This container acts as a doubly-linked list sorted by priority in
 * ascending order. All operations behave as with a regular linked list
 * except insertion, which is O(k), k being the number of priorities
 * among the entries.
 */

#ifndef PLIST_H
#define PLIST_H

#include <stdbool.h>

#include "list.h"
#include "macros.h"

/*
 * Priority list.
 *
 * The list member is used as the underlying regular linked list and
 * contains all entries, sorted by priority in ascending order. The
 * prio_list member contains exactly one entry for each priority
 * present, also sorted by priority in ascending order. An entry
 * on prio_list is the first entry in list for that priority.
 * Here is a representation of a possible priority list :
 *
 *      list--|1|--|3|--|3|--|3|--|4|--|6|--|6|--|8|
 *            | |  | |            | |  | |       |
 * prio_list--+ +--+ +------------+ +--+ +-------+
 *
 */
struct plist {
    struct list list;
    struct list prio_list;
};

/*
 * Priority list node.
 */
struct plist_node {
    unsigned int priority;
    struct list node;
    struct list prio_node;
};

/*
 * Static priority list initializer.
 */
#define PLIST_INITIALIZER(plist) \
    { LIST_INITIALIZER((plist).list), LIST_INITIALIZER((plist).prio_list) }

/*
 * Initialize a priority list.
 */
static inline void
plist_init(struct plist *plist)
{
    list_init(&plist->list);
    list_init(&plist->prio_list);
}

/*
 * Initialize a priority list node.
 */
static inline void
plist_node_init(struct plist_node *pnode, unsigned int priority)
{
    pnode->priority = priority;
    list_node_init(&pnode->node);
    list_node_init(&pnode->prio_node);
}

/*
 * Return the priority associated with a node.
 */
static inline unsigned int
plist_node_priority(const struct plist_node *pnode)
{
    return pnode->priority;
}

/*
 * Update the priority of an already initialized node.
 */
static inline void
plist_node_set_priority(struct plist_node *pnode, unsigned int priority)
{
    pnode->priority = priority;
}

/*
 * Return true if pnode is in no priority lists.
 */
static inline bool
plist_node_unlinked(const struct plist_node *pnode)
{
    return list_node_unlinked(&pnode->node);
}

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

/*
 * Return the first node of a priority list.
 */
static inline struct plist_node *
plist_first(const struct plist *plist)
{
    return list_first_entry(&plist->list, struct plist_node, node);
}

/*
 * Return the last node of a priority list.
 */
static inline struct plist_node *
plist_last(const struct plist *plist)
{
    return list_last_entry(&plist->list, struct plist_node, node);
}

/*
 * Return the node next to the given node.
 */
static inline struct plist_node *
plist_next(const struct plist_node *pnode)
{
    return (struct plist_node *)list_next_entry(pnode, node);
}

/*
 * Return the node previous to the given node.
 */
static inline struct plist_node *
plist_prev(const struct plist_node *pnode)
{
    return (struct plist_node *)list_prev_entry(pnode, node);
}

/*
 * Get the first entry of a priority list.
 */
#define plist_first_entry(plist, type, member) \
    plist_entry(plist_first(plist), type, member)

/*
 * Get the last entry of a priority list.
 */
#define plist_last_entry(plist, type, member) \
    plist_entry(plist_last(plist), type, member)

/*
 * Get the entry next to the given entry.
 */
#define plist_next_entry(entry, member) \
    plist_entry(plist_next(&(entry)->member), typeof(*(entry)), member)

/*
 * Get the entry previous to the given entry.
 */
#define plist_prev_entry(entry, member) \
    plist_entry(plist_prev(&(entry)->member), typeof(*(entry)), member)

/*
 * Return true if node is after the last or before the first node of
 * a priority list.
 */
static inline bool
plist_end(const struct plist *plist, const struct plist_node *pnode)
{
    return list_end(&plist->list, &pnode->node);
}

/*
 * Return true if plist is empty.
 */
static inline bool
plist_empty(const struct plist *plist)
{
    return list_empty(&plist->list);
}

/*
 * Return true if plist contains exactly one node.
 */
static inline bool
plist_singular(const struct plist *plist)
{
    return list_singular(&plist->list);
}

/*
 * Add a node to a priority list.
 *
 * If the priority list already contains nodes with the same priority
 * as the given node, it is inserted before them.
 *
 * The node must be initialized before calling this function.
 */
void plist_add(struct plist *plist, struct plist_node *pnode);

/*
 * Remove a node from a priority list.
 *
 * After completion, the node is stale.
 */
void plist_remove(struct plist *plist, struct plist_node *pnode);

/*
 * Forge a loop to process all nodes of a priority list.
 *
 * The node must not be altered during the loop.
 */
#define plist_for_each(plist, pnode)    \
for (pnode = plist_first(plist);        \
     !plist_end(plist, pnode);          \
     pnode = plist_next(pnode))

/*
 * Forge a loop to process all nodes of a priority list.
 */
#define plist_for_each_safe(plist, pnode, tmp)              \
for (pnode = plist_first(plist), tmp = plist_next(pnode);   \
     !plist_end(plist, pnode);                              \
     pnode = tmp, tmp = plist_next(pnode))

/*
 * Version of plist_for_each() that processes nodes backward.
 */
#define plist_for_each_reverse(plist, pnode)    \
for (pnode = plist_last(plist);                 \
     !plist_end(plist, pnode);                  \
     pnode = plist_prev(pnode))

/*
 * Version of plist_for_each_safe() that processes nodes backward.
 */
#define plist_for_each_reverse_safe(plist, pnode, tmp)      \
for (pnode = plist_last(plist), tmp = plist_prev(pnode);    \
     !plist_end(plist, pnode);                              \
     pnode = tmp, tmp = plist_prev(pnode))

/*
 * Forge a loop to process all entries of a priority list.
 *
 * The entry node must not be altered during the loop.
 */
#define plist_for_each_entry(plist, entry, member) \
    list_for_each_entry(&(plist)->list, entry, member.node)

/*
 * Forge a loop to process all entries of a priority list.
 */
#define plist_for_each_entry_safe(plist, entry, tmp, member) \
    list_for_each_entry_safe(&(plist)->list, entry, tmp, member.node)

/*
 * Version of plist_for_each_entry() that processes entries backward.
 */
#define plist_for_each_entry_reverse(plist, entry, member) \
    list_for_each_entry_reverse(&(plist)->list, entry, member.node)

/*
 * Version of plist_for_each_entry_safe() that processes entries backward.
 */
#define plist_for_each_entry_reverse_safe(plist, entry, tmp, member) \
    list_for_each_entry_reverse_safe(&(plist)->list, entry, tmp, member.node)

#endif /* PLIST_H */