helper/list: add list_for_each_entry_direction()

[openocd.git] / src / helper / list.h

/* SPDX-License-Identifier: GPL-2.0-only */

/*
 * The content of this file is mainly copied/inspired from Linux kernel
 * code in include/linux/list.h, include/linux/types.h
 * Last aligned with kernel v5.12:
 * - skip the functions hlist_unhashed_lockless() and __list_del_clearprev()
 *   that are relevant only in kernel;
 * - Remove non-standard GCC extension "omitted conditional operand" from
 *   list_prepare_entry;
 * - expand READ_ONCE, WRITE_ONCE, smp_load_acquire, smp_store_release;
 * - make comments compatible with doxygen.
 *
 * There is an example of using this file in contrib/list_example.c.
 */

#ifndef OPENOCD_HELPER_LIST_H
#define OPENOCD_HELPER_LIST_H

/* begin local changes */
#include <helper/types.h>

#define LIST_POISON1 NULL
#define LIST_POISON2 NULL

struct list_head {
        struct list_head *next, *prev;
};

struct hlist_head {
        struct hlist_node *first;
};

struct hlist_node {
        struct hlist_node *next, **pprev;
};
/* end local changes */

/*
 * Circular doubly linked list implementation.
 *
 * Some of the internal functions ("__xxx") are useful when
 * manipulating whole lists rather than single entries, as
 * sometimes we already know the next/prev entries and we can
 * generate better code by using them directly rather than
 * using the generic single-entry routines.
 */

#define LIST_HEAD_INIT(name) { &(name), &(name) }

#define LIST_HEAD(name) \
        struct list_head name = LIST_HEAD_INIT(name)

/**
 * INIT_LIST_HEAD - Initialize a list_head structure
 * @param list list_head structure to be initialized.
 *
 * Initializes the list_head to point to itself.  If it is a list header,
 * the result is an empty list.
 */
static inline void INIT_LIST_HEAD(struct list_head *list)
{
        list->next = list;
        list->prev = list;
}

#ifdef CONFIG_DEBUG_LIST
extern bool __list_add_valid(struct list_head *new,
                              struct list_head *prev,
                              struct list_head *next);
extern bool __list_del_entry_valid(struct list_head *entry);
#else
static inline bool __list_add_valid(struct list_head *new,
                                struct list_head *prev,
                                struct list_head *next)
{
        return true;
}
static inline bool __list_del_entry_valid(struct list_head *entry)
{
        return true;
}
#endif

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_add(struct list_head *new,
                              struct list_head *prev,
                              struct list_head *next)
{
        if (!__list_add_valid(new, prev, next))
                return;

        next->prev = new;
        new->next = next;
        new->prev = prev;
        prev->next = new;
}

/**
 * list_add - add a new entry
 * @param new new entry to be added
 * @param head list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static inline void list_add(struct list_head *new, struct list_head *head)
{
        __list_add(new, head, head->next);
}


/**
 * list_add_tail - add a new entry
 * @param new new entry to be added
 * @param head list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
        __list_add(new, head->prev, head);
}

/*
 * Delete a list entry by making the prev/next entries
 * point to each other.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_del(struct list_head *prev, struct list_head *next)
{
        next->prev = prev;
        prev->next = next;
}

/* Ignore kernel __list_del_clearprev() */

static inline void __list_del_entry(struct list_head *entry)
{
        if (!__list_del_entry_valid(entry))
                return;

        __list_del(entry->prev, entry->next);
}

/**
 * list_del - deletes entry from list.
 * @param entry the element to delete from the list.
 * Note: list_empty() on entry does not return true after this, the entry is
 * in an undefined state.
 */
static inline void list_del(struct list_head *entry)
{
        __list_del_entry(entry);
        entry->next = LIST_POISON1;
        entry->prev = LIST_POISON2;
}

/**
 * list_replace - replace old entry by new one
 * @param old the element to be replaced
 * @param new the new element to insert
 *
 * If @a old was empty, it will be overwritten.
 */
static inline void list_replace(struct list_head *old,
                                struct list_head *new)
{
        new->next = old->next;
        new->next->prev = new;
        new->prev = old->prev;
        new->prev->next = new;
}

/**
 * list_replace_init - replace old entry by new one and initialize the old one
 * @param old the element to be replaced
 * @param new the new element to insert
 *
 * If @a old was empty, it will be overwritten.
 */
static inline void list_replace_init(struct list_head *old,
                                     struct list_head *new)
{
        list_replace(old, new);
        INIT_LIST_HEAD(old);
}

/**
 * list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position
 * @param entry1 the location to place entry2
 * @param entry2 the location to place entry1
 */
static inline void list_swap(struct list_head *entry1,
                             struct list_head *entry2)
{
        struct list_head *pos = entry2->prev;

        list_del(entry2);
        list_replace(entry1, entry2);
        if (pos == entry1)
                pos = entry2;
        list_add(entry1, pos);
}

/**
 * list_del_init - deletes entry from list and reinitialize it.
 * @param entry the element to delete from the list.
 */
static inline void list_del_init(struct list_head *entry)
{
        __list_del_entry(entry);
        INIT_LIST_HEAD(entry);
}

/**
 * list_move - delete from one list and add as another's head
 * @param list the entry to move
 * @param head the head that will precede our entry
 */
static inline void list_move(struct list_head *list, struct list_head *head)
{
        __list_del_entry(list);
        list_add(list, head);
}

/**
 * list_move_tail - delete from one list and add as another's tail
 * @param list the entry to move
 * @param head the head that will follow our entry
 */
static inline void list_move_tail(struct list_head *list,
                                  struct list_head *head)
{
        __list_del_entry(list);
        list_add_tail(list, head);
}

/**
 * list_bulk_move_tail - move a subsection of a list to its tail
 * @param head  the head that will follow our entry
 * @param first the first entry to move
 * @param last  the last entry to move, can be the same as first
 *
 * Move all entries between @a first and including @a last before @a head.
 * All three entries must belong to the same linked list.
 */
static inline void list_bulk_move_tail(struct list_head *head,
                                       struct list_head *first,
                                       struct list_head *last)
{
        first->prev->next = last->next;
        last->next->prev = first->prev;

        head->prev->next = first;
        first->prev = head->prev;

        last->next = head;
        head->prev = last;
}

/**
 * list_is_first -- tests whether @a list is the first entry in list @a head
 * @param list the entry to test
 * @param head the head of the list
 */
static inline int list_is_first(const struct list_head *list,
                                        const struct list_head *head)
{
        return list->prev == head;
}

/**
 * list_is_last - tests whether @a list is the last entry in list @a head
 * @param list the entry to test
 * @param head the head of the list
 */
static inline int list_is_last(const struct list_head *list,
                                const struct list_head *head)
{
        return list->next == head;
}

/**
 * list_empty - tests whether a list is empty
 * @param head the list to test.
 */
static inline int list_empty(const struct list_head *head)
{
        return head->next == head;
}

/**
 * list_del_init_careful - deletes entry from list and reinitialize it.
 * @param entry the element to delete from the list.
 *
 * This is the same as list_del_init(), except designed to be used
 * together with list_empty_careful() in a way to guarantee ordering
 * of other memory operations.
 *
 * Any memory operations done before a list_del_init_careful() are
 * guaranteed to be visible after a list_empty_careful() test.
 */
static inline void list_del_init_careful(struct list_head *entry)
{
        __list_del_entry(entry);
        entry->prev = entry;
        entry->next = entry;
}

/**
 * list_empty_careful - tests whether a list is empty and not being modified
 * @param head the list to test
 *
 * Description:
 * tests whether a list is empty _and_ checks that no other CPU might be
 * in the process of modifying either member (next or prev)
 *
 * NOTE: using list_empty_careful() without synchronization
 * can only be safe if the only activity that can happen
 * to the list entry is list_del_init(). Eg. it cannot be used
 * if another CPU could re-list_add() it.
 */
static inline int list_empty_careful(const struct list_head *head)
{
        struct list_head *next = head->next;
        return (next == head) && (next == head->prev);
}

/**
 * list_rotate_left - rotate the list to the left
 * @param head the head of the list
 */
static inline void list_rotate_left(struct list_head *head)
{
        struct list_head *first;

        if (!list_empty(head)) {
                first = head->next;
                list_move_tail(first, head);
        }
}

/**
 * list_rotate_to_front() - Rotate list to specific item.
 * @param list The desired new front of the list.
 * @param head The head of the list.
 *
 * Rotates list so that @a list becomes the new front of the list.
 */
static inline void list_rotate_to_front(struct list_head *list,
                                        struct list_head *head)
{
        /*
         * Deletes the list head from the list denoted by @a head and
         * places it as the tail of @a list, this effectively rotates the
         * list so that @a list is at the front.
         */
        list_move_tail(head, list);
}

/**
 * list_is_singular - tests whether a list has just one entry.
 * @param head the list to test.
 */
static inline int list_is_singular(const struct list_head *head)
{
        return !list_empty(head) && (head->next == head->prev);
}

static inline void __list_cut_position(struct list_head *list,
                struct list_head *head, struct list_head *entry)
{
        struct list_head *new_first = entry->next;
        list->next = head->next;
        list->next->prev = list;
        list->prev = entry;
        entry->next = list;
        head->next = new_first;
        new_first->prev = head;
}

/**
 * list_cut_position - cut a list into two
 * @param list a new list to add all removed entries
 * @param head a list with entries
 * @param entry an entry within head, could be the head itself
 *      and if so we won't cut the list
 *
 * This helper moves the initial part of @a head, up to and
 * including @a entry, from @a head to @a list. You should
 * pass on @a entry an element you know is on @a head. @a list
 * should be an empty list or a list you do not care about
 * losing its data.
 *
 */
static inline void list_cut_position(struct list_head *list,
                struct list_head *head, struct list_head *entry)
{
        if (list_empty(head))
                return;
        if (list_is_singular(head) &&
                (head->next != entry && head != entry))
                return;
        if (entry == head)
                INIT_LIST_HEAD(list);
        else
                __list_cut_position(list, head, entry);
}

/**
 * list_cut_before - cut a list into two, before given entry
 * @param list  a new list to add all removed entries
 * @param head  a list with entries
 * @param entry an entry within head, could be the head itself
 *
 * This helper moves the initial part of @a head, up to but
 * excluding @a entry, from @a head to @a list.  You should pass
 * in @a entry an element you know is on @a head.  @a list should
 * be an empty list or a list you do not care about losing
 * its data.
 * If @a entry == @a head, all entries on @a head are moved to
 * @a list.
 */
static inline void list_cut_before(struct list_head *list,
                                   struct list_head *head,
                                   struct list_head *entry)
{
        if (head->next == entry) {
                INIT_LIST_HEAD(list);
                return;
        }
        list->next = head->next;
        list->next->prev = list;
        list->prev = entry->prev;
        list->prev->next = list;
        head->next = entry;
        entry->prev = head;
}

static inline void __list_splice(const struct list_head *list,
                                 struct list_head *prev,
                                 struct list_head *next)
{
        struct list_head *first = list->next;
        struct list_head *last = list->prev;

        first->prev = prev;
        prev->next = first;

        last->next = next;
        next->prev = last;
}

/**
 * list_splice - join two lists, this is designed for stacks
 * @param list the new list to add.
 * @param head the place to add it in the first list.
 */
static inline void list_splice(const struct list_head *list,
                                struct list_head *head)
{
        if (!list_empty(list))
                __list_splice(list, head, head->next);
}

/**
 * list_splice_tail - join two lists, each list being a queue
 * @param list the new list to add.
 * @param head the place to add it in the first list.
 */
static inline void list_splice_tail(struct list_head *list,
                                struct list_head *head)
{
        if (!list_empty(list))
                __list_splice(list, head->prev, head);
}

/**
 * list_splice_init - join two lists and reinitialise the emptied list.
 * @param list the new list to add.
 * @param head the place to add it in the first list.
 *
 * The list at @a list is reinitialised
 */
static inline void list_splice_init(struct list_head *list,
                                    struct list_head *head)
{
        if (!list_empty(list)) {
                __list_splice(list, head, head->next);
                INIT_LIST_HEAD(list);
        }
}

/**
 * list_splice_tail_init - join two lists and reinitialise the emptied list
 * @param list the new list to add.
 * @param head the place to add it in the first list.
 *
 * Each of the lists is a queue.
 * The list at @a list is reinitialised
 */
static inline void list_splice_tail_init(struct list_head *list,
                                         struct list_head *head)
{
        if (!list_empty(list)) {
                __list_splice(list, head->prev, head);
                INIT_LIST_HEAD(list);
        }
}

/**
 * list_entry - get the struct for this entry
 * @param ptr    the &struct list_head pointer.
 * @param type   the type of the struct this is embedded in.
 * @param member the name of the list_head within the struct.
 */
#define list_entry(ptr, type, member) \
        container_of(ptr, type, member)

/**
 * list_first_entry - get the first element from a list
 * @param ptr    the list head to take the element from.
 * @param type   the type of the struct this is embedded in.
 * @param member the name of the list_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_first_entry(ptr, type, member) \
        list_entry((ptr)->next, type, member)

/**
 * list_last_entry - get the last element from a list
 * @param ptr    the list head to take the element from.
 * @param type   the type of the struct this is embedded in.
 * @param member the name of the list_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_last_entry(ptr, type, member) \
        list_entry((ptr)->prev, type, member)

/**
 * list_first_entry_or_null - get the first element from a list
 * @param ptr    the list head to take the element from.
 * @param type   the type of the struct this is embedded in.
 * @param member the name of the list_head within the struct.
 *
 * Note that if the list is empty, it returns NULL.
 */
#define list_first_entry_or_null(ptr, type, member) ({ \
        struct list_head *head__ = (ptr); \
        struct list_head *pos__ = head__->next; \
        pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
})

/**
 * list_next_entry - get the next element in list
 * @param pos    the type * to cursor
 * @param member the name of the list_head within the struct.
 */
#define list_next_entry(pos, member) \
        list_entry((pos)->member.next, typeof(*(pos)), member)

/**
 * list_prev_entry - get the prev element in list
 * @param pos    the type * to cursor
 * @param member the name of the list_head within the struct.
 */
#define list_prev_entry(pos, member) \
        list_entry((pos)->member.prev, typeof(*(pos)), member)

/**
 * list_for_each        -       iterate over a list
 * @param pos  the &struct list_head to use as a loop cursor.
 * @param head the head for your list.
 */
#define list_for_each(pos, head) \
        for (pos = (head)->next; pos != (head); pos = pos->next)

/**
 * list_for_each_continue - continue iteration over a list
 * @param pos  the &struct list_head to use as a loop cursor.
 * @param head the head for your list.
 *
 * Continue to iterate over a list, continuing after the current position.
 */
#define list_for_each_continue(pos, head) \
        for (pos = pos->next; pos != (head); pos = pos->next)

/**
 * list_for_each_prev   -       iterate over a list backwards
 * @param pos  the &struct list_head to use as a loop cursor.
 * @param head the head for your list.
 */
#define list_for_each_prev(pos, head) \
        for (pos = (head)->prev; pos != (head); pos = pos->prev)

/**
 * list_for_each_safe - iterate over a list safe against removal of list entry
 * @param pos  the &struct list_head to use as a loop cursor.
 * @param n    another &struct list_head to use as temporary storage
 * @param head the head for your list.
 */
#define list_for_each_safe(pos, n, head) \
        for (pos = (head)->next, n = pos->next; pos != (head); \
                pos = n, n = pos->next)

/**
 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
 * @param pos  the &struct list_head to use as a loop cursor.
 * @param n    another &struct list_head to use as temporary storage
 * @param head the head for your list.
 */
#define list_for_each_prev_safe(pos, n, head) \
        for (pos = (head)->prev, n = pos->prev; \
             pos != (head); \
             pos = n, n = pos->prev)

/**
 * list_entry_is_head - test if the entry points to the head of the list
 * @param pos    the type * to cursor
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 */
#define list_entry_is_head(pos, head, member)                           \
        (&pos->member == (head))

/**
 * list_for_each_entry  -       iterate over list of given type
 * @param pos    the type * to use as a loop cursor.
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 */
#define list_for_each_entry(pos, head, member)                          \
        for (pos = list_first_entry(head, typeof(*pos), member);        \
             !list_entry_is_head(pos, head, member);                    \
             pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_reverse - iterate backwards over list of given type.
 * @param pos    the type * to use as a loop cursor.
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member)                  \
        for (pos = list_last_entry(head, typeof(*pos), member);         \
             !list_entry_is_head(pos, head, member);                    \
             pos = list_prev_entry(pos, member))

/**
 * list_for_each_entry_direction - iterate forward/backward over list of given type
 * @param forward the iterate direction, true for forward, false for backward.
 * @param pos     the type * to use as a loop cursor.
 * @param head    the head for your list.
 * @param member  the name of the list_head within the struct.
 */
#define list_for_each_entry_direction(forward, pos, head, member)               \
        for (pos = forward ? list_first_entry(head, typeof(*pos), member)       \
                                           : list_last_entry(head, typeof(*pos), member);       \
                 !list_entry_is_head(pos, head, member);                                                \
                 pos = forward ? list_next_entry(pos, member)                                   \
                                           : list_prev_entry(pos, member))

/**
 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
 * @param pos    the type * to use as a start point
 * @param head   the head of the list
 * @param member the name of the list_head within the struct.
 *
 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
 */
#define list_prepare_entry(pos, head, member) \
        ((pos) ? (pos) : list_entry(head, typeof(*pos), member))

/**
 * list_for_each_entry_continue - continue iteration over list of given type
 * @param pos    the type * to use as a loop cursor.
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 */
#define list_for_each_entry_continue(pos, head, member)         \
        for (pos = list_next_entry(pos, member);                        \
             !list_entry_is_head(pos, head, member);                    \
             pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_continue_reverse - iterate backwards from the given point
 * @param pos    the type * to use as a loop cursor.
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 */
#define list_for_each_entry_continue_reverse(pos, head, member)         \
        for (pos = list_prev_entry(pos, member);                        \
             !list_entry_is_head(pos, head, member);                    \
             pos = list_prev_entry(pos, member))

/**
 * list_for_each_entry_from - iterate over list of given type from the current point
 * @param pos    the type * to use as a loop cursor.
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from(pos, head, member)                     \
        for (; !list_entry_is_head(pos, head, member);                  \
             pos = list_next_entry(pos, member))

/**
 * list_for_each_entry_from_reverse - iterate backwards over list of given type
 *                                    from the current point
 * @param pos    the type * to use as a loop cursor.
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 *
 * Iterate backwards over list of given type, continuing from current position.
 */
#define list_for_each_entry_from_reverse(pos, head, member)             \
        for (; !list_entry_is_head(pos, head, member);                  \
             pos = list_prev_entry(pos, member))

/**
 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @param pos    the type * to use as a loop cursor.
 * @param n      another type * to use as temporary storage
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)                  \
        for (pos = list_first_entry(head, typeof(*pos), member),        \
                n = list_next_entry(pos, member);                       \
             !list_entry_is_head(pos, head, member);                    \
             pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_continue - continue list iteration safe against removal
 * @param pos    the type * to use as a loop cursor.
 * @param n      another type * to use as temporary storage
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing after current point,
 * safe against removal of list entry.
 */
#define list_for_each_entry_safe_continue(pos, n, head, member)         \
        for (pos = list_next_entry(pos, member),                                \
                n = list_next_entry(pos, member);                               \
             !list_entry_is_head(pos, head, member);                            \
             pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
 * @param pos    the type * to use as a loop cursor.
 * @param n      another type * to use as temporary storage
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 *
 * Iterate over list of given type from current point, safe against
 * removal of list entry.
 */
#define list_for_each_entry_safe_from(pos, n, head, member)                     \
        for (n = list_next_entry(pos, member);                                  \
             !list_entry_is_head(pos, head, member);                            \
             pos = n, n = list_next_entry(n, member))

/**
 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
 * @param pos    the type * to use as a loop cursor.
 * @param n      another type * to use as temporary storage
 * @param head   the head for your list.
 * @param member the name of the list_head within the struct.
 *
 * Iterate backwards over list of given type, safe against removal
 * of list entry.
 */
#define list_for_each_entry_safe_reverse(pos, n, head, member)          \
        for (pos = list_last_entry(head, typeof(*pos), member),         \
                n = list_prev_entry(pos, member);                       \
             !list_entry_is_head(pos, head, member);                    \
             pos = n, n = list_prev_entry(n, member))

/**
 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
 * @param pos    the loop cursor used in the list_for_each_entry_safe loop
 * @param n      temporary storage used in list_for_each_entry_safe
 * @param member the name of the list_head within the struct.
 *
 * list_safe_reset_next is not safe to use in general if the list may be
 * modified concurrently (eg. the lock is dropped in the loop body). An
 * exception to this is if the cursor element (pos) is pinned in the list,
 * and list_safe_reset_next is called after re-taking the lock and before
 * completing the current iteration of the loop body.
 */
#define list_safe_reset_next(pos, n, member)                            \
        n = list_next_entry(pos, member)

/*
 * Double linked lists with a single pointer list head.
 * Mostly useful for hash tables where the two pointer list head is
 * too wasteful.
 * You lose the ability to access the tail in O(1).
 */

#define HLIST_HEAD_INIT { .first = NULL }
#define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
static inline void INIT_HLIST_NODE(struct hlist_node *h)
{
        h->next = NULL;
        h->pprev = NULL;
}

/**
 * hlist_unhashed - Has node been removed from list and reinitialized?
 * @param h Node to be checked
 *
 * Not that not all removal functions will leave a node in unhashed
 * state.  For example, hlist_nulls_del_init_rcu() does leave the
 * node in unhashed state, but hlist_nulls_del() does not.
 */
static inline int hlist_unhashed(const struct hlist_node *h)
{
        return !h->pprev;
}

/* Ignore kernel hlist_unhashed_lockless() */

/**
 * hlist_empty - Is the specified hlist_head structure an empty hlist?
 * @param h Structure to check.
 */
static inline int hlist_empty(const struct hlist_head *h)
{
        return !h->first;
}

static inline void __hlist_del(struct hlist_node *n)
{
        struct hlist_node *next = n->next;
        struct hlist_node **pprev = n->pprev;

        *pprev = next;
        if (next)
                next->pprev = pprev;
}

/**
 * hlist_del - Delete the specified hlist_node from its list
 * @param n Node to delete.
 *
 * Note that this function leaves the node in hashed state.  Use
 * hlist_del_init() or similar instead to unhash @a n.
 */
static inline void hlist_del(struct hlist_node *n)
{
        __hlist_del(n);
        n->next = LIST_POISON1;
        n->pprev = LIST_POISON2;
}

/**
 * hlist_del_init - Delete the specified hlist_node from its list and initialize
 * @param n Node to delete.
 *
 * Note that this function leaves the node in unhashed state.
 */
static inline void hlist_del_init(struct hlist_node *n)
{
        if (!hlist_unhashed(n)) {
                __hlist_del(n);
                INIT_HLIST_NODE(n);
        }
}

/**
 * hlist_add_head - add a new entry at the beginning of the hlist
 * @param n new entry to be added
 * @param h hlist head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
{
        struct hlist_node *first = h->first;
        n->next = first;
        if (first)
                first->pprev = &n->next;
        h->first = n;
        n->pprev = &h->first;
}

/**
 * hlist_add_before - add a new entry before the one specified
 * @param n    new entry to be added
 * @param next hlist node to add it before, which must be non-NULL
 */
static inline void hlist_add_before(struct hlist_node *n,
                                    struct hlist_node *next)
{
        n->pprev = next->pprev;
        n->next = next;
        next->pprev = &n->next;
        *(n->pprev) = n;
}

/**
 * hlist_add_behind - add a new entry after the one specified
 * @param n    new entry to be added
 * @param prev hlist node to add it after, which must be non-NULL
 */
static inline void hlist_add_behind(struct hlist_node *n,
                                    struct hlist_node *prev)
{
        n->next = prev->next;
        prev->next = n;
        n->pprev = &prev->next;

        if (n->next)
                n->next->pprev = &n->next;
}

/**
 * hlist_add_fake - create a fake hlist consisting of a single headless node
 * @param n Node to make a fake list out of
 *
 * This makes @a n appear to be its own predecessor on a headless hlist.
 * The point of this is to allow things like hlist_del() to work correctly
 * in cases where there is no list.
 */
static inline void hlist_add_fake(struct hlist_node *n)
{
        n->pprev = &n->next;
}

/**
 * hlist_fake: Is this node a fake hlist?
 * @param h Node to check for being a self-referential fake hlist.
 */
static inline bool hlist_fake(struct hlist_node *h)
{
        return h->pprev == &h->next;
}

/**
 * hlist_is_singular_node - is node the only element of the specified hlist?
 * @param n Node to check for singularity.
 * @param h Header for potentially singular list.
 *
 * Check whether the node is the only node of the head without
 * accessing head, thus avoiding unnecessary cache misses.
 */
static inline bool
hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
{
        return !n->next && n->pprev == &h->first;
}

/**
 * hlist_move_list - Move an hlist
 * @param old hlist_head for old list.
 * @param new hlist_head for new list.
 *
 * Move a list from one list head to another. Fixup the pprev
 * reference of the first entry if it exists.
 */
static inline void hlist_move_list(struct hlist_head *old,
                                   struct hlist_head *new)
{
        new->first = old->first;
        if (new->first)
                new->first->pprev = &new->first;
        old->first = NULL;
}

#define hlist_entry(ptr, type, member) container_of(ptr, type, member)

#define hlist_for_each(pos, head) \
        for (pos = (head)->first; pos ; pos = pos->next)

#define hlist_for_each_safe(pos, n, head) \
        for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
             pos = n)

#define hlist_entry_safe(ptr, type, member) \
        ({ typeof(ptr) ____ptr = (ptr); \
           ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
        })

/**
 * hlist_for_each_entry - iterate over list of given type
 * @param pos    the type * to use as a loop cursor.
 * @param head   the head for your list.
 * @param member the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry(pos, head, member)                         \
        for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
             pos;                                                       \
             pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
 * @param pos    the type * to use as a loop cursor.
 * @param member the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_continue(pos, member)                      \
        for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
             pos;                                                       \
             pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
 * @param pos    the type * to use as a loop cursor.
 * @param member the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_from(pos, member)                          \
        for (; pos;                                                     \
             pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))

/**
 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @param pos    the type * to use as a loop cursor.
 * @param n      a &struct hlist_node to use as temporary storage
 * @param head   the head for your list.
 * @param member the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_safe(pos, n, head, member)         \
        for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
             pos && ({ n = pos->member.next; 1; });                     \
             pos = hlist_entry_safe(n, typeof(*pos), member))

#endif /* OPENOCD_HELPER_LIST_H */