362 lines
8.8 KiB
C
362 lines
8.8 KiB
C
/*
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* Copyright (C) 2008 Karel Zak <kzak@redhat.com>
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* Copyright (C) 1999-2008 by Theodore Ts'o
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*
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* This file may be redistributed under the terms of the
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* GNU Lesser General Public License.
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*
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* (based on list.h from e2fsprogs)
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* Merge sort based on kernel's implementation.
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*/
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#ifndef UTIL_LINUX_LIST_H
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#define UTIL_LINUX_LIST_H
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#include "c.h"
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/* TODO: use AC_C_INLINE */
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#ifdef __GNUC__
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#define _INLINE_ static __inline__
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#else /* For Watcom C */
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#define _INLINE_ static inline
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#endif
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/*
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* Simple doubly linked list implementation.
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*
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* Some of the internal functions ("__xxx") are useful when
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* manipulating whole lists rather than single entries, as
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* sometimes we already know the next/prev entries and we can
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* generate better code by using them directly rather than
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* using the generic single-entry routines.
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*/
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struct list_head {
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struct list_head *next, *prev;
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};
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#define INIT_LIST_HEAD(ptr) do { \
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(ptr)->next = (ptr); (ptr)->prev = (ptr); \
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} while (0)
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/*
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* Insert a new entry between two known consecutive entries.
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*
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* This is only for internal list manipulation where we know
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* the prev/next entries already!
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*/
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_INLINE_ void __list_add(struct list_head * add,
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struct list_head * prev,
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struct list_head * next)
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{
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next->prev = add;
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add->next = next;
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add->prev = prev;
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prev->next = add;
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}
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/**
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* list_add - add a new entry
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* @add: new entry to be added
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* @head: list head to add it after
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*
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* Insert a new entry after the specified head.
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* This is good for implementing stacks.
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*/
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_INLINE_ void list_add(struct list_head *add, struct list_head *head)
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{
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__list_add(add, head, head->next);
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}
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/**
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* list_add_tail - add a new entry
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* @add: new entry to be added
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* @head: list head to add it before
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*
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* Insert a new entry before the specified head.
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* This is useful for implementing queues.
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*/
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_INLINE_ void list_add_tail(struct list_head *add, struct list_head *head)
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{
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__list_add(add, head->prev, head);
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}
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/*
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* Delete a list entry by making the prev/next entries
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* point to each other.
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*
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* This is only for internal list manipulation where we know
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* the prev/next entries already!
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*/
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_INLINE_ void __list_del(struct list_head * prev,
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struct list_head * next)
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{
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next->prev = prev;
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prev->next = next;
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}
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/**
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* list_del - deletes entry from list.
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* @entry: the element to delete from the list.
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*
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* list_empty() on @entry does not return true after this, @entry is
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* in an undefined state.
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*/
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_INLINE_ void list_del(struct list_head *entry)
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{
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__list_del(entry->prev, entry->next);
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}
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/**
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* list_del_init - deletes entry from list and reinitialize it.
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* @entry: the element to delete from the list.
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*/
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_INLINE_ void list_del_init(struct list_head *entry)
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{
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__list_del(entry->prev, entry->next);
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INIT_LIST_HEAD(entry);
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}
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/**
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* list_empty - tests whether a list is empty
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* @head: the list to test.
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*/
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_INLINE_ int list_empty(struct list_head *head)
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{
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return head->next == head;
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}
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/**
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* list_entry_is_last - tests whether is entry last in the list
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* @entry: the entry to test.
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* @head: the list to test.
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*/
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_INLINE_ int list_entry_is_last(struct list_head *entry, struct list_head *head)
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{
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return head->prev == entry;
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}
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/**
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* list_entry_is_first - tests whether is entry first in the list
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* @entry: the entry to test.
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* @head: the list to test.
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*/
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_INLINE_ int list_entry_is_first(struct list_head *entry, struct list_head *head)
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{
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return head->next == entry;
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}
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/**
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* list_splice - join two lists
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* @list: the new list to add.
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* @head: the place to add it in the first list.
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*/
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_INLINE_ void list_splice(struct list_head *list, struct list_head *head)
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{
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struct list_head *first = list->next;
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if (first != list) {
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struct list_head *last = list->prev;
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struct list_head *at = head->next;
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first->prev = head;
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head->next = first;
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last->next = at;
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at->prev = last;
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}
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}
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/**
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* list_entry - get the struct for this entry
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* @ptr: the &struct list_head pointer.
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* @type: the type of the struct this is embedded in.
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* @member: the name of the list_struct within the struct.
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*/
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#define list_entry(ptr, type, member) container_of(ptr, type, member)
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#define list_first_entry(head, type, member) \
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((head) && (head)->next != (head) ? list_entry((head)->next, type, member) : NULL)
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#define list_last_entry(head, type, member) \
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((head) && (head)->prev != (head) ? list_entry((head)->prev, type, member) : NULL)
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/**
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* list_for_each - iterate over elements in a list
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* @pos: the &struct list_head to use as a loop counter.
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* @head: the head for your list.
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*/
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#define list_for_each(pos, head) \
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for (pos = (head)->next; pos != (head); pos = pos->next)
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/**
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* list_for_each_backwardly - iterate over elements in a list in reverse
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* @pos: the &struct list_head to use as a loop counter.
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* @head: the head for your list.
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*/
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#define list_for_each_backwardly(pos, head) \
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for (pos = (head)->prev; pos != (head); pos = pos->prev)
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/**
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* list_for_each_safe - iterate over elements in a list, but don't dereference
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* pos after the body is done (in case it is freed)
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* @pos: the &struct list_head to use as a loop counter.
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* @pnext: the &struct list_head to use as a pointer to the next item.
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* @head: the head for your list (not included in iteration).
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*/
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#define list_for_each_safe(pos, pnext, head) \
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for (pos = (head)->next, pnext = pos->next; pos != (head); \
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pos = pnext, pnext = pos->next)
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_INLINE_ size_t list_count_entries(struct list_head *head)
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{
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struct list_head *pos;
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size_t ct = 0;
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list_for_each(pos, head)
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ct++;
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return ct;
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}
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#define MAX_LIST_LENGTH_BITS 20
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/*
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* Returns a list organized in an intermediate format suited
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* to chaining of merge() calls: null-terminated, no reserved or
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* sentinel head node, "prev" links not maintained.
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*/
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_INLINE_ struct list_head *merge(int (*cmp)(struct list_head *a,
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struct list_head *b,
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void *data),
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void *data,
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struct list_head *a, struct list_head *b)
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{
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struct list_head head, *tail = &head;
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while (a && b) {
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/* if equal, take 'a' -- important for sort stability */
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if ((*cmp)(a, b, data) <= 0) {
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tail->next = a;
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a = a->next;
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} else {
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tail->next = b;
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b = b->next;
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}
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tail = tail->next;
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}
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tail->next = a ? a : b;
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return head.next;
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}
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/*
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* Combine final list merge with restoration of standard doubly-linked
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* list structure. This approach duplicates code from merge(), but
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* runs faster than the tidier alternatives of either a separate final
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* prev-link restoration pass, or maintaining the prev links
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* throughout.
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*/
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_INLINE_ void merge_and_restore_back_links(int (*cmp)(struct list_head *a,
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struct list_head *b,
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void *data),
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void *data,
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struct list_head *head,
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struct list_head *a, struct list_head *b)
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{
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struct list_head *tail = head;
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while (a && b) {
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/* if equal, take 'a' -- important for sort stability */
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if ((*cmp)(a, b, data) <= 0) {
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tail->next = a;
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a->prev = tail;
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a = a->next;
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} else {
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tail->next = b;
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b->prev = tail;
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b = b->next;
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}
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tail = tail->next;
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}
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tail->next = a ? a : b;
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do {
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/*
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* In worst cases this loop may run many iterations.
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* Continue callbacks to the client even though no
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* element comparison is needed, so the client's cmp()
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* routine can invoke cond_resched() periodically.
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*/
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(*cmp)(tail->next, tail->next, data);
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tail->next->prev = tail;
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tail = tail->next;
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} while (tail->next);
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tail->next = head;
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head->prev = tail;
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}
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/**
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* list_sort - sort a list
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* @head: the list to sort
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* @cmp: the elements comparison function
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*
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* This function implements "merge sort", which has O(nlog(n))
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* complexity.
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*
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* The comparison function @cmp must return a negative value if @a
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* should sort before @b, and a positive value if @a should sort after
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* @b. If @a and @b are equivalent, and their original relative
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* ordering is to be preserved, @cmp must return 0.
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*/
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_INLINE_ void list_sort(struct list_head *head,
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int (*cmp)(struct list_head *a,
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struct list_head *b,
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void *data),
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void *data)
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{
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struct list_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists
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-- last slot is a sentinel */
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size_t lev; /* index into part[] */
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size_t max_lev = 0;
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struct list_head *list;
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if (list_empty(head))
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return;
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memset(part, 0, sizeof(part));
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head->prev->next = NULL;
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list = head->next;
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while (list) {
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struct list_head *cur = list;
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list = list->next;
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cur->next = NULL;
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for (lev = 0; part[lev]; lev++) {
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cur = merge(cmp, data, part[lev], cur);
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part[lev] = NULL;
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}
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if (lev > max_lev) {
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/* list passed to list_sort() too long for efficiency */
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if (lev >= ARRAY_SIZE(part) - 1)
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lev--;
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max_lev = lev;
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}
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part[lev] = cur;
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}
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for (lev = 0; lev < max_lev; lev++)
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if (part[lev])
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list = merge(cmp, data, part[lev], list);
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merge_and_restore_back_links(cmp, data, head, part[max_lev], list);
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}
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#undef _INLINE_
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#endif /* UTIL_LINUX_LIST_H */
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