1 | /* vi: set sw=4 ts=4: */
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2 |
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3 | #include "list.h"
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4 |
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5 | /*
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6 | * Insert a new entry between two known consecutive entries.
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7 | *
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8 | * This is only for internal list manipulation where we know
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9 | * the prev/next entries already!
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10 | */
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11 | void __list_add(struct list_head * add,
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12 | struct list_head * prev,
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13 | struct list_head * next)
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14 | {
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15 | next->prev = add;
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16 | add->next = next;
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17 | add->prev = prev;
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18 | prev->next = add;
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19 | }
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20 |
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21 | /*
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22 | * list_add - add a new entry
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23 | * @add: new entry to be added
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24 | * @head: list head to add it after
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25 | *
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26 | * Insert a new entry after the specified head.
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27 | * This is good for implementing stacks.
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28 | */
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29 | void list_add(struct list_head *add, struct list_head *head)
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30 | {
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31 | __list_add(add, head, head->next);
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32 | }
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33 |
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34 | /*
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35 | * list_add_tail - add a new entry
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36 | * @add: new entry to be added
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37 | * @head: list head to add it before
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38 | *
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39 | * Insert a new entry before the specified head.
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40 | * This is useful for implementing queues.
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41 | */
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42 | void list_add_tail(struct list_head *add, struct list_head *head)
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43 | {
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44 | __list_add(add, head->prev, head);
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45 | }
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46 |
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47 | /*
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48 | * Delete a list entry by making the prev/next entries
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49 | * point to each other.
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50 | *
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51 | * This is only for internal list manipulation where we know
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52 | * the prev/next entries already!
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53 | */
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54 | void __list_del(struct list_head * prev, struct list_head * next)
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55 | {
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56 | next->prev = prev;
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57 | prev->next = next;
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58 | }
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59 |
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60 | /*
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61 | * list_del - deletes entry from list.
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62 | * @entry: the element to delete from the list.
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63 | *
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64 | * list_empty() on @entry does not return true after this, @entry is
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65 | * in an undefined state.
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66 | */
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67 | void list_del(struct list_head *entry)
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68 | {
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69 | __list_del(entry->prev, entry->next);
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70 | }
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71 |
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72 | /*
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73 | * list_del_init - deletes entry from list and reinitialize it.
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74 | * @entry: the element to delete from the list.
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75 | */
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76 | void list_del_init(struct list_head *entry)
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77 | {
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78 | __list_del(entry->prev, entry->next);
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79 | INIT_LIST_HEAD(entry);
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80 | }
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81 |
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82 | /*
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83 | * list_empty - tests whether a list is empty
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84 | * @head: the list to test.
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85 | */
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86 | int list_empty(struct list_head *head)
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87 | {
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88 | return head->next == head;
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89 | }
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90 |
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91 | /*
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92 | * list_splice - join two lists
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93 | * @list: the new list to add.
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94 | * @head: the place to add it in the first list.
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95 | */
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96 | void list_splice(struct list_head *list, struct list_head *head)
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97 | {
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98 | struct list_head *first = list->next;
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99 |
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100 | if (first != list) {
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101 | struct list_head *last = list->prev;
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102 | struct list_head *at = head->next;
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103 |
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104 | first->prev = head;
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105 | head->next = first;
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106 |
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107 | last->next = at;
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108 | at->prev = last;
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109 | }
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110 | }
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