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1 | #ifndef _LTTNG_PRIO_HEAP_H |
2 | #define _LTTNG_PRIO_HEAP_H | |
f3bc08c5 MD |
3 | |
4 | /* | |
162769ef MD |
5 | * prio_heap.h |
6 | * | |
7 | * Static-sized priority heap containing pointers. Based on CLRS, | |
8 | * chapter 6. | |
9 | * | |
10 | * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
11 | * | |
12 | * Permission is hereby granted, free of charge, to any person obtaining a copy | |
13 | * of this software and associated documentation files (the "Software"), to deal | |
14 | * in the Software without restriction, including without limitation the rights | |
15 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
16 | * copies of the Software, and to permit persons to whom the Software is | |
17 | * furnished to do so, subject to the following conditions: | |
18 | * | |
19 | * The above copyright notice and this permission notice shall be included in | |
20 | * all copies or substantial portions of the Software. | |
f3bc08c5 MD |
21 | */ |
22 | ||
c9891db2 MD |
23 | #include <linux/gfp.h> |
24 | ||
25 | struct ptr_heap { | |
26 | size_t size, max; | |
27 | void **ptrs; | |
28 | int (*gt)(void *a, void *b); | |
29 | }; | |
f3bc08c5 MD |
30 | |
31 | /** | |
32 | * heap_maximum - return the largest element in the heap | |
33 | * @heap: the heap to be operated on | |
34 | * | |
35 | * Returns the largest element in the heap, without performing any modification | |
36 | * to the heap structure. Returns NULL if the heap is empty. | |
37 | */ | |
38 | static inline void *heap_maximum(const struct ptr_heap *heap) | |
39 | { | |
40 | return heap->size ? heap->ptrs[0] : NULL; | |
41 | } | |
42 | ||
c9891db2 MD |
43 | /** |
44 | * heap_init - initialize the heap | |
45 | * @heap: the heap to initialize | |
46 | * @size: maximum number of elements | |
47 | * @gfp: allocation flags | |
48 | * @gt: function to compare the elements | |
49 | * | |
50 | * Returns -ENOMEM if out of memory. | |
51 | */ | |
52 | extern int heap_init(struct ptr_heap *heap, size_t size, | |
53 | gfp_t gfpmask, int gt(void *a, void *b)); | |
54 | ||
55 | /** | |
56 | * heap_free - free the heap | |
57 | * @heap: the heap to free | |
58 | */ | |
59 | extern void heap_free(struct ptr_heap *heap); | |
60 | ||
61 | /** | |
62 | * heap_insert - insert an element into the heap | |
63 | * @heap: the heap to be operated on | |
64 | * | |
65 | * Insert an element into the heap. If the heap is full, return the | |
66 | * largest element between those previously present in the heap and the | |
67 | * element being added, else return NULL. | |
68 | */ | |
69 | extern void *heap_insert(struct ptr_heap *heap, void *p); | |
f3bc08c5 MD |
70 | |
71 | /** | |
72 | * heap_remove - remove the largest element from the heap | |
73 | * @heap: the heap to be operated on | |
74 | * | |
75 | * Returns the largest element in the heap. It removes this element from the | |
76 | * heap. Returns NULL if the heap is empty. | |
77 | */ | |
78 | extern void *heap_remove(struct ptr_heap *heap); | |
79 | ||
80 | /** | |
81 | * heap_cherrypick - remove a given element from the heap | |
82 | * @heap: the heap to be operated on | |
83 | * @p: the element | |
84 | * | |
85 | * Remove the given element from the heap. Return the element if present, else | |
86 | * return NULL. This algorithm has a complexity of O(n), which is higher than | |
87 | * O(log(n)) provided by the rest of this API. | |
88 | */ | |
89 | extern void *heap_cherrypick(struct ptr_heap *heap, void *p); | |
90 | ||
91 | /** | |
92 | * heap_replace_max - replace the the largest element from the heap | |
93 | * @heap: the heap to be operated on | |
94 | * @p: the pointer to be inserted as topmost element replacement | |
95 | * | |
96 | * Returns the largest element in the heap. It removes this element from the | |
97 | * heap. The heap is rebalanced only once after the insertion. Returns NULL if | |
98 | * the heap is empty. | |
99 | * | |
100 | * This is the equivalent of calling heap_remove() and then heap_insert(), but | |
101 | * it only rebalances the heap once. | |
102 | */ | |
103 | extern void *heap_replace_max(struct ptr_heap *heap, void *p); | |
104 | ||
162769ef | 105 | #endif /* _LTTNG_PRIO_HEAP_H */ |