Annotate prio heap likely branch
[babeltrace.git] / include / babeltrace / prio_heap.h
1 #ifndef _BABELTRACE_PRIO_HEAP_H
2 #define _BABELTRACE_PRIO_HEAP_H
3
4 /*
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.
21 */
22
23 #include <unistd.h>
24 #include <babeltrace/babeltrace-internal.h>
25
26 struct ptr_heap {
27 size_t len, alloc_len;
28 void **ptrs;
29 int (*gt)(void *a, void *b);
30 };
31
32 #ifdef DEBUG_HEAP
33 void check_heap(const struct ptr_heap *heap);
34 #else
35 static inline
36 void check_heap(const struct ptr_heap *heap)
37 {
38 }
39 #endif
40
41 /**
42 * heap_maximum - return the largest element in the heap
43 * @heap: the heap to be operated on
44 *
45 * Returns the largest element in the heap, without performing any modification
46 * to the heap structure. Returns NULL if the heap is empty.
47 */
48 static inline void *heap_maximum(const struct ptr_heap *heap)
49 {
50 check_heap(heap);
51 return likely(heap->len) ? heap->ptrs[0] : NULL;
52 }
53
54 /**
55 * heap_init - initialize the heap
56 * @heap: the heap to initialize
57 * @alloc_len: number of elements initially allocated
58 * @gt: function to compare the elements
59 *
60 * Returns -ENOMEM if out of memory.
61 */
62 extern int heap_init(struct ptr_heap *heap,
63 size_t alloc_len,
64 int gt(void *a, void *b));
65
66 /**
67 * heap_free - free the heap
68 * @heap: the heap to free
69 */
70 extern void heap_free(struct ptr_heap *heap);
71
72 /**
73 * heap_insert - insert an element into the heap
74 * @heap: the heap to be operated on
75 * @p: the element to add
76 *
77 * Insert an element into the heap.
78 *
79 * Returns -ENOMEM if out of memory.
80 */
81 extern int heap_insert(struct ptr_heap *heap, void *p);
82
83 /**
84 * heap_remove - remove the largest element from the heap
85 * @heap: the heap to be operated on
86 *
87 * Returns the largest element in the heap. It removes this element from the
88 * heap. Returns NULL if the heap is empty.
89 */
90 extern void *heap_remove(struct ptr_heap *heap);
91
92 /**
93 * heap_cherrypick - remove a given element from the heap
94 * @heap: the heap to be operated on
95 * @p: the element
96 *
97 * Remove the given element from the heap. Return the element if present, else
98 * return NULL. This algorithm has a complexity of O(n), which is higher than
99 * O(log(n)) provided by the rest of this API.
100 */
101 extern void *heap_cherrypick(struct ptr_heap *heap, void *p);
102
103 /**
104 * heap_replace_max - replace the the largest element from the heap
105 * @heap: the heap to be operated on
106 * @p: the pointer to be inserted as topmost element replacement
107 *
108 * Returns the largest element in the heap. It removes this element from the
109 * heap. The heap is rebalanced only once after the insertion. Returns NULL if
110 * the heap is empty.
111 *
112 * This is the equivalent of calling heap_remove() and then heap_insert(), but
113 * it only rebalances the heap once. It never allocates memory.
114 */
115 extern void *heap_replace_max(struct ptr_heap *heap, void *p);
116
117 #endif /* _BABELTRACE_PRIO_HEAP_H */
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