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1 /*
2 * Copyright (c) 2012, 2013 Nicira, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #ifndef HEAP_H
18 #define HEAP_H 1
19
20 #include <stdbool.h>
21 #include <stddef.h>
22 #include <stdint.h>
23
24 /* A heap node, to be embedded inside the data structure in the heap. */
25 struct heap_node {
26 size_t idx;
27 uint64_t priority;
28 };
29
30 /* A max-heap. */
31 struct heap {
32 struct heap_node **array; /* Data in elements 1...n, element 0 unused. */
33 size_t n; /* Number of nodes currently in the heap. */
34 size_t allocated; /* Max 'n' before 'array' must be enlarged. */
35 };
36
37 /* Initialization. */
38 void heap_init(struct heap *);
39 void heap_destroy(struct heap *);
40 void heap_clear(struct heap *);
41 void heap_swap(struct heap *a, struct heap *b);
42 static inline size_t heap_count(const struct heap *);
43 static inline bool heap_is_empty(const struct heap *);
44
45 /* Insertion and deletion. */
46 void heap_insert(struct heap *, struct heap_node *, uint64_t priority);
47 void heap_change(struct heap *, struct heap_node *, uint64_t priority);
48 void heap_remove(struct heap *, struct heap_node *);
49 static inline struct heap_node *heap_pop(struct heap *);
50
51 /* Maximum. */
52 static inline struct heap_node *heap_max(const struct heap *);
53
54 /* The "raw" functions below do not preserve the heap invariants. After you
55 * call them, heap_max() will not necessarily return the right value until you
56 * subsequently call heap_rebuild(). */
57 void heap_raw_insert(struct heap *, struct heap_node *, uint64_t priority);
58 static inline void heap_raw_change(struct heap_node *, uint64_t priority);
59 void heap_raw_remove(struct heap *, struct heap_node *);
60 void heap_rebuild(struct heap *);
61
62 /* Iterates through each NODE in HEAP, where NODE->MEMBER must be a "struct
63 * heap_node". Iterates in heap level order, which in particular means that
64 * the first node visited is the maximum value in the heap.
65 *
66 * If a heap_raw_*() function has been called without a later call to
67 * heap_rebuild(), then the first node visited may not be the maximum
68 * element. */
69 #define HEAP_FOR_EACH(NODE, MEMBER, HEAP) \
70 for (((HEAP)->n > 0 \
71 ? INIT_CONTAINER(NODE, (HEAP)->array[1], MEMBER) \
72 : ((NODE) = NULL, (void) 0)); \
73 (NODE) != NULL; \
74 ((NODE)->MEMBER.idx < (HEAP)->n \
75 ? ASSIGN_CONTAINER(NODE, \
76 (HEAP)->array[(NODE)->MEMBER.idx + 1], \
77 MEMBER) \
78 : ((NODE) = NULL, (void) 0)))
79 \f
80 /* Returns the index of the node that is the parent of the node with the given
81 * 'idx' within a heap. */
82 static inline size_t
83 heap_parent__(size_t idx)
84 {
85 return idx / 2;
86 }
87
88 /* Returns the index of the node that is the left child of the node with the
89 * given 'idx' within a heap. */
90 static inline size_t
91 heap_left__(size_t idx)
92 {
93 return idx * 2;
94 }
95
96 /* Returns the index of the node that is the right child of the node with the
97 * given 'idx' within a heap. */
98 static inline size_t
99 heap_right__(size_t idx)
100 {
101 return idx * 2 + 1;
102 }
103
104 /* Returns true if 'idx' is the index of a leaf node in 'heap', false
105 * otherwise. */
106 static inline bool
107 heap_is_leaf__(const struct heap *heap, size_t idx)
108 {
109 return heap_left__(idx) > heap->n;
110 }
111
112 /* Returns the number of elements in 'heap'. */
113 static inline size_t
114 heap_count(const struct heap *heap)
115 {
116 return heap->n;
117 }
118
119 /* Returns true if 'heap' is empty, false if it contains at least one
120 * element. */
121 static inline bool
122 heap_is_empty(const struct heap *heap)
123 {
124 return heap->n == 0;
125 }
126
127 /* Returns the largest element in 'heap'.
128 *
129 * The caller must ensure that 'heap' contains at least one element.
130 *
131 * The return value may be wrong (i.e. not the maximum element but some other
132 * element) if a heap_raw_*() function has been called without a later call to
133 * heap_rebuild(). */
134 static inline struct heap_node *
135 heap_max(const struct heap *heap)
136 {
137 return heap->array[1];
138 }
139
140 /* Removes an arbitrary node from 'heap', in O(1), maintaining the heap
141 * invariant. Returns the node removed.
142 *
143 * The caller must ensure that 'heap' contains at least one element. */
144 static inline struct heap_node *
145 heap_pop(struct heap *heap)
146 {
147 return heap->array[heap->n--];
148 }
149
150 /* Changes the priority of 'node' (which must be in 'heap') to 'priority'.
151 *
152 * After this call, heap_max() will no longer necessarily return the maximum
153 * value in the heap, and HEAP_FOR_EACH will no longer necessarily iterate in
154 * heap level order, until the next call to heap_rebuild(heap).
155 *
156 * This takes time O(1). */
157 static inline void
158 heap_raw_change(struct heap_node *node, uint64_t priority)
159 {
160 node->priority = priority;
161 }
162
163 #endif /* heap.h */