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1eb0c69c MD |
1 | /* |
2 | * prio_heap.c | |
3 | * | |
4 | * Static-sized priority heap containing pointers. Based on CLRS, | |
5 | * chapter 6. | |
6 | * | |
7 | * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
8 | * | |
9 | * Permission is hereby granted, free of charge, to any person obtaining a copy | |
10 | * of this software and associated documentation files (the "Software"), to deal | |
11 | * in the Software without restriction, including without limitation the rights | |
12 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
13 | * copies of the Software, and to permit persons to whom the Software is | |
14 | * furnished to do so, subject to the following conditions: | |
15 | * | |
16 | * The above copyright notice and this permission notice shall be included in | |
17 | * all copies or substantial portions of the Software. | |
18 | */ | |
19 | ||
20 | #include <babeltrace/prio_heap.h> | |
21 | #include <errno.h> | |
22 | #include <stdlib.h> | |
23 | #include <string.h> | |
24 | ||
25 | #ifndef max_t | |
26 | #define max_t(type, a, b) \ | |
27 | ((type) (a) > (type) (b) ? (type) (a) : (type) (b)) | |
28 | #endif | |
29 | ||
30 | static __attribute__((unused)) | |
31 | size_t parent(size_t i) | |
32 | { | |
33 | return i >> 1; | |
34 | } | |
35 | ||
36 | static | |
37 | size_t left(size_t i) | |
38 | { | |
39 | return i << 1; | |
40 | } | |
41 | ||
42 | static | |
43 | size_t right(size_t i) | |
44 | { | |
45 | return (i << 1) + 1; | |
46 | } | |
47 | ||
48 | static | |
49 | int heap_grow(struct ptr_heap *heap, size_t new_len) | |
50 | { | |
51 | void **new_ptrs; | |
52 | ||
53 | if (heap->alloc_len >= new_len) | |
54 | return 0; | |
55 | ||
56 | heap->alloc_len = max_t(size_t, new_len, heap->alloc_len << 1); | |
57 | new_ptrs = calloc(heap->alloc_len, sizeof(void *)); | |
58 | if (!new_ptrs) | |
59 | return -ENOMEM; | |
60 | if (heap->ptrs) | |
61 | memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *)); | |
62 | free(heap->ptrs); | |
63 | heap->ptrs = new_ptrs; | |
64 | return 0; | |
65 | } | |
66 | ||
67 | static | |
68 | int heap_set_len(struct ptr_heap *heap, size_t new_len) | |
69 | { | |
70 | int ret; | |
71 | ||
72 | ret = heap_grow(heap, new_len); | |
73 | if (ret) | |
74 | return ret; | |
75 | heap->len = new_len; | |
76 | return 0; | |
77 | } | |
78 | ||
79 | int heap_init(struct ptr_heap *heap, size_t alloc_len, | |
80 | int gt(void *a, void *b)) | |
81 | { | |
82 | heap->ptrs = NULL; | |
83 | heap->len = 0; | |
84 | heap->alloc_len = 0; | |
85 | heap->gt = gt; | |
86 | /* | |
87 | * Minimum size allocated is 1 entry to ensure memory allocation | |
88 | * never fails within heap_replace_max. | |
89 | */ | |
90 | return heap_grow(heap, max_t(size_t, 1, alloc_len)); | |
91 | } | |
92 | ||
93 | void heap_free(struct ptr_heap *heap) | |
94 | { | |
95 | free(heap->ptrs); | |
96 | } | |
97 | ||
98 | static void heapify(struct ptr_heap *heap, size_t i) | |
99 | { | |
100 | void **ptrs = heap->ptrs; | |
101 | size_t l, r, largest; | |
102 | ||
103 | for (;;) { | |
104 | l = left(i); | |
105 | r = right(i); | |
106 | if (l <= heap->len && ptrs[l] > ptrs[i]) | |
107 | largest = l; | |
108 | else | |
109 | largest = i; | |
110 | if (r <= heap->len && ptrs[r] > ptrs[largest]) | |
111 | largest = r; | |
112 | if (largest != i) { | |
113 | void *tmp; | |
114 | ||
115 | tmp = ptrs[i]; | |
116 | ptrs[i] = ptrs[largest]; | |
117 | ptrs[largest] = tmp; | |
118 | i = largest; | |
119 | continue; | |
120 | } else { | |
121 | break; | |
122 | } | |
123 | } | |
124 | } | |
125 | ||
126 | void *heap_replace_max(struct ptr_heap *heap, void *p) | |
127 | { | |
128 | void *res; | |
129 | void **ptrs = heap->ptrs; | |
130 | ||
131 | if (!heap->len) { | |
132 | (void) heap_set_len(heap, 1); | |
133 | ptrs[0] = p; | |
134 | return NULL; | |
135 | } | |
136 | ||
137 | /* Replace the current max and heapify */ | |
138 | res = ptrs[0]; | |
139 | ptrs[0] = p; | |
140 | heapify(heap, 0); | |
141 | return res; | |
142 | } | |
143 | ||
144 | int heap_insert(struct ptr_heap *heap, void *p) | |
145 | { | |
146 | void **ptrs = heap->ptrs; | |
147 | int ret; | |
148 | ||
149 | ret = heap_set_len(heap, heap->len + 1); | |
150 | if (ret) | |
151 | return ret; | |
152 | /* Add the element to the end */ | |
153 | ptrs[heap->len - 1] = p; | |
154 | /* rebalance */ | |
155 | heapify(heap, 0); | |
156 | return 0; | |
157 | } | |
158 | ||
159 | void *heap_remove(struct ptr_heap *heap) | |
160 | { | |
161 | void **ptrs = heap->ptrs; | |
162 | ||
163 | switch (heap->len) { | |
164 | case 0: | |
165 | return NULL; | |
166 | case 1: | |
167 | (void) heap_set_len(heap, 0); | |
168 | return ptrs[0]; | |
169 | } | |
170 | /* Shrink, replace the current max by previous last entry and heapify */ | |
171 | heap_set_len(heap, heap->len - 1); | |
172 | return heap_replace_max(heap, ptrs[heap->len - 1]); | |
173 | } | |
174 | ||
175 | void *heap_cherrypick(struct ptr_heap *heap, void *p) | |
176 | { | |
177 | void **ptrs = heap->ptrs; | |
178 | size_t pos, len = heap->len; | |
179 | ||
180 | for (pos = 0; pos < len; pos++) | |
181 | if (ptrs[pos] == p) | |
182 | goto found; | |
183 | return NULL; | |
184 | found: | |
185 | if (heap->len == 1) { | |
186 | (void) heap_set_len(heap, 0); | |
187 | return ptrs[0]; | |
188 | } | |
189 | /* Replace p with previous last entry and heapify. */ | |
190 | heap_set_len(heap, heap->len - 1); | |
191 | ptrs[pos] = ptrs[heap->len - 1]; | |
192 | heapify(heap, pos); | |
193 | return p; | |
194 | } |