Commit | Line | Data |
---|---|---|
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 | ||
557255e5 | 30 | static |
1eb0c69c MD |
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 | ||
557255e5 MD |
48 | /* |
49 | * Copy of heap->ptrs pointer is invalid after heap_grow. | |
50 | */ | |
1eb0c69c MD |
51 | static |
52 | int heap_grow(struct ptr_heap *heap, size_t new_len) | |
53 | { | |
54 | void **new_ptrs; | |
55 | ||
56 | if (heap->alloc_len >= new_len) | |
57 | return 0; | |
58 | ||
59 | heap->alloc_len = max_t(size_t, new_len, heap->alloc_len << 1); | |
60 | new_ptrs = calloc(heap->alloc_len, sizeof(void *)); | |
61 | if (!new_ptrs) | |
62 | return -ENOMEM; | |
63 | if (heap->ptrs) | |
64 | memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *)); | |
65 | free(heap->ptrs); | |
66 | heap->ptrs = new_ptrs; | |
67 | return 0; | |
68 | } | |
69 | ||
70 | static | |
71 | int heap_set_len(struct ptr_heap *heap, size_t new_len) | |
72 | { | |
73 | int ret; | |
74 | ||
75 | ret = heap_grow(heap, new_len); | |
76 | if (ret) | |
77 | return ret; | |
78 | heap->len = new_len; | |
79 | return 0; | |
80 | } | |
81 | ||
82 | int heap_init(struct ptr_heap *heap, size_t alloc_len, | |
83 | int gt(void *a, void *b)) | |
84 | { | |
85 | heap->ptrs = NULL; | |
86 | heap->len = 0; | |
87 | heap->alloc_len = 0; | |
88 | heap->gt = gt; | |
89 | /* | |
90 | * Minimum size allocated is 1 entry to ensure memory allocation | |
91 | * never fails within heap_replace_max. | |
92 | */ | |
93 | return heap_grow(heap, max_t(size_t, 1, alloc_len)); | |
94 | } | |
95 | ||
96 | void heap_free(struct ptr_heap *heap) | |
97 | { | |
98 | free(heap->ptrs); | |
99 | } | |
100 | ||
101 | static void heapify(struct ptr_heap *heap, size_t i) | |
102 | { | |
103 | void **ptrs = heap->ptrs; | |
104 | size_t l, r, largest; | |
105 | ||
106 | for (;;) { | |
107 | l = left(i); | |
108 | r = right(i); | |
109 | if (l <= heap->len && ptrs[l] > ptrs[i]) | |
110 | largest = l; | |
111 | else | |
112 | largest = i; | |
113 | if (r <= heap->len && ptrs[r] > ptrs[largest]) | |
114 | largest = r; | |
115 | if (largest != i) { | |
116 | void *tmp; | |
117 | ||
118 | tmp = ptrs[i]; | |
119 | ptrs[i] = ptrs[largest]; | |
120 | ptrs[largest] = tmp; | |
121 | i = largest; | |
122 | continue; | |
123 | } else { | |
124 | break; | |
125 | } | |
126 | } | |
127 | } | |
128 | ||
129 | void *heap_replace_max(struct ptr_heap *heap, void *p) | |
130 | { | |
131 | void *res; | |
1eb0c69c MD |
132 | |
133 | if (!heap->len) { | |
134 | (void) heap_set_len(heap, 1); | |
557255e5 | 135 | heap->ptrs[0] = p; |
1eb0c69c MD |
136 | return NULL; |
137 | } | |
138 | ||
139 | /* Replace the current max and heapify */ | |
557255e5 MD |
140 | res = heap->ptrs[0]; |
141 | heap->ptrs[0] = p; | |
1eb0c69c MD |
142 | heapify(heap, 0); |
143 | return res; | |
144 | } | |
145 | ||
146 | int heap_insert(struct ptr_heap *heap, void *p) | |
147 | { | |
557255e5 MD |
148 | void **ptrs; |
149 | size_t pos; | |
1eb0c69c MD |
150 | int ret; |
151 | ||
152 | ret = heap_set_len(heap, heap->len + 1); | |
153 | if (ret) | |
154 | return ret; | |
557255e5 | 155 | ptrs = heap->ptrs; |
1eb0c69c MD |
156 | /* Add the element to the end */ |
157 | ptrs[heap->len - 1] = p; | |
557255e5 MD |
158 | pos = heap->len - 1; |
159 | /* Bubble it up to the appropriate position. */ | |
160 | for (;;) { | |
161 | if (pos > 0 && heap->gt(ptrs[pos], ptrs[parent(pos)])) { | |
162 | void *tmp; | |
163 | ||
164 | /* Need to exchange */ | |
165 | tmp = ptrs[pos]; | |
166 | ptrs[pos] = ptrs[parent(pos)]; | |
167 | ptrs[parent(pos)] = tmp; | |
168 | pos = parent(pos); | |
169 | /* | |
170 | * No need to rebalance: if we are larger than | |
171 | * our parent, we are necessarily larger than | |
172 | * its other child. | |
173 | */ | |
174 | } else { | |
175 | break; | |
176 | } | |
177 | } | |
1eb0c69c MD |
178 | return 0; |
179 | } | |
180 | ||
181 | void *heap_remove(struct ptr_heap *heap) | |
182 | { | |
1eb0c69c MD |
183 | switch (heap->len) { |
184 | case 0: | |
185 | return NULL; | |
186 | case 1: | |
187 | (void) heap_set_len(heap, 0); | |
557255e5 | 188 | return heap->ptrs[0]; |
1eb0c69c MD |
189 | } |
190 | /* Shrink, replace the current max by previous last entry and heapify */ | |
191 | heap_set_len(heap, heap->len - 1); | |
557255e5 | 192 | return heap_replace_max(heap, heap->ptrs[heap->len - 1]); |
1eb0c69c MD |
193 | } |
194 | ||
195 | void *heap_cherrypick(struct ptr_heap *heap, void *p) | |
196 | { | |
1eb0c69c MD |
197 | size_t pos, len = heap->len; |
198 | ||
199 | for (pos = 0; pos < len; pos++) | |
557255e5 | 200 | if (heap->ptrs[pos] == p) |
1eb0c69c MD |
201 | goto found; |
202 | return NULL; | |
203 | found: | |
204 | if (heap->len == 1) { | |
205 | (void) heap_set_len(heap, 0); | |
557255e5 | 206 | return heap->ptrs[0]; |
1eb0c69c MD |
207 | } |
208 | /* Replace p with previous last entry and heapify. */ | |
209 | heap_set_len(heap, heap->len - 1); | |
557255e5 | 210 | heap->ptrs[pos] = heap->ptrs[heap->len - 1]; |
1eb0c69c MD |
211 | heapify(heap, pos); |
212 | return p; | |
213 | } |