Commit | Line | Data |
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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> | |
eacd552c | 24 | #include <assert.h> |
1eb0c69c MD |
25 | |
26 | #ifndef max_t | |
27 | #define max_t(type, a, b) \ | |
28 | ((type) (a) > (type) (b) ? (type) (a) : (type) (b)) | |
29 | #endif | |
30 | ||
eacd552c MD |
31 | #ifdef DEBUG_HEAP |
32 | void check_heap(const struct ptr_heap *heap) | |
33 | { | |
34 | size_t i; | |
35 | ||
36 | if (!heap->len) | |
37 | return; | |
38 | ||
39 | for (i = 1; i < heap->len; i++) | |
40 | assert(!heap->gt(heap->ptrs[i], heap->ptrs[0])); | |
41 | } | |
42 | #endif | |
43 | ||
557255e5 | 44 | static |
1eb0c69c MD |
45 | size_t parent(size_t i) |
46 | { | |
eacd552c | 47 | return (i - 1) >> 1; |
1eb0c69c MD |
48 | } |
49 | ||
50 | static | |
51 | size_t left(size_t i) | |
52 | { | |
eacd552c | 53 | return (i << 1) + 1; |
1eb0c69c MD |
54 | } |
55 | ||
56 | static | |
57 | size_t right(size_t i) | |
58 | { | |
eacd552c | 59 | return (i << 1) + 2; |
1eb0c69c MD |
60 | } |
61 | ||
557255e5 MD |
62 | /* |
63 | * Copy of heap->ptrs pointer is invalid after heap_grow. | |
64 | */ | |
1eb0c69c MD |
65 | static |
66 | int heap_grow(struct ptr_heap *heap, size_t new_len) | |
67 | { | |
68 | void **new_ptrs; | |
69 | ||
70 | if (heap->alloc_len >= new_len) | |
71 | return 0; | |
72 | ||
73 | heap->alloc_len = max_t(size_t, new_len, heap->alloc_len << 1); | |
74 | new_ptrs = calloc(heap->alloc_len, sizeof(void *)); | |
75 | if (!new_ptrs) | |
76 | return -ENOMEM; | |
77 | if (heap->ptrs) | |
78 | memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *)); | |
79 | free(heap->ptrs); | |
80 | heap->ptrs = new_ptrs; | |
81 | return 0; | |
82 | } | |
83 | ||
84 | static | |
85 | int heap_set_len(struct ptr_heap *heap, size_t new_len) | |
86 | { | |
87 | int ret; | |
88 | ||
89 | ret = heap_grow(heap, new_len); | |
90 | if (ret) | |
91 | return ret; | |
92 | heap->len = new_len; | |
93 | return 0; | |
94 | } | |
95 | ||
96 | int heap_init(struct ptr_heap *heap, size_t alloc_len, | |
97 | int gt(void *a, void *b)) | |
98 | { | |
99 | heap->ptrs = NULL; | |
100 | heap->len = 0; | |
101 | heap->alloc_len = 0; | |
102 | heap->gt = gt; | |
103 | /* | |
104 | * Minimum size allocated is 1 entry to ensure memory allocation | |
105 | * never fails within heap_replace_max. | |
106 | */ | |
107 | return heap_grow(heap, max_t(size_t, 1, alloc_len)); | |
108 | } | |
109 | ||
110 | void heap_free(struct ptr_heap *heap) | |
111 | { | |
112 | free(heap->ptrs); | |
113 | } | |
114 | ||
115 | static void heapify(struct ptr_heap *heap, size_t i) | |
116 | { | |
117 | void **ptrs = heap->ptrs; | |
118 | size_t l, r, largest; | |
119 | ||
120 | for (;;) { | |
eacd552c MD |
121 | void *tmp; |
122 | ||
1eb0c69c MD |
123 | l = left(i); |
124 | r = right(i); | |
eacd552c | 125 | if (l < heap->len && heap->gt(ptrs[l], ptrs[i])) |
1eb0c69c MD |
126 | largest = l; |
127 | else | |
128 | largest = i; | |
eacd552c | 129 | if (r < heap->len && heap->gt(ptrs[r], ptrs[largest])) |
1eb0c69c | 130 | largest = r; |
eacd552c | 131 | if (largest == i) |
1eb0c69c | 132 | break; |
eacd552c MD |
133 | tmp = ptrs[i]; |
134 | ptrs[i] = ptrs[largest]; | |
135 | ptrs[largest] = tmp; | |
136 | i = largest; | |
1eb0c69c | 137 | } |
eacd552c | 138 | check_heap(heap); |
1eb0c69c MD |
139 | } |
140 | ||
141 | void *heap_replace_max(struct ptr_heap *heap, void *p) | |
142 | { | |
143 | void *res; | |
1eb0c69c MD |
144 | |
145 | if (!heap->len) { | |
146 | (void) heap_set_len(heap, 1); | |
557255e5 | 147 | heap->ptrs[0] = p; |
eacd552c | 148 | check_heap(heap); |
1eb0c69c MD |
149 | return NULL; |
150 | } | |
151 | ||
152 | /* Replace the current max and heapify */ | |
557255e5 MD |
153 | res = heap->ptrs[0]; |
154 | heap->ptrs[0] = p; | |
1eb0c69c MD |
155 | heapify(heap, 0); |
156 | return res; | |
157 | } | |
158 | ||
159 | int heap_insert(struct ptr_heap *heap, void *p) | |
160 | { | |
557255e5 MD |
161 | void **ptrs; |
162 | size_t pos; | |
1eb0c69c MD |
163 | int ret; |
164 | ||
165 | ret = heap_set_len(heap, heap->len + 1); | |
166 | if (ret) | |
167 | return ret; | |
557255e5 | 168 | ptrs = heap->ptrs; |
557255e5 | 169 | pos = heap->len - 1; |
eacd552c MD |
170 | while (pos > 0 && heap->gt(p, ptrs[parent(pos)])) { |
171 | /* Move parent down until we find the right spot */ | |
172 | ptrs[pos] = ptrs[parent(pos)]; | |
173 | pos = parent(pos); | |
557255e5 | 174 | } |
eacd552c MD |
175 | ptrs[pos] = p; |
176 | check_heap(heap); | |
1eb0c69c MD |
177 | return 0; |
178 | } | |
179 | ||
180 | void *heap_remove(struct ptr_heap *heap) | |
181 | { | |
1eb0c69c MD |
182 | switch (heap->len) { |
183 | case 0: | |
184 | return NULL; | |
185 | case 1: | |
186 | (void) heap_set_len(heap, 0); | |
557255e5 | 187 | return heap->ptrs[0]; |
1eb0c69c MD |
188 | } |
189 | /* Shrink, replace the current max by previous last entry and heapify */ | |
190 | heap_set_len(heap, heap->len - 1); | |
eacd552c MD |
191 | /* len changed. previous last entry is at heap->len */ |
192 | return heap_replace_max(heap, heap->ptrs[heap->len]); | |
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); | |
eacd552c | 206 | check_heap(heap); |
557255e5 | 207 | return heap->ptrs[0]; |
1eb0c69c MD |
208 | } |
209 | /* Replace p with previous last entry and heapify. */ | |
210 | heap_set_len(heap, heap->len - 1); | |
eacd552c MD |
211 | /* len changed. previous last entry is at heap->len */ |
212 | heap->ptrs[pos] = heap->ptrs[heap->len]; | |
1eb0c69c MD |
213 | heapify(heap, pos); |
214 | return p; | |
215 | } |