| 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 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 20 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 21 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| 22 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 23 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 24 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
| 25 | * SOFTWARE. |
| 26 | */ |
| 27 | |
| 28 | #include <babeltrace/prio_heap.h> |
| 29 | #include <babeltrace/babeltrace-internal.h> |
| 30 | #include <errno.h> |
| 31 | #include <stdlib.h> |
| 32 | #include <string.h> |
| 33 | #include <assert.h> |
| 34 | |
| 35 | #ifndef max_t |
| 36 | #define max_t(type, a, b) \ |
| 37 | ((type) (a) > (type) (b) ? (type) (a) : (type) (b)) |
| 38 | #endif |
| 39 | |
| 40 | #ifdef DEBUG_HEAP |
| 41 | void check_heap(const struct ptr_heap *heap) |
| 42 | { |
| 43 | size_t i; |
| 44 | |
| 45 | if (!heap->len) |
| 46 | return; |
| 47 | |
| 48 | for (i = 1; i < heap->len; i++) |
| 49 | assert(!heap->gt(heap->ptrs[i], heap->ptrs[0])); |
| 50 | } |
| 51 | #endif |
| 52 | |
| 53 | static |
| 54 | size_t parent(size_t i) |
| 55 | { |
| 56 | return (i - 1) >> 1; |
| 57 | } |
| 58 | |
| 59 | static |
| 60 | size_t left(size_t i) |
| 61 | { |
| 62 | return (i << 1) + 1; |
| 63 | } |
| 64 | |
| 65 | static |
| 66 | size_t right(size_t i) |
| 67 | { |
| 68 | return (i << 1) + 2; |
| 69 | } |
| 70 | |
| 71 | /* |
| 72 | * Copy of heap->ptrs pointer is invalid after heap_grow. |
| 73 | */ |
| 74 | static |
| 75 | int heap_grow(struct ptr_heap *heap, size_t new_len) |
| 76 | { |
| 77 | void **new_ptrs; |
| 78 | |
| 79 | if (likely(heap->alloc_len >= new_len)) |
| 80 | return 0; |
| 81 | |
| 82 | heap->alloc_len = max_t(size_t, new_len, heap->alloc_len << 1); |
| 83 | new_ptrs = calloc(heap->alloc_len, sizeof(void *)); |
| 84 | if (unlikely(!new_ptrs)) |
| 85 | return -ENOMEM; |
| 86 | if (likely(heap->ptrs)) |
| 87 | memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *)); |
| 88 | free(heap->ptrs); |
| 89 | heap->ptrs = new_ptrs; |
| 90 | return 0; |
| 91 | } |
| 92 | |
| 93 | static |
| 94 | int heap_set_len(struct ptr_heap *heap, size_t new_len) |
| 95 | { |
| 96 | int ret; |
| 97 | |
| 98 | ret = heap_grow(heap, new_len); |
| 99 | if (unlikely(ret)) |
| 100 | return ret; |
| 101 | heap->len = new_len; |
| 102 | return 0; |
| 103 | } |
| 104 | |
| 105 | int bt_heap_init(struct ptr_heap *heap, size_t alloc_len, |
| 106 | int gt(void *a, void *b)) |
| 107 | { |
| 108 | heap->ptrs = NULL; |
| 109 | heap->len = 0; |
| 110 | heap->alloc_len = 0; |
| 111 | heap->gt = gt; |
| 112 | /* |
| 113 | * Minimum size allocated is 1 entry to ensure memory allocation |
| 114 | * never fails within bt_heap_replace_max. |
| 115 | */ |
| 116 | return heap_grow(heap, max_t(size_t, 1, alloc_len)); |
| 117 | } |
| 118 | |
| 119 | void bt_heap_free(struct ptr_heap *heap) |
| 120 | { |
| 121 | free(heap->ptrs); |
| 122 | } |
| 123 | |
| 124 | static void heapify(struct ptr_heap *heap, size_t i) |
| 125 | { |
| 126 | void **ptrs = heap->ptrs; |
| 127 | size_t l, r, largest; |
| 128 | |
| 129 | for (;;) { |
| 130 | void *tmp; |
| 131 | |
| 132 | l = left(i); |
| 133 | r = right(i); |
| 134 | if (l < heap->len && heap->gt(ptrs[l], ptrs[i])) |
| 135 | largest = l; |
| 136 | else |
| 137 | largest = i; |
| 138 | if (r < heap->len && heap->gt(ptrs[r], ptrs[largest])) |
| 139 | largest = r; |
| 140 | if (unlikely(largest == i)) |
| 141 | break; |
| 142 | tmp = ptrs[i]; |
| 143 | ptrs[i] = ptrs[largest]; |
| 144 | ptrs[largest] = tmp; |
| 145 | i = largest; |
| 146 | } |
| 147 | check_heap(heap); |
| 148 | } |
| 149 | |
| 150 | void *bt_heap_replace_max(struct ptr_heap *heap, void *p) |
| 151 | { |
| 152 | void *res; |
| 153 | |
| 154 | if (unlikely(!heap->len)) { |
| 155 | (void) heap_set_len(heap, 1); |
| 156 | heap->ptrs[0] = p; |
| 157 | check_heap(heap); |
| 158 | return NULL; |
| 159 | } |
| 160 | |
| 161 | /* Replace the current max and heapify */ |
| 162 | res = heap->ptrs[0]; |
| 163 | heap->ptrs[0] = p; |
| 164 | heapify(heap, 0); |
| 165 | return res; |
| 166 | } |
| 167 | |
| 168 | int bt_heap_insert(struct ptr_heap *heap, void *p) |
| 169 | { |
| 170 | void **ptrs; |
| 171 | size_t pos; |
| 172 | int ret; |
| 173 | |
| 174 | ret = heap_set_len(heap, heap->len + 1); |
| 175 | if (unlikely(ret)) |
| 176 | return ret; |
| 177 | ptrs = heap->ptrs; |
| 178 | pos = heap->len - 1; |
| 179 | while (pos > 0 && heap->gt(p, ptrs[parent(pos)])) { |
| 180 | /* Move parent down until we find the right spot */ |
| 181 | ptrs[pos] = ptrs[parent(pos)]; |
| 182 | pos = parent(pos); |
| 183 | } |
| 184 | ptrs[pos] = p; |
| 185 | check_heap(heap); |
| 186 | return 0; |
| 187 | } |
| 188 | |
| 189 | void *bt_heap_remove(struct ptr_heap *heap) |
| 190 | { |
| 191 | switch (heap->len) { |
| 192 | case 0: |
| 193 | return NULL; |
| 194 | case 1: |
| 195 | (void) heap_set_len(heap, 0); |
| 196 | return heap->ptrs[0]; |
| 197 | } |
| 198 | /* Shrink, replace the current max by previous last entry and heapify */ |
| 199 | heap_set_len(heap, heap->len - 1); |
| 200 | /* len changed. previous last entry is at heap->len */ |
| 201 | return bt_heap_replace_max(heap, heap->ptrs[heap->len]); |
| 202 | } |
| 203 | |
| 204 | void *bt_heap_cherrypick(struct ptr_heap *heap, void *p) |
| 205 | { |
| 206 | size_t pos, len = heap->len; |
| 207 | |
| 208 | for (pos = 0; pos < len; pos++) |
| 209 | if (unlikely(heap->ptrs[pos] == p)) |
| 210 | goto found; |
| 211 | return NULL; |
| 212 | found: |
| 213 | if (unlikely(heap->len == 1)) { |
| 214 | (void) heap_set_len(heap, 0); |
| 215 | check_heap(heap); |
| 216 | return heap->ptrs[0]; |
| 217 | } |
| 218 | /* Replace p with previous last entry and heapify. */ |
| 219 | heap_set_len(heap, heap->len - 1); |
| 220 | /* len changed. previous last entry is at heap->len */ |
| 221 | heap->ptrs[pos] = heap->ptrs[heap->len]; |
| 222 | heapify(heap, pos); |
| 223 | return p; |
| 224 | } |
| 225 | |
| 226 | int bt_heap_copy(struct ptr_heap *dst, struct ptr_heap *src) |
| 227 | { |
| 228 | int ret; |
| 229 | |
| 230 | ret = bt_heap_init(dst, src->alloc_len, src->gt); |
| 231 | if (ret < 0) |
| 232 | goto end; |
| 233 | |
| 234 | ret = heap_set_len(dst, src->len); |
| 235 | if (ret < 0) |
| 236 | goto end; |
| 237 | |
| 238 | memcpy(dst->ptrs, src->ptrs, src->len * sizeof(void *)); |
| 239 | |
| 240 | end: |
| 241 | return ret; |
| 242 | } |