| 1 | /* |
| 2 | * SPDX-License-Identifier: MIT |
| 3 | * |
| 4 | * Copyright 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | * |
| 6 | * Static-sized priority heap containing pointers. Based on CLRS, |
| 7 | * chapter 6. |
| 8 | */ |
| 9 | |
| 10 | #include "common/macros.h" |
| 11 | #include "common/assert.h" |
| 12 | #include <errno.h> |
| 13 | #include <stdlib.h> |
| 14 | #include <string.h> |
| 15 | |
| 16 | #include "common/prio-heap.h" |
| 17 | |
| 18 | #ifdef DEBUG_HEAP |
| 19 | void check_heap(const struct ptr_heap *heap) |
| 20 | { |
| 21 | size_t i; |
| 22 | |
| 23 | if (!heap->len) |
| 24 | return; |
| 25 | |
| 26 | for (i = 1; i < heap->len; i++) |
| 27 | BT_ASSERT_DBG(!heap->gt(heap->ptrs[i], heap->ptrs[0])); |
| 28 | } |
| 29 | #endif |
| 30 | |
| 31 | static |
| 32 | size_t parent(size_t i) |
| 33 | { |
| 34 | return (i - 1) >> 1; |
| 35 | } |
| 36 | |
| 37 | static |
| 38 | size_t left(size_t i) |
| 39 | { |
| 40 | return (i << 1) + 1; |
| 41 | } |
| 42 | |
| 43 | static |
| 44 | size_t right(size_t i) |
| 45 | { |
| 46 | return (i << 1) + 2; |
| 47 | } |
| 48 | |
| 49 | /* |
| 50 | * Copy of heap->ptrs pointer is invalid after heap_grow. |
| 51 | */ |
| 52 | static |
| 53 | int heap_grow(struct ptr_heap *heap, size_t new_len) |
| 54 | { |
| 55 | void **new_ptrs; |
| 56 | |
| 57 | if (G_LIKELY(heap->alloc_len >= new_len)) |
| 58 | return 0; |
| 59 | |
| 60 | heap->alloc_len = bt_max_t(size_t, new_len, heap->alloc_len << 1); |
| 61 | new_ptrs = calloc(heap->alloc_len, sizeof(void *)); |
| 62 | if (G_UNLIKELY(!new_ptrs)) |
| 63 | return -ENOMEM; |
| 64 | if (G_LIKELY(heap->ptrs)) |
| 65 | memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *)); |
| 66 | free(heap->ptrs); |
| 67 | heap->ptrs = new_ptrs; |
| 68 | return 0; |
| 69 | } |
| 70 | |
| 71 | static |
| 72 | int heap_set_len(struct ptr_heap *heap, size_t new_len) |
| 73 | { |
| 74 | int ret; |
| 75 | |
| 76 | ret = heap_grow(heap, new_len); |
| 77 | if (G_UNLIKELY(ret)) |
| 78 | return ret; |
| 79 | heap->len = new_len; |
| 80 | return 0; |
| 81 | } |
| 82 | |
| 83 | int bt_heap_init(struct ptr_heap *heap, size_t alloc_len, |
| 84 | int gt(void *a, void *b)) |
| 85 | { |
| 86 | heap->ptrs = NULL; |
| 87 | heap->len = 0; |
| 88 | heap->alloc_len = 0; |
| 89 | heap->gt = gt; |
| 90 | /* |
| 91 | * Minimum size allocated is 1 entry to ensure memory allocation |
| 92 | * never fails within bt_heap_replace_max. |
| 93 | */ |
| 94 | return heap_grow(heap, bt_max_t(size_t, 1, alloc_len)); |
| 95 | } |
| 96 | |
| 97 | void bt_heap_free(struct ptr_heap *heap) |
| 98 | { |
| 99 | free(heap->ptrs); |
| 100 | } |
| 101 | |
| 102 | static void heapify(struct ptr_heap *heap, size_t i) |
| 103 | { |
| 104 | void **ptrs = heap->ptrs; |
| 105 | size_t l, r, largest; |
| 106 | |
| 107 | for (;;) { |
| 108 | void *tmp; |
| 109 | |
| 110 | l = left(i); |
| 111 | r = right(i); |
| 112 | if (l < heap->len && heap->gt(ptrs[l], ptrs[i])) |
| 113 | largest = l; |
| 114 | else |
| 115 | largest = i; |
| 116 | if (r < heap->len && heap->gt(ptrs[r], ptrs[largest])) |
| 117 | largest = r; |
| 118 | if (G_UNLIKELY(largest == i)) |
| 119 | break; |
| 120 | tmp = ptrs[i]; |
| 121 | ptrs[i] = ptrs[largest]; |
| 122 | ptrs[largest] = tmp; |
| 123 | i = largest; |
| 124 | } |
| 125 | check_heap(heap); |
| 126 | } |
| 127 | |
| 128 | void *bt_heap_replace_max(struct ptr_heap *heap, void *p) |
| 129 | { |
| 130 | void *res; |
| 131 | |
| 132 | if (G_UNLIKELY(!heap->len)) { |
| 133 | (void) heap_set_len(heap, 1); |
| 134 | heap->ptrs[0] = p; |
| 135 | check_heap(heap); |
| 136 | return NULL; |
| 137 | } |
| 138 | |
| 139 | /* Replace the current max and heapify */ |
| 140 | res = heap->ptrs[0]; |
| 141 | heap->ptrs[0] = p; |
| 142 | heapify(heap, 0); |
| 143 | return res; |
| 144 | } |
| 145 | |
| 146 | int bt_heap_insert(struct ptr_heap *heap, void *p) |
| 147 | { |
| 148 | void **ptrs; |
| 149 | size_t pos; |
| 150 | int ret; |
| 151 | |
| 152 | ret = heap_set_len(heap, heap->len + 1); |
| 153 | if (G_UNLIKELY(ret)) |
| 154 | return ret; |
| 155 | ptrs = heap->ptrs; |
| 156 | pos = heap->len - 1; |
| 157 | while (pos > 0 && heap->gt(p, ptrs[parent(pos)])) { |
| 158 | /* Move parent down until we find the right spot */ |
| 159 | ptrs[pos] = ptrs[parent(pos)]; |
| 160 | pos = parent(pos); |
| 161 | } |
| 162 | ptrs[pos] = p; |
| 163 | check_heap(heap); |
| 164 | return 0; |
| 165 | } |
| 166 | |
| 167 | void *bt_heap_remove(struct ptr_heap *heap) |
| 168 | { |
| 169 | switch (heap->len) { |
| 170 | case 0: |
| 171 | return NULL; |
| 172 | case 1: |
| 173 | (void) heap_set_len(heap, 0); |
| 174 | return heap->ptrs[0]; |
| 175 | } |
| 176 | /* Shrink, replace the current max by previous last entry and heapify */ |
| 177 | heap_set_len(heap, heap->len - 1); |
| 178 | /* len changed. previous last entry is at heap->len */ |
| 179 | return bt_heap_replace_max(heap, heap->ptrs[heap->len]); |
| 180 | } |
| 181 | |
| 182 | void *bt_heap_cherrypick(struct ptr_heap *heap, void *p) |
| 183 | { |
| 184 | size_t pos, len = heap->len; |
| 185 | |
| 186 | for (pos = 0; pos < len; pos++) |
| 187 | if (G_UNLIKELY(heap->ptrs[pos] == p)) |
| 188 | goto found; |
| 189 | return NULL; |
| 190 | found: |
| 191 | if (G_UNLIKELY(heap->len == 1)) { |
| 192 | (void) heap_set_len(heap, 0); |
| 193 | check_heap(heap); |
| 194 | return heap->ptrs[0]; |
| 195 | } |
| 196 | /* Replace p with previous last entry and heapify. */ |
| 197 | heap_set_len(heap, heap->len - 1); |
| 198 | /* len changed. previous last entry is at heap->len */ |
| 199 | heap->ptrs[pos] = heap->ptrs[heap->len]; |
| 200 | heapify(heap, pos); |
| 201 | return p; |
| 202 | } |
| 203 | |
| 204 | int bt_heap_copy(struct ptr_heap *dst, struct ptr_heap *src) |
| 205 | { |
| 206 | int ret; |
| 207 | |
| 208 | ret = bt_heap_init(dst, src->alloc_len, src->gt); |
| 209 | if (ret < 0) |
| 210 | goto end; |
| 211 | |
| 212 | ret = heap_set_len(dst, src->len); |
| 213 | if (ret < 0) |
| 214 | goto end; |
| 215 | |
| 216 | memcpy(dst->ptrs, src->ptrs, src->len * sizeof(void *)); |
| 217 | |
| 218 | end: |
| 219 | return ret; |
| 220 | } |