| 1 | /* SPDX-License-Identifier: MIT |
| 2 | * |
| 3 | * lttng/prio_heap.h |
| 4 | * |
| 5 | * Priority heap containing pointers. Based on CLRS, chapter 6. |
| 6 | * |
| 7 | * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 8 | */ |
| 9 | |
| 10 | #ifndef _LTTNG_PRIO_HEAP_H |
| 11 | #define _LTTNG_PRIO_HEAP_H |
| 12 | |
| 13 | #include <linux/gfp.h> |
| 14 | |
| 15 | struct lttng_ptr_heap { |
| 16 | size_t len, alloc_len; |
| 17 | void **ptrs; |
| 18 | int (*gt)(void *a, void *b); |
| 19 | gfp_t gfpmask; |
| 20 | }; |
| 21 | |
| 22 | #ifdef DEBUG_HEAP |
| 23 | void lttng_check_heap(const struct lttng_ptr_heap *heap); |
| 24 | #else |
| 25 | static inline |
| 26 | void lttng_check_heap(const struct lttng_ptr_heap *heap) |
| 27 | { |
| 28 | } |
| 29 | #endif |
| 30 | |
| 31 | /** |
| 32 | * lttng_heap_maximum - return the largest element in the heap |
| 33 | * @heap: the heap to be operated on |
| 34 | * |
| 35 | * Returns the largest element in the heap, without performing any modification |
| 36 | * to the heap structure. Returns NULL if the heap is empty. |
| 37 | */ |
| 38 | static inline void *lttng_heap_maximum(const struct lttng_ptr_heap *heap) |
| 39 | { |
| 40 | lttng_check_heap(heap); |
| 41 | return heap->len ? heap->ptrs[0] : NULL; |
| 42 | } |
| 43 | |
| 44 | /** |
| 45 | * lttng_heap_init - initialize the heap |
| 46 | * @heap: the heap to initialize |
| 47 | * @alloc_len: number of elements initially allocated |
| 48 | * @gfp: allocation flags |
| 49 | * @gt: function to compare the elements |
| 50 | * |
| 51 | * Returns -ENOMEM if out of memory. |
| 52 | */ |
| 53 | extern int lttng_heap_init(struct lttng_ptr_heap *heap, |
| 54 | size_t alloc_len, gfp_t gfpmask, |
| 55 | int gt(void *a, void *b)); |
| 56 | |
| 57 | /** |
| 58 | * lttng_heap_free - free the heap |
| 59 | * @heap: the heap to free |
| 60 | */ |
| 61 | extern void lttng_heap_free(struct lttng_ptr_heap *heap); |
| 62 | |
| 63 | /** |
| 64 | * lttng_heap_insert - insert an element into the heap |
| 65 | * @heap: the heap to be operated on |
| 66 | * @p: the element to add |
| 67 | * |
| 68 | * Insert an element into the heap. |
| 69 | * |
| 70 | * Returns -ENOMEM if out of memory. |
| 71 | */ |
| 72 | extern int lttng_heap_insert(struct lttng_ptr_heap *heap, void *p); |
| 73 | |
| 74 | /** |
| 75 | * lttng_heap_remove - remove the largest element from the heap |
| 76 | * @heap: the heap to be operated on |
| 77 | * |
| 78 | * Returns the largest element in the heap. It removes this element from the |
| 79 | * heap. Returns NULL if the heap is empty. |
| 80 | */ |
| 81 | extern void *lttng_heap_remove(struct lttng_ptr_heap *heap); |
| 82 | |
| 83 | /** |
| 84 | * lttng_heap_cherrypick - remove a given element from the heap |
| 85 | * @heap: the heap to be operated on |
| 86 | * @p: the element |
| 87 | * |
| 88 | * Remove the given element from the heap. Return the element if present, else |
| 89 | * return NULL. This algorithm has a complexity of O(n), which is higher than |
| 90 | * O(log(n)) provided by the rest of this API. |
| 91 | */ |
| 92 | extern void *lttng_heap_cherrypick(struct lttng_ptr_heap *heap, void *p); |
| 93 | |
| 94 | /** |
| 95 | * lttng_heap_replace_max - replace the the largest element from the heap |
| 96 | * @heap: the heap to be operated on |
| 97 | * @p: the pointer to be inserted as topmost element replacement |
| 98 | * |
| 99 | * Returns the largest element in the heap. It removes this element from the |
| 100 | * heap. The heap is rebalanced only once after the insertion. Returns NULL if |
| 101 | * the heap is empty. |
| 102 | * |
| 103 | * This is the equivalent of calling heap_remove() and then heap_insert(), but |
| 104 | * it only rebalances the heap once. It never allocates memory. |
| 105 | */ |
| 106 | extern void *lttng_heap_replace_max(struct lttng_ptr_heap *heap, void *p); |
| 107 | |
| 108 | #endif /* _LTTNG_PRIO_HEAP_H */ |