| 1 | #ifndef _BABELTRACE_PRIO_HEAP_H |
| 2 | #define _BABELTRACE_PRIO_HEAP_H |
| 3 | |
| 4 | /* |
| 5 | * prio_heap.h |
| 6 | * |
| 7 | * Static-sized priority heap containing pointers. Based on CLRS, |
| 8 | * chapter 6. |
| 9 | * |
| 10 | * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 11 | * |
| 12 | * Permission is hereby granted, free of charge, to any person obtaining a copy |
| 13 | * of this software and associated documentation files (the "Software"), to deal |
| 14 | * in the Software without restriction, including without limitation the rights |
| 15 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 16 | * copies of the Software, and to permit persons to whom the Software is |
| 17 | * furnished to do so, subject to the following conditions: |
| 18 | * |
| 19 | * The above copyright notice and this permission notice shall be included in |
| 20 | * all copies or substantial portions of the Software. |
| 21 | */ |
| 22 | |
| 23 | #include <unistd.h> |
| 24 | |
| 25 | struct ptr_heap { |
| 26 | size_t len, alloc_len; |
| 27 | void **ptrs; |
| 28 | int (*gt)(void *a, void *b); |
| 29 | }; |
| 30 | |
| 31 | #ifdef DEBUG_HEAP |
| 32 | void check_heap(const struct ptr_heap *heap); |
| 33 | #else |
| 34 | static inline |
| 35 | void check_heap(const struct ptr_heap *heap) |
| 36 | { |
| 37 | } |
| 38 | #endif |
| 39 | |
| 40 | /** |
| 41 | * heap_maximum - return the largest element in the heap |
| 42 | * @heap: the heap to be operated on |
| 43 | * |
| 44 | * Returns the largest element in the heap, without performing any modification |
| 45 | * to the heap structure. Returns NULL if the heap is empty. |
| 46 | */ |
| 47 | static inline void *heap_maximum(const struct ptr_heap *heap) |
| 48 | { |
| 49 | check_heap(heap); |
| 50 | return heap->len ? heap->ptrs[0] : NULL; |
| 51 | } |
| 52 | |
| 53 | /** |
| 54 | * heap_init - initialize the heap |
| 55 | * @heap: the heap to initialize |
| 56 | * @alloc_len: number of elements initially allocated |
| 57 | * @gt: function to compare the elements |
| 58 | * |
| 59 | * Returns -ENOMEM if out of memory. |
| 60 | */ |
| 61 | extern int heap_init(struct ptr_heap *heap, |
| 62 | size_t alloc_len, |
| 63 | int gt(void *a, void *b)); |
| 64 | |
| 65 | /** |
| 66 | * heap_free - free the heap |
| 67 | * @heap: the heap to free |
| 68 | */ |
| 69 | extern void heap_free(struct ptr_heap *heap); |
| 70 | |
| 71 | /** |
| 72 | * heap_insert - insert an element into the heap |
| 73 | * @heap: the heap to be operated on |
| 74 | * @p: the element to add |
| 75 | * |
| 76 | * Insert an element into the heap. |
| 77 | * |
| 78 | * Returns -ENOMEM if out of memory. |
| 79 | */ |
| 80 | extern int heap_insert(struct ptr_heap *heap, void *p); |
| 81 | |
| 82 | /** |
| 83 | * heap_remove - remove the largest element from the heap |
| 84 | * @heap: the heap to be operated on |
| 85 | * |
| 86 | * Returns the largest element in the heap. It removes this element from the |
| 87 | * heap. Returns NULL if the heap is empty. |
| 88 | */ |
| 89 | extern void *heap_remove(struct ptr_heap *heap); |
| 90 | |
| 91 | /** |
| 92 | * heap_cherrypick - remove a given element from the heap |
| 93 | * @heap: the heap to be operated on |
| 94 | * @p: the element |
| 95 | * |
| 96 | * Remove the given element from the heap. Return the element if present, else |
| 97 | * return NULL. This algorithm has a complexity of O(n), which is higher than |
| 98 | * O(log(n)) provided by the rest of this API. |
| 99 | */ |
| 100 | extern void *heap_cherrypick(struct ptr_heap *heap, void *p); |
| 101 | |
| 102 | /** |
| 103 | * heap_replace_max - replace the the largest element from the heap |
| 104 | * @heap: the heap to be operated on |
| 105 | * @p: the pointer to be inserted as topmost element replacement |
| 106 | * |
| 107 | * Returns the largest element in the heap. It removes this element from the |
| 108 | * heap. The heap is rebalanced only once after the insertion. Returns NULL if |
| 109 | * the heap is empty. |
| 110 | * |
| 111 | * This is the equivalent of calling heap_remove() and then heap_insert(), but |
| 112 | * it only rebalances the heap once. It never allocates memory. |
| 113 | */ |
| 114 | extern void *heap_replace_max(struct ptr_heap *heap, void *p); |
| 115 | |
| 116 | #endif /* _BABELTRACE_PRIO_HEAP_H */ |