| 1 | /* |
| 2 | * LICENSING: this file is copied from the Linux kernel. We should therefore |
| 3 | * assume a GPLv2 license for the code that comes from the Linux mainline. |
| 4 | */ |
| 5 | |
| 6 | #ifndef _LINUX_PRIO_HEAP_H |
| 7 | #define _LINUX_PRIO_HEAP_H |
| 8 | |
| 9 | /* |
| 10 | * Static-sized priority heap containing pointers. Based on CLR, chapter 7. |
| 11 | */ |
| 12 | |
| 13 | #include <linux/gfp.h> |
| 14 | |
| 15 | /** |
| 16 | * struct ptr_heap - simple static-sized priority heap |
| 17 | * @ptrs - pointer to data area |
| 18 | * @max - max number of elements that can be stored in @ptrs |
| 19 | * @size - current number of valid elements in @ptrs (in the range 0..@size-1 |
| 20 | * @gt: comparison operator, which should implement "greater than" |
| 21 | */ |
| 22 | struct ptr_heap { |
| 23 | void **ptrs; |
| 24 | int max; |
| 25 | int size; |
| 26 | int (*gt)(void *, void *); |
| 27 | }; |
| 28 | |
| 29 | /** |
| 30 | * heap_maximum - return the largest element in the heap |
| 31 | * @heap: the heap to be operated on |
| 32 | * |
| 33 | * Returns the largest element in the heap, without performing any modification |
| 34 | * to the heap structure. Returns NULL if the heap is empty. |
| 35 | */ |
| 36 | static inline void *heap_maximum(const struct ptr_heap *heap) |
| 37 | { |
| 38 | return heap->size ? heap->ptrs[0] : NULL; |
| 39 | } |
| 40 | |
| 41 | /** |
| 42 | * heap_init - initialize an empty heap with a given memory size |
| 43 | * @heap: the heap structure to be initialized |
| 44 | * @size: amount of memory to use in bytes |
| 45 | * @gfp_mask: mask to pass to kmalloc() |
| 46 | * @gt: comparison operator, which should implement "greater than" |
| 47 | */ |
| 48 | extern int heap_init(struct ptr_heap *heap, size_t size, gfp_t gfp_mask, |
| 49 | int (*gt)(void *, void *)); |
| 50 | |
| 51 | /** |
| 52 | * heap_free - release a heap's storage |
| 53 | * @heap: the heap structure whose data should be released |
| 54 | */ |
| 55 | void heap_free(struct ptr_heap *heap); |
| 56 | |
| 57 | /** |
| 58 | * heap_insert - insert a value into the heap and return any overflowed value |
| 59 | * @heap: the heap to be operated on |
| 60 | * @p: the pointer to be inserted |
| 61 | * |
| 62 | * Attempts to insert the given value into the priority heap. If the |
| 63 | * heap is full prior to the insertion, then the resulting heap will |
| 64 | * consist of the smallest @max elements of the original heap and the |
| 65 | * new element; the greatest element will be removed from the heap and |
| 66 | * returned. Note that the returned element will be the new element |
| 67 | * (i.e. no change to the heap) if the new element is greater than all |
| 68 | * elements currently in the heap. |
| 69 | */ |
| 70 | extern void *heap_insert(struct ptr_heap *heap, void *p); |
| 71 | |
| 72 | /** |
| 73 | * heap_remove - remove the largest element from the heap |
| 74 | * @heap: the heap to be operated on |
| 75 | * |
| 76 | * Returns the largest element in the heap. It removes this element from the |
| 77 | * heap. Returns NULL if the heap is empty. |
| 78 | */ |
| 79 | extern void *heap_remove(struct ptr_heap *heap); |
| 80 | |
| 81 | /** |
| 82 | * heap_cherrypick - remove a given element from the heap |
| 83 | * @heap: the heap to be operated on |
| 84 | * @p: the element |
| 85 | * |
| 86 | * Remove the given element from the heap. Return the element if present, else |
| 87 | * return NULL. This algorithm has a complexity of O(n), which is higher than |
| 88 | * O(log(n)) provided by the rest of this API. |
| 89 | */ |
| 90 | extern void *heap_cherrypick(struct ptr_heap *heap, void *p); |
| 91 | |
| 92 | /** |
| 93 | * heap_replace_max - replace the the largest element from the heap |
| 94 | * @heap: the heap to be operated on |
| 95 | * @p: the pointer to be inserted as topmost element replacement |
| 96 | * |
| 97 | * Returns the largest element in the heap. It removes this element from the |
| 98 | * heap. The heap is rebalanced only once after the insertion. Returns NULL if |
| 99 | * the heap is empty. |
| 100 | * |
| 101 | * This is the equivalent of calling heap_remove() and then heap_insert(), but |
| 102 | * it only rebalances the heap once. |
| 103 | */ |
| 104 | extern void *heap_replace_max(struct ptr_heap *heap, void *p); |
| 105 | |
| 106 | #endif /* _LINUX_PRIO_HEAP_H */ |