lib/prio_heap/lttng_prio_heap.h

   1 #ifndef _LTTNG_PRIO_HEAP_H
   2 #define _LTTNG_PRIO_HEAP_H
   3
   4 /*
   5  * lttng_prio_heap.h
   6  *
   7  * Priority heap containing pointers. Based on CLRS, chapter 6.
   8  *
   9  * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * Permission is hereby granted, free of charge, to any person obtaining a copy
  12  * of this software and associated documentation files (the "Software"), to deal
  13  * in the Software without restriction, including without limitation the rights
  14  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15  * copies of the Software, and to permit persons to whom the Software is
  16  * furnished to do so, subject to the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be included in
  19  * all copies or substantial portions of the Software.
  20  *
  21  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  22  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  23  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  24  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  25  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  26  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  27  * SOFTWARE.
  28  */
  29
  30 #include <linux/gfp.h>
  31
  32 struct lttng_ptr_heap {
  33         size_t len, alloc_len;
  34         void **ptrs;
  35         int (*gt)(void *a, void *b);
  36         gfp_t gfpmask;
  37 };
  38
  39 #ifdef DEBUG_HEAP
  40 void lttng_check_heap(const struct lttng_ptr_heap *heap);
  41 #else
  42 static inline
  43 void lttng_check_heap(const struct lttng_ptr_heap *heap)
  44 {
  45 }
  46 #endif
  47
  48 /**
  49  * lttng_heap_maximum - return the largest element in the heap
  50  * @heap: the heap to be operated on
  51  *
  52  * Returns the largest element in the heap, without performing any modification
  53  * to the heap structure. Returns NULL if the heap is empty.
  54  */
  55 static inline void *lttng_heap_maximum(const struct lttng_ptr_heap *heap)
  56 {
  57         lttng_check_heap(heap);
  58         return heap->len ? heap->ptrs[0] : NULL;
  59 }
  60
  61 /**
  62  * lttng_heap_init - initialize the heap
  63  * @heap: the heap to initialize
  64  * @alloc_len: number of elements initially allocated
  65  * @gfp: allocation flags
  66  * @gt: function to compare the elements
  67  *
  68  * Returns -ENOMEM if out of memory.
  69  */
  70 extern int lttng_heap_init(struct lttng_ptr_heap *heap,
  71                      size_t alloc_len, gfp_t gfpmask,
  72                      int gt(void *a, void *b));
  73
  74 /**
  75  * lttng_heap_free - free the heap
  76  * @heap: the heap to free
  77  */
  78 extern void lttng_heap_free(struct lttng_ptr_heap *heap);
  79
  80 /**
  81  * lttng_heap_insert - insert an element into the heap
  82  * @heap: the heap to be operated on
  83  * @p: the element to add
  84  *
  85  * Insert an element into the heap.
  86  *
  87  * Returns -ENOMEM if out of memory.
  88  */
  89 extern int lttng_heap_insert(struct lttng_ptr_heap *heap, void *p);
  90
  91 /**
  92  * lttng_heap_remove - remove the largest element from the heap
  93  * @heap: the heap to be operated on
  94  *
  95  * Returns the largest element in the heap. It removes this element from the
  96  * heap. Returns NULL if the heap is empty.
  97  */
  98 extern void *lttng_heap_remove(struct lttng_ptr_heap *heap);
  99
 100 /**
 101  * lttng_heap_cherrypick - remove a given element from the heap
 102  * @heap: the heap to be operated on
 103  * @p: the element
 104  *
 105  * Remove the given element from the heap. Return the element if present, else
 106  * return NULL. This algorithm has a complexity of O(n), which is higher than
 107  * O(log(n)) provided by the rest of this API.
 108  */
 109 extern void *lttng_heap_cherrypick(struct lttng_ptr_heap *heap, void *p);
 110
 111 /**
 112  * lttng_heap_replace_max - replace the the largest element from the heap
 113  * @heap: the heap to be operated on
 114  * @p: the pointer to be inserted as topmost element replacement
 115  *
 116  * Returns the largest element in the heap. It removes this element from the
 117  * heap. The heap is rebalanced only once after the insertion. Returns NULL if
 118  * the heap is empty.
 119  *
 120  * This is the equivalent of calling heap_remove() and then heap_insert(), but
 121  * it only rebalances the heap once. It never allocates memory.
 122  */
 123 extern void *lttng_heap_replace_max(struct lttng_ptr_heap *heap, void *p);
 124
 125 #endif /* _LTTNG_PRIO_HEAP_H */