lib/prio_heap/prio_heap.h

   1 #ifndef _LTTNG_PRIO_HEAP_H
   2 #define _LTTNG_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 /*
  24  * TODO:
  25  * implement struct ptr_head, heap_init, heap_free, heap_insert.
  26  */
  27
  28 /**
  29  * heap_maximum - return the largest element in the heap
  30  * @heap: the heap to be operated on
  31  *
  32  * Returns the largest element in the heap, without performing any modification
  33  * to the heap structure. Returns NULL if the heap is empty.
  34  */
  35 static inline void *heap_maximum(const struct ptr_heap *heap)
  36 {
  37         return heap->size ? heap->ptrs[0] : NULL;
  38 }
  39
  40
  41 /**
  42  * heap_remove - remove the largest element from the heap
  43  * @heap: the heap to be operated on
  44  *
  45  * Returns the largest element in the heap. It removes this element from the
  46  * heap. Returns NULL if the heap is empty.
  47  */
  48 extern void *heap_remove(struct ptr_heap *heap);
  49
  50 /**
  51  * heap_cherrypick - remove a given element from the heap
  52  * @heap: the heap to be operated on
  53  * @p: the element
  54  *
  55  * Remove the given element from the heap. Return the element if present, else
  56  * return NULL. This algorithm has a complexity of O(n), which is higher than
  57  * O(log(n)) provided by the rest of this API.
  58  */
  59 extern void *heap_cherrypick(struct ptr_heap *heap, void *p);
  60
  61 /**
  62  * heap_replace_max - replace the the largest element from the heap
  63  * @heap: the heap to be operated on
  64  * @p: the pointer to be inserted as topmost element replacement
  65  *
  66  * Returns the largest element in the heap. It removes this element from the
  67  * heap. The heap is rebalanced only once after the insertion. Returns NULL if
  68  * the heap is empty.
  69  *
  70  * This is the equivalent of calling heap_remove() and then heap_insert(), but
  71  * it only rebalances the heap once.
  72  */
  73 extern void *heap_replace_max(struct ptr_heap *heap, void *p);
  74
  75 #endif /* _LTTNG_PRIO_HEAP_H */