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  * 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
  22 #include <linux/gfp.h>
  23
  24 struct ptr_heap {
  25         size_t len, alloc_len;
  26         void **ptrs;
  27         int (*gt)(void *a, void *b);
  28         gfp_t gfpmask;
  29 };
  30
  31 /**
  32  * 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 *heap_maximum(const struct ptr_heap *heap)
  39 {
  40         return heap->len ? heap->ptrs[0] : NULL;
  41 }
  42
  43 /**
  44  * heap_init - initialize the heap
  45  * @heap: the heap to initialize
  46  * @alloc_len: number of elements initially allocated
  47  * @gfp: allocation flags
  48  * @gt: function to compare the elements
  49  *
  50  * Returns -ENOMEM if out of memory.
  51  */
  52 extern int heap_init(struct ptr_heap *heap,
  53                      size_t alloc_len, gfp_t gfpmask,
  54                      int gt(void *a, void *b));
  55
  56 /**
  57  * heap_free - free the heap
  58  * @heap: the heap to free
  59  */
  60 extern void heap_free(struct ptr_heap *heap);
  61
  62 /**
  63  * heap_insert - insert an element into the heap
  64  * @heap: the heap to be operated on
  65  * @p: the element to add
  66  *
  67  * Insert an element into the heap.
  68  *
  69  * Returns -ENOMEM if out of memory.
  70  */
  71 extern int heap_insert(struct ptr_heap *heap, void *p);
  72
  73 /**
  74  * heap_remove - remove the largest element from the heap
  75  * @heap: the heap to be operated on
  76  *
  77  * Returns the largest element in the heap. It removes this element from the
  78  * heap. Returns NULL if the heap is empty.
  79  */
  80 extern void *heap_remove(struct ptr_heap *heap);
  81
  82 /**
  83  * heap_cherrypick - remove a given element from the heap
  84  * @heap: the heap to be operated on
  85  * @p: the element
  86  *
  87  * Remove the given element from the heap. Return the element if present, else
  88  * return NULL. This algorithm has a complexity of O(n), which is higher than
  89  * O(log(n)) provided by the rest of this API.
  90  */
  91 extern void *heap_cherrypick(struct ptr_heap *heap, void *p);
  92
  93 /**
  94  * heap_replace_max - replace the the largest element from the heap
  95  * @heap: the heap to be operated on
  96  * @p: the pointer to be inserted as topmost element replacement
  97  *
  98  * Returns the largest element in the heap. It removes this element from the
  99  * heap. The heap is rebalanced only once after the insertion. Returns NULL if
 100  * the heap is empty.
 101  *
 102  * This is the equivalent of calling heap_remove() and then heap_insert(), but
 103  * it only rebalances the heap once. It never allocates memory.
 104  */
 105 extern void *heap_replace_max(struct ptr_heap *heap, void *p);
 106
 107 #endif /* _LTTNG_PRIO_HEAP_H */