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 #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  * @gfp: allocation flags
  58  * @gt: function to compare the elements
  59  *
  60  * Returns -ENOMEM if out of memory.
  61  */
  62 extern int heap_init(struct ptr_heap *heap,
  63                      size_t alloc_len, gfp_t gfpmask,
  64                      int gt(void *a, void *b));
  65
  66 /**
  67  * heap_free - free the heap
  68  * @heap: the heap to free
  69  */
  70 extern void heap_free(struct ptr_heap *heap);
  71
  72 /**
  73  * heap_insert - insert an element into the heap
  74  * @heap: the heap to be operated on
  75  * @p: the element to add
  76  *
  77  * Insert an element into the heap.
  78  *
  79  * Returns -ENOMEM if out of memory.
  80  */
  81 extern int heap_insert(struct ptr_heap *heap, void *p);
  82
  83 /**
  84  * heap_remove - remove the largest element from the heap
  85  * @heap: the heap to be operated on
  86  *
  87  * Returns the largest element in the heap. It removes this element from the
  88  * heap. Returns NULL if the heap is empty.
  89  */
  90 extern void *heap_remove(struct ptr_heap *heap);
  91
  92 /**
  93  * heap_cherrypick - remove a given element from the heap
  94  * @heap: the heap to be operated on
  95  * @p: the element
  96  *
  97  * Remove the given element from the heap. Return the element if present, else
  98  * return NULL. This algorithm has a complexity of O(n), which is higher than
  99  * O(log(n)) provided by the rest of this API.
 100  */
 101 extern void *heap_cherrypick(struct ptr_heap *heap, void *p);
 102
 103 /**
 104  * heap_replace_max - replace the the largest element from the heap
 105  * @heap: the heap to be operated on
 106  * @p: the pointer to be inserted as topmost element replacement
 107  *
 108  * Returns the largest element in the heap. It removes this element from the
 109  * heap. The heap is rebalanced only once after the insertion. Returns NULL if
 110  * the heap is empty.
 111  *
 112  * This is the equivalent of calling heap_remove() and then heap_insert(), but
 113  * it only rebalances the heap once. It never allocates memory.
 114  */
 115 extern void *heap_replace_max(struct ptr_heap *heap, void *p);
 116
 117 #endif /* _LTTNG_PRIO_HEAP_H */