include/babeltrace/prio_heap.h

   1 #ifndef _BABELTRACE_PRIO_HEAP_H
   2 #define _BABELTRACE_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  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  23  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  25  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  26  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  27  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  28  * SOFTWARE.
  29  */
  30
  31 #include <unistd.h>
  32 #include <babeltrace/babeltrace-internal.h>
  33
  34 struct ptr_heap {
  35         size_t len, alloc_len;
  36         void **ptrs;
  37         int (*gt)(void *a, void *b);
  38 };
  39
  40 #ifdef DEBUG_HEAP
  41 void check_heap(const struct ptr_heap *heap);
  42 #else
  43 static inline
  44 void check_heap(const struct ptr_heap *heap)
  45 {
  46 }
  47 #endif
  48
  49 /**
  50  * heap_maximum - return the largest element in the heap
  51  * @heap: the heap to be operated on
  52  *
  53  * Returns the largest element in the heap, without performing any modification
  54  * to the heap structure. Returns NULL if the heap is empty.
  55  */
  56 static inline void *heap_maximum(const struct ptr_heap *heap)
  57 {
  58         check_heap(heap);
  59         return likely(heap->len) ? heap->ptrs[0] : NULL;
  60 }
  61
  62 /**
  63  * heap_init - initialize the heap
  64  * @heap: the heap to initialize
  65  * @alloc_len: number of elements initially allocated
  66  * @gt: function to compare the elements
  67  *
  68  * Returns -ENOMEM if out of memory.
  69  */
  70 extern int heap_init(struct ptr_heap *heap,
  71                      size_t alloc_len,
  72                      int gt(void *a, void *b));
  73
  74 /**
  75  * heap_free - free the heap
  76  * @heap: the heap to free
  77  */
  78 extern void heap_free(struct ptr_heap *heap);
  79
  80 /**
  81  * 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 heap_insert(struct ptr_heap *heap, void *p);
  90
  91 /**
  92  * 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 *heap_remove(struct ptr_heap *heap);
  99
 100 /**
 101  * 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 *heap_cherrypick(struct ptr_heap *heap, void *p);
 110
 111 /**
 112  * 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 *heap_replace_max(struct ptr_heap *heap, void *p);
 124
 125 /**
 126  * heap_copy - copy a heap
 127  * @dst: the destination heap (must be allocated)
 128  * @src: the source heap
 129  *
 130  * Returns -ENOMEM if out of memory.
 131  */
 132 extern int heap_copy(struct ptr_heap *dst, struct ptr_heap *src);
 133
 134 #endif /* _BABELTRACE_PRIO_HEAP_H */