src/lib/prio-heap/prio-heap.h

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Static-sized priority heap containing pointers. Based on CLRS,
   7  * chapter 6.
   8  */
   9
  10 #ifndef _BABELTRACE_PRIO_HEAP_H
  11 #define _BABELTRACE_PRIO_HEAP_H
  12
  13 #include <unistd.h>
  14 #include "common/macros.h"
  15
  16 struct ptr_heap {
  17         size_t len, alloc_len;
  18         void **ptrs;
  19         int (*gt)(void *a, void *b);
  20 };
  21
  22 #ifdef DEBUG_HEAP
  23 void check_heap(const struct ptr_heap *heap);
  24 #else
  25 static inline
  26 void check_heap(const struct ptr_heap *heap)
  27 {
  28 }
  29 #endif
  30
  31 /**
  32  * bt_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 *bt_heap_maximum(const struct ptr_heap *heap)
  39 {
  40         check_heap(heap);
  41         return G_LIKELY(heap->len) ? heap->ptrs[0] : NULL;
  42 }
  43
  44 /**
  45  * bt_heap_init - initialize the heap
  46  * @heap: the heap to initialize
  47  * @alloc_len: number of elements initially allocated
  48  * @gt: function to compare the elements
  49  *
  50  * Returns -ENOMEM if out of memory.
  51  */
  52 extern int bt_heap_init(struct ptr_heap *heap,
  53                      size_t alloc_len,
  54                      int gt(void *a, void *b));
  55
  56 /**
  57  * bt_heap_free - free the heap
  58  * @heap: the heap to free
  59  */
  60 extern void bt_heap_free(struct ptr_heap *heap);
  61
  62 /**
  63  * bt_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 bt_heap_insert(struct ptr_heap *heap, void *p);
  72
  73 /**
  74  * bt_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 *bt_heap_remove(struct ptr_heap *heap);
  81
  82 /**
  83  * bt_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 *bt_heap_cherrypick(struct ptr_heap *heap, void *p);
  92
  93 /**
  94  * bt_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 bt_heap_remove() and then bt_heap_insert(), but
 103  * it only rebalances the heap once. It never allocates memory.
 104  */
 105 extern void *bt_heap_replace_max(struct ptr_heap *heap, void *p);
 106
 107 /**
 108  * bt_heap_copy - copy a heap
 109  * @dst: the destination heap (must be allocated)
 110  * @src: the source heap
 111  *
 112  * Returns -ENOMEM if out of memory.
 113  */
 114 extern int bt_heap_copy(struct ptr_heap *dst, struct ptr_heap *src);
 115
 116 #endif /* _BABELTRACE_PRIO_HEAP_H */