[babeltrace.git] / src / lib / prio-heap / prio-heap.h

/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * Static-sized priority heap containing pointers. Based on CLRS,
 * chapter 6.
 */

#ifndef _BABELTRACE_PRIO_HEAP_H
#define _BABELTRACE_PRIO_HEAP_H

#include <unistd.h>
#include "common/macros.h"

struct ptr_heap {
	size_t len, alloc_len;
	void **ptrs;
	int (*gt)(void *a, void *b);
};

#ifdef DEBUG_HEAP
void check_heap(const struct ptr_heap *heap);
#else
static inline
void check_heap(const struct ptr_heap *heap)
{
}
#endif

/**
 * bt_heap_maximum - return the largest element in the heap
 * @heap: the heap to be operated on
 *
 * Returns the largest element in the heap, without performing any modification
 * to the heap structure. Returns NULL if the heap is empty.
 */
static inline void *bt_heap_maximum(const struct ptr_heap *heap)
{
	check_heap(heap);
	return G_LIKELY(heap->len) ? heap->ptrs[0] : NULL;
}

/**
 * bt_heap_init - initialize the heap
 * @heap: the heap to initialize
 * @alloc_len: number of elements initially allocated
 * @gt: function to compare the elements
 *
 * Returns -ENOMEM if out of memory.
 */
BT_HIDDEN
extern int bt_heap_init(struct ptr_heap *heap,
		     size_t alloc_len,
		     int gt(void *a, void *b));

/**
 * bt_heap_free - free the heap
 * @heap: the heap to free
 */
BT_HIDDEN
extern void bt_heap_free(struct ptr_heap *heap);

/**
 * bt_heap_insert - insert an element into the heap
 * @heap: the heap to be operated on
 * @p: the element to add
 *
 * Insert an element into the heap.
 *
 * Returns -ENOMEM if out of memory.
 */
BT_HIDDEN
extern int bt_heap_insert(struct ptr_heap *heap, void *p);

/**
 * bt_heap_remove - remove the largest element from the heap
 * @heap: the heap to be operated on
 *
 * Returns the largest element in the heap. It removes this element from the
 * heap. Returns NULL if the heap is empty.
 */
BT_HIDDEN
extern void *bt_heap_remove(struct ptr_heap *heap);

/**
 * bt_heap_cherrypick - remove a given element from the heap
 * @heap: the heap to be operated on
 * @p: the element
 *
 * Remove the given element from the heap. Return the element if present, else
 * return NULL. This algorithm has a complexity of O(n), which is higher than
 * O(log(n)) provided by the rest of this API.
 */
BT_HIDDEN
extern void *bt_heap_cherrypick(struct ptr_heap *heap, void *p);

/**
 * bt_heap_replace_max - replace the the largest element from the heap
 * @heap: the heap to be operated on
 * @p: the pointer to be inserted as topmost element replacement
 *
 * Returns the largest element in the heap. It removes this element from the
 * heap. The heap is rebalanced only once after the insertion. Returns NULL if
 * the heap is empty.
 *
 * This is the equivalent of calling bt_heap_remove() and then bt_heap_insert(), but
 * it only rebalances the heap once. It never allocates memory.
 */
BT_HIDDEN
extern void *bt_heap_replace_max(struct ptr_heap *heap, void *p);

/**
 * bt_heap_copy - copy a heap
 * @dst: the destination heap (must be allocated)
 * @src: the source heap
 *
 * Returns -ENOMEM if out of memory.
 */
BT_HIDDEN
extern int bt_heap_copy(struct ptr_heap *dst, struct ptr_heap *src);

#endif /* _BABELTRACE_PRIO_HEAP_H */
Commit	Line	Data
	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	BT_HIDDEN
	53	extern int bt_heap_init(struct ptr_heap *heap,
	54	size_t alloc_len,
	55	int gt(void a, void b));
	56
	57	/**
	58	* bt_heap_free - free the heap
	59	* @heap: the heap to free
	60	*/
	61	BT_HIDDEN
	62	extern void bt_heap_free(struct ptr_heap *heap);
	63
	64	/**
	65	* bt_heap_insert - insert an element into the heap
	66	* @heap: the heap to be operated on
	67	* @p: the element to add
	68	*
	69	* Insert an element into the heap.
	70	*
	71	* Returns -ENOMEM if out of memory.
	72	*/
	73	BT_HIDDEN
	74	extern int bt_heap_insert(struct ptr_heap heap, void p);
	75
	76	/**
	77	* bt_heap_remove - remove the largest element from the heap
	78	* @heap: the heap to be operated on
	79	*
	80	* Returns the largest element in the heap. It removes this element from the
	81	* heap. Returns NULL if the heap is empty.
	82	*/
	83	BT_HIDDEN
	84	extern void bt_heap_remove(struct ptr_heap heap);
	85
	86	/**
	87	* bt_heap_cherrypick - remove a given element from the heap
	88	* @heap: the heap to be operated on
	89	* @p: the element
	90	*
	91	* Remove the given element from the heap. Return the element if present, else
	92	* return NULL. This algorithm has a complexity of O(n), which is higher than
	93	* O(log(n)) provided by the rest of this API.
	94	*/
	95	BT_HIDDEN
	96	extern void bt_heap_cherrypick(struct ptr_heap heap, void *p);
	97
	98	/**
	99	* bt_heap_replace_max - replace the the largest element from the heap
	100	* @heap: the heap to be operated on
	101	* @p: the pointer to be inserted as topmost element replacement
	102	*
	103	* Returns the largest element in the heap. It removes this element from the
	104	* heap. The heap is rebalanced only once after the insertion. Returns NULL if
	105	* the heap is empty.
	106	*
	107	* This is the equivalent of calling bt_heap_remove() and then bt_heap_insert(), but
	108	* it only rebalances the heap once. It never allocates memory.
	109	*/
	110	BT_HIDDEN
	111	extern void bt_heap_replace_max(struct ptr_heap heap, void *p);
	112
	113	/**
	114	* bt_heap_copy - copy a heap
	115	* @dst: the destination heap (must be allocated)
	116	* @src: the source heap
	117	*
	118	* Returns -ENOMEM if out of memory.
	119	*/
	120	BT_HIDDEN
	121	extern int bt_heap_copy(struct ptr_heap dst, struct ptr_heap src);
	122
	123	#endif /* _BABELTRACE_PRIO_HEAP_H */