1/*
2 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
3 *
4 * Copyright (c) 2006 Maxim Yegorushkin <maxim.yegorushkin@gmail.com>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 *    derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28#ifndef _MIN_HEAP_H_
29#define _MIN_HEAP_H_
30
31#include "event2/event-config.h"
32#include "event2/event.h"
33#include "event2/event_struct.h"
34#include "event2/util.h"
35#include "util-internal.h"
36#include "mm-internal.h"
37
38typedef struct min_heap
39{
40	struct event** p;
41	unsigned n, a;
42} min_heap_t;
43
44static inline void	     min_heap_ctor(min_heap_t* s);
45static inline void	     min_heap_dtor(min_heap_t* s);
46static inline void	     min_heap_elem_init(struct event* e);
47static inline int	     min_heap_elt_is_top(const struct event *e);
48static inline int	     min_heap_elem_greater(struct event *a, struct event *b);
49static inline int	     min_heap_empty(min_heap_t* s);
50static inline unsigned	     min_heap_size(min_heap_t* s);
51static inline struct event*  min_heap_top(min_heap_t* s);
52static inline int	     min_heap_reserve(min_heap_t* s, unsigned n);
53static inline int	     min_heap_push(min_heap_t* s, struct event* e);
54static inline struct event*  min_heap_pop(min_heap_t* s);
55static inline int	     min_heap_erase(min_heap_t* s, struct event* e);
56static inline void	     min_heap_shift_up_(min_heap_t* s, unsigned hole_index, struct event* e);
57static inline void	     min_heap_shift_down_(min_heap_t* s, unsigned hole_index, struct event* e);
58
59int min_heap_elem_greater(struct event *a, struct event *b)
60{
61	return evutil_timercmp(&a->ev_timeout, &b->ev_timeout, >);
62}
63
64void min_heap_ctor(min_heap_t* s) { s->p = 0; s->n = 0; s->a = 0; }
65void min_heap_dtor(min_heap_t* s) { if (s->p) mm_free(s->p); }
66void min_heap_elem_init(struct event* e) { e->ev_timeout_pos.min_heap_idx = -1; }
67int min_heap_empty(min_heap_t* s) { return 0u == s->n; }
68unsigned min_heap_size(min_heap_t* s) { return s->n; }
69struct event* min_heap_top(min_heap_t* s) { return s->n ? *s->p : 0; }
70
71int min_heap_push(min_heap_t* s, struct event* e)
72{
73	if (min_heap_reserve(s, s->n + 1))
74		return -1;
75	min_heap_shift_up_(s, s->n++, e);
76	return 0;
77}
78
79struct event* min_heap_pop(min_heap_t* s)
80{
81	if (s->n)
82	{
83		struct event* e = *s->p;
84		min_heap_shift_down_(s, 0u, s->p[--s->n]);
85		e->ev_timeout_pos.min_heap_idx = -1;
86		return e;
87	}
88	return 0;
89}
90
91int min_heap_elt_is_top(const struct event *e)
92{
93	return e->ev_timeout_pos.min_heap_idx == 0;
94}
95
96int min_heap_erase(min_heap_t* s, struct event* e)
97{
98	if (-1 != e->ev_timeout_pos.min_heap_idx)
99	{
100		struct event *last = s->p[--s->n];
101		unsigned parent = (e->ev_timeout_pos.min_heap_idx - 1) / 2;
102		/* we replace e with the last element in the heap.  We might need to
103		   shift it upward if it is less than its parent, or downward if it is
104		   greater than one or both its children. Since the children are known
105		   to be less than the parent, it can't need to shift both up and
106		   down. */
107		if (e->ev_timeout_pos.min_heap_idx > 0 && min_heap_elem_greater(s->p[parent], last))
108			min_heap_shift_up_(s, e->ev_timeout_pos.min_heap_idx, last);
109		else
110			min_heap_shift_down_(s, e->ev_timeout_pos.min_heap_idx, last);
111		e->ev_timeout_pos.min_heap_idx = -1;
112		return 0;
113	}
114	return -1;
115}
116
117int min_heap_reserve(min_heap_t* s, unsigned n)
118{
119	if (s->a < n)
120	{
121		struct event** p;
122		unsigned a = s->a ? s->a * 2 : 8;
123		if (a < n)
124			a = n;
125		if (!(p = (struct event**)mm_realloc(s->p, a * sizeof *p)))
126			return -1;
127		s->p = p;
128		s->a = a;
129	}
130	return 0;
131}
132
133void min_heap_shift_up_(min_heap_t* s, unsigned hole_index, struct event* e)
134{
135    unsigned parent = (hole_index - 1) / 2;
136    while (hole_index && min_heap_elem_greater(s->p[parent], e))
137    {
138	(s->p[hole_index] = s->p[parent])->ev_timeout_pos.min_heap_idx = hole_index;
139	hole_index = parent;
140	parent = (hole_index - 1) / 2;
141    }
142    (s->p[hole_index] = e)->ev_timeout_pos.min_heap_idx = hole_index;
143}
144
145void min_heap_shift_down_(min_heap_t* s, unsigned hole_index, struct event* e)
146{
147    unsigned min_child = 2 * (hole_index + 1);
148    while (min_child <= s->n)
149	{
150	min_child -= min_child == s->n || min_heap_elem_greater(s->p[min_child], s->p[min_child - 1]);
151	if (!(min_heap_elem_greater(e, s->p[min_child])))
152	    break;
153	(s->p[hole_index] = s->p[min_child])->ev_timeout_pos.min_heap_idx = hole_index;
154	hole_index = min_child;
155	min_child = 2 * (hole_index + 1);
156	}
157    (s->p[hole_index] = e)->ev_timeout_pos.min_heap_idx = hole_index;
158}
159
160#endif /* _MIN_HEAP_H_ */
161