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
38 typedef struct min_heap
39 {
40 struct event** p;
41 unsigned n, a;
42 } min_heap_t;
43
44 static inline void min_heap_ctor(min_heap_t* s);
45 static inline void min_heap_dtor(min_heap_t* s);
46 static inline void min_heap_elem_init(struct event* e);
47 static inline int min_heap_elt_is_top(const struct event *e);
48 static inline int min_heap_elem_greater(struct event *a, struct event *b);
49 static inline int min_heap_empty(min_heap_t* s);
50 static inline unsigned min_heap_size(min_heap_t* s);
51 static inline struct event* min_heap_top(min_heap_t* s);
52 static inline int min_heap_reserve(min_heap_t* s, unsigned n);
53 static inline int min_heap_push(min_heap_t* s, struct event* e);
54 static inline struct event* min_heap_pop(min_heap_t* s);
55 static inline int min_heap_erase(min_heap_t* s, struct event* e);
56 static inline void min_heap_shift_up_(min_heap_t* s, unsigned hole_index, struct event* e);
57 static inline void min_heap_shift_down_(min_heap_t* s, unsigned hole_index, struct event* e);
58
min_heap_elem_greater(struct event * a,struct event * b)59 int min_heap_elem_greater(struct event *a, struct event *b)
60 {
61 return evutil_timercmp(&a->ev_timeout, &b->ev_timeout, >);
62 }
63
min_heap_ctor(min_heap_t * s)64 void min_heap_ctor(min_heap_t* s) { s->p = 0; s->n = 0; s->a = 0; }
min_heap_dtor(min_heap_t * s)65 void min_heap_dtor(min_heap_t* s) { if (s->p) mm_free(s->p); }
min_heap_elem_init(struct event * e)66 void min_heap_elem_init(struct event* e) { e->ev_timeout_pos.min_heap_idx = -1; }
min_heap_empty(min_heap_t * s)67 int min_heap_empty(min_heap_t* s) { return 0u == s->n; }
min_heap_size(min_heap_t * s)68 unsigned min_heap_size(min_heap_t* s) { return s->n; }
min_heap_top(min_heap_t * s)69 struct event* min_heap_top(min_heap_t* s) { return s->n ? *s->p : 0; }
70
min_heap_push(min_heap_t * s,struct event * e)71 int 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
min_heap_pop(min_heap_t * s)79 struct 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
min_heap_elt_is_top(const struct event * e)91 int min_heap_elt_is_top(const struct event *e)
92 {
93 return e->ev_timeout_pos.min_heap_idx == 0;
94 }
95
min_heap_erase(min_heap_t * s,struct event * e)96 int 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
min_heap_reserve(min_heap_t * s,unsigned n)117 int 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
min_heap_shift_up_(min_heap_t * s,unsigned hole_index,struct event * e)133 void 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
min_heap_shift_down_(min_heap_t * s,unsigned hole_index,struct event * e)145 void 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