release/src/router/dnscrypt/src/libevent/minheap-internal.h

   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
  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
  64 void min_heap_ctor(min_heap_t* s) { s->p = 0; s->n = 0; s->a = 0; }
  65 void min_heap_dtor(min_heap_t* s) { if (s->p) mm_free(s->p); }
  66 void min_heap_elem_init(struct event* e) { e->ev_timeout_pos.min_heap_idx = -1; }
  67 int min_heap_empty(min_heap_t* s) { return 0u == s->n; }
  68 unsigned min_heap_size(min_heap_t* s) { return s->n; }
  69 struct event* min_heap_top(min_heap_t* s) { return s->n ? *s->p : 0; }
  70
  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
  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
  91 int min_heap_elt_is_top(const struct event *e)
  92 {
  93         return e->ev_timeout_pos.min_heap_idx == 0;
  94 }
  95
  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
 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
 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
 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_ */