third_party/libevent/min_heap.h

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