Annotation of embedaddon/libevent/min_heap.h, revision 1.1
1.1 ! misho 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) { if(s->p) 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_ */
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