183 lines
5.2 KiB
C
183 lines
5.2 KiB
C
/* $OpenBSD: min_heap.h,v 1.6 2019/04/29 17:11:52 tobias Exp $ */
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/*
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* Copyright (c) 2006 Maxim Yegorushkin <maxim.yegorushkin@gmail.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _MIN_HEAP_H_
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#define _MIN_HEAP_H_
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#include "event.h"
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typedef struct min_heap {
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struct event **p;
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size_t n, a;
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} min_heap_t;
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static inline void min_heap_ctor(min_heap_t * s);
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static inline void min_heap_dtor(min_heap_t * s);
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static inline void min_heap_elem_init(struct event * e);
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static inline int min_heap_elem_greater(struct event * a, struct event * b);
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static inline int min_heap_empty(min_heap_t * s);
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static inline size_t min_heap_size(min_heap_t * s);
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static inline struct event *min_heap_top(min_heap_t * s);
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static inline int min_heap_reserve(min_heap_t * s, size_t n);
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static inline int min_heap_push(min_heap_t * s, struct event * e);
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static inline struct event *min_heap_pop(min_heap_t * s);
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static inline int min_heap_erase(min_heap_t * s, struct event * e);
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static inline void min_heap_shift_up_(min_heap_t * s, size_t hole_index, struct event * e);
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static inline void min_heap_shift_down_(min_heap_t * s, size_t hole_index, struct event * e);
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int
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min_heap_elem_greater(struct event * a, struct event * b)
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{
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return timercmp(&a->ev_timeout, &b->ev_timeout, >);
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}
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void
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min_heap_ctor(min_heap_t * s)
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{
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s->p = 0;
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s->n = 0;
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s->a = 0;
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}
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void min_heap_dtor(min_heap_t * s) {
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if (s->p)
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free(s->p);
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}
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void
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min_heap_elem_init(struct event * e)
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{
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e->min_heap_idx = SIZE_MAX;
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}
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int
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min_heap_empty(min_heap_t * s)
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{
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return 0 == s->n;
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}
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size_t
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min_heap_size(min_heap_t * s)
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{
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return s->n;
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}
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struct event *
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min_heap_top(min_heap_t * s)
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{
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return s->n ? *s->p : 0;
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}
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int
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min_heap_push(min_heap_t * s, struct event * e)
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{
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if (min_heap_reserve(s, s->n + 1))
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return -1;
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min_heap_shift_up_(s, s->n++, e);
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return 0;
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}
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struct event *
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min_heap_pop(min_heap_t * s)
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{
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if (s->n) {
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struct event *e = *s->p;
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min_heap_shift_down_(s, 0, s->p[--s->n]);
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e->min_heap_idx = SIZE_MAX;
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return e;
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}
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return 0;
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}
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int
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min_heap_erase(min_heap_t * s, struct event * e)
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{
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if (e->min_heap_idx != SIZE_MAX) {
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struct event *last = s->p[--s->n];
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size_t parent = (e->min_heap_idx - 1) / 2;
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/*
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* we replace e with the last element in the heap. We might
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* need to shift it upward if it is less than its parent, or
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* downward if it is greater than one or both its children.
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* Since the children are known to be less than the parent,
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* it can't need to shift both up and down.
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*/
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if (e->min_heap_idx > 0 && min_heap_elem_greater(s->p[parent], last))
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min_heap_shift_up_(s, e->min_heap_idx, last);
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else
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min_heap_shift_down_(s, e->min_heap_idx, last);
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e->min_heap_idx = SIZE_MAX;
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return 0;
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}
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return -1;
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}
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int
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min_heap_reserve(min_heap_t * s, size_t n)
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{
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if (s->a < n) {
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struct event **p;
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size_t a = s->a ? s->a * 2 : 8;
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if (a < n)
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a = n;
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if (!(p = recallocarray(s->p, s->a, a, sizeof *p)))
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return -1;
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s->p = p;
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s->a = a;
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}
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return 0;
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}
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void
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min_heap_shift_up_(min_heap_t * s, size_t hole_index, struct event * e)
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{
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size_t parent = (hole_index - 1) / 2;
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while (hole_index && min_heap_elem_greater(s->p[parent], e)) {
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s->p[hole_index] = s->p[parent];
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s->p[hole_index]->min_heap_idx = hole_index;
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hole_index = parent;
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parent = (hole_index - 1) / 2;
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}
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e->min_heap_idx = hole_index;
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s->p[hole_index] = e;
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}
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void
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min_heap_shift_down_(min_heap_t * s, size_t hole_index, struct event * e)
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{
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size_t min_child = 2 * (hole_index + 1);
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while (min_child <= s->n) {
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if (min_child == s->n ||
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min_heap_elem_greater(s->p[min_child], s->p[min_child - 1]))
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min_child -= 1;
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if (!(min_heap_elem_greater(e, s->p[min_child])))
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break;
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s->p[hole_index] = s->p[min_child];
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s->p[hole_index]->min_heap_idx = hole_index;
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hole_index = min_child;
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min_child = 2 * (hole_index + 1);
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}
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min_heap_shift_up_(s, hole_index, e);
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}
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#endif /* _MIN_HEAP_H_ */
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