forked from beanstalkd/beanstalkd
-
Notifications
You must be signed in to change notification settings - Fork 0
/
pq.c
142 lines (110 loc) · 2.54 KB
/
pq.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
/* pq.c - priority queue */
/* Copyright (C) 2007 Keith Rarick and Philotic Inc.
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <stdio.h>
#include "pq.h"
pq
make_pq(unsigned int size, job_cmp_fn cmp)
{
pq q;
q = malloc(sizeof(struct pq) + size * sizeof(job));
if (!q) return NULL;
q->size = size;
q->used = 0;
q->cmp = cmp;
return q;
}
static void
swap(pq q, unsigned int a, unsigned int b)
{
job j;
j = q->heap[a];
q->heap[a] = q->heap[b];
q->heap[b] = j;
}
#define PARENT(i) (((i-1))>>1)
#define CHILD_LEFT(i) (((i)<<1)+1)
#define CHILD_RIGHT(i) (((i)<<1)+2)
static int
cmp(pq q, unsigned int a, unsigned int b)
{
return q->cmp(q->heap[a], q->heap[b]);
}
static void
bubble_up(pq q, unsigned int k)
{
int p;
if (k == 0) return;
p = PARENT(k);
if (cmp(q, p, k) <= 0) return;
swap(q, k, p);
bubble_up(q, p);
}
static void
bubble_down(pq q, unsigned int k)
{
int l, r, s;
l = CHILD_LEFT(k);
r = CHILD_RIGHT(k);
s = k;
if (l < q->used && cmp(q, l, k) < 0) s = l;
if (r < q->used && cmp(q, r, s) < 0) s = r;
if (s == k) return; /* already satisfies the heap property */
swap(q, k, s);
bubble_down(q, s);
}
/* assumes there is at least one item in the queue */
static void
delete_min(pq q)
{
q->heap[0] = q->heap[--q->used];
if (q->used) bubble_down(q, 0);
}
int
pq_give(pq q, job j)
{
int k;
if (q->used >= q->size) return 0;
k = q->used++;
q->heap[k] = j;
bubble_up(q, k);
return 1;
}
job
pq_take(pq q)
{
job j;
if (q->used == 0) return NULL;
j = q->heap[0];
delete_min(q);
return j;
}
job
pq_peek(pq q)
{
if (q->used == 0) return NULL;
return q->heap[0];
}
job
pq_find(pq q, unsigned long long int id)
{
unsigned int i;
for (i = 0; i < q->used; i++) if (q->heap[i]->id == id) return q->heap[i];
return NULL;
}
unsigned int
pq_used(pq q)
{
return q->used;
}