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
|
/*
* Copyright (C) the libgit2 contributors. All rights reserved.
*
* This file is part of libgit2, distributed under the GNU GPL v2 with
* a Linking Exception. For full terms see the included COPYING file.
*/
#include "pqueue.h"
#include "util.h"
#define PQUEUE_LCHILD_OF(I) (((I)<<1)+1)
#define PQUEUE_RCHILD_OF(I) (((I)<<1)+2)
#define PQUEUE_PARENT_OF(I) (((I)-1)>>1)
int git_pqueue_init(
git_pqueue *pq,
uint32_t flags,
size_t init_size,
git_vector_cmp cmp)
{
int error = git_vector_init(pq, init_size, cmp);
if (!error) {
/* mix in our flags */
pq->flags |= flags;
/* if fixed size heap, pretend vector is exactly init_size elements */
if ((flags & GIT_PQUEUE_FIXED_SIZE) && init_size > 0)
pq->_alloc_size = init_size;
}
return error;
}
static void pqueue_up(git_pqueue *pq, size_t el)
{
size_t parent_el = PQUEUE_PARENT_OF(el);
void *kid = git_vector_get(pq, el);
while (el > 0) {
void *parent = pq->contents[parent_el];
if (pq->_cmp(parent, kid) <= 0)
break;
pq->contents[el] = parent;
el = parent_el;
parent_el = PQUEUE_PARENT_OF(el);
}
pq->contents[el] = kid;
}
static void pqueue_down(git_pqueue *pq, size_t el)
{
void *parent = git_vector_get(pq, el), *kid, *rkid;
while (1) {
size_t kid_el = PQUEUE_LCHILD_OF(el);
if ((kid = git_vector_get(pq, kid_el)) == NULL)
break;
if ((rkid = git_vector_get(pq, kid_el + 1)) != NULL &&
pq->_cmp(kid, rkid) > 0) {
kid = rkid;
kid_el += 1;
}
if (pq->_cmp(parent, kid) <= 0)
break;
pq->contents[el] = kid;
el = kid_el;
}
pq->contents[el] = parent;
}
int git_pqueue_insert(git_pqueue *pq, void *item)
{
int error = 0;
/* if heap is full, pop the top element if new one should replace it */
if ((pq->flags & GIT_PQUEUE_FIXED_SIZE) != 0 &&
pq->length >= pq->_alloc_size)
{
/* skip this item if below min item in heap or if
* we do not have a comparison function */
if (!pq->_cmp || pq->_cmp(item, git_vector_get(pq, 0)) <= 0)
return 0;
/* otherwise remove the min item before inserting new */
(void)git_pqueue_pop(pq);
}
if (!(error = git_vector_insert(pq, item)) && pq->_cmp)
pqueue_up(pq, pq->length - 1);
return error;
}
void *git_pqueue_pop(git_pqueue *pq)
{
void *rval;
if (!pq->_cmp) {
rval = git_vector_last(pq);
} else {
rval = git_pqueue_get(pq, 0);
}
if (git_pqueue_size(pq) > 1 && pq->_cmp) {
/* move last item to top of heap, shrink, and push item down */
pq->contents[0] = git_vector_last(pq);
git_vector_pop(pq);
pqueue_down(pq, 0);
} else {
/* all we need to do is shrink the heap in this case */
git_vector_pop(pq);
}
return rval;
}
|
