Merge branch 'rs/nth-switch-code-simplification'
[git/git.git] / prio-queue.c
1 #include "cache.h"
2 #include "prio-queue.h"
3
4 static inline int compare(struct prio_queue *queue, int i, int j)
5 {
6 int cmp = queue->compare(queue->array[i].data, queue->array[j].data,
7 queue->cb_data);
8 if (!cmp)
9 cmp = queue->array[i].ctr - queue->array[j].ctr;
10 return cmp;
11 }
12
13 static inline void swap(struct prio_queue *queue, int i, int j)
14 {
15 SWAP(queue->array[i], queue->array[j]);
16 }
17
18 void prio_queue_reverse(struct prio_queue *queue)
19 {
20 int i, j;
21
22 if (queue->compare != NULL)
23 BUG("prio_queue_reverse() on non-LIFO queue");
24 for (i = 0; i < (j = (queue->nr - 1) - i); i++)
25 swap(queue, i, j);
26 }
27
28 void clear_prio_queue(struct prio_queue *queue)
29 {
30 FREE_AND_NULL(queue->array);
31 queue->nr = 0;
32 queue->alloc = 0;
33 queue->insertion_ctr = 0;
34 }
35
36 void prio_queue_put(struct prio_queue *queue, void *thing)
37 {
38 int ix, parent;
39
40 /* Append at the end */
41 ALLOC_GROW(queue->array, queue->nr + 1, queue->alloc);
42 queue->array[queue->nr].ctr = queue->insertion_ctr++;
43 queue->array[queue->nr].data = thing;
44 queue->nr++;
45 if (!queue->compare)
46 return; /* LIFO */
47
48 /* Bubble up the new one */
49 for (ix = queue->nr - 1; ix; ix = parent) {
50 parent = (ix - 1) / 2;
51 if (compare(queue, parent, ix) <= 0)
52 break;
53
54 swap(queue, parent, ix);
55 }
56 }
57
58 void *prio_queue_get(struct prio_queue *queue)
59 {
60 void *result;
61 int ix, child;
62
63 if (!queue->nr)
64 return NULL;
65 if (!queue->compare)
66 return queue->array[--queue->nr].data; /* LIFO */
67
68 result = queue->array[0].data;
69 if (!--queue->nr)
70 return result;
71
72 queue->array[0] = queue->array[queue->nr];
73
74 /* Push down the one at the root */
75 for (ix = 0; ix * 2 + 1 < queue->nr; ix = child) {
76 child = ix * 2 + 1; /* left */
77 if (child + 1 < queue->nr &&
78 compare(queue, child, child + 1) >= 0)
79 child++; /* use right child */
80
81 if (compare(queue, ix, child) <= 0)
82 break;
83
84 swap(queue, child, ix);
85 }
86 return result;
87 }
88
89 void *prio_queue_peek(struct prio_queue *queue)
90 {
91 if (!queue->nr)
92 return NULL;
93 if (!queue->compare)
94 return queue->array[queue->nr - 1].data;
95 return queue->array[0].data;
96 }