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