freshlybakedca.ke
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1#ifndef PRIO_QUEUE_H
2#define PRIO_QUEUE_H
3
4/*
5 * A priority queue implementation, primarily for keeping track of
6 * commits in the 'date-order' so that we process them from new to old
7 * as they are discovered, but can be used to hold any pointer to
8 * struct. The caller is responsible for supplying a function to
9 * compare two "things".
10 *
11 * Alternatively, this data structure can also be used as a LIFO stack
12 * by specifying NULL as the comparison function.
13 */
14
15/*
16 * Compare two "things", one and two; the third parameter is cb_data
17 * in the prio_queue structure. The result is returned as a sign of
18 * the return value, being the same as the sign of the result of
19 * subtracting "two" from "one" (i.e. negative if "one" sorts earlier
20 * than "two").
21 */
22typedef int (*prio_queue_compare_fn)(const void *one, const void *two, void *cb_data);
23
24struct prio_queue_entry {
25 size_t ctr;
26 void *data;
27};
28
29struct prio_queue {
30 prio_queue_compare_fn compare;
31 size_t insertion_ctr;
32 void *cb_data;
33 size_t alloc, nr;
34 struct prio_queue_entry *array;
35};
36
37/*
38 * Add the "thing" to the queue.
39 */
40void prio_queue_put(struct prio_queue *, void *thing);
41
42/*
43 * Extract the "thing" that compares the smallest out of the queue,
44 * or NULL. If compare function is NULL, the queue acts as a LIFO
45 * stack.
46 */
47void *prio_queue_get(struct prio_queue *);
48
49/*
50 * Gain access to the "thing" that would be returned by
51 * prio_queue_get, but do not remove it from the queue.
52 */
53void *prio_queue_peek(struct prio_queue *);
54
55/*
56 * Replace the "thing" that compares the smallest with a new "thing",
57 * like prio_queue_get()+prio_queue_put() would do, but in a more
58 * efficient way. Does the same as prio_queue_put() if the queue is
59 * empty.
60 */
61void prio_queue_replace(struct prio_queue *queue, void *thing);
62
63void clear_prio_queue(struct prio_queue *);
64
65/* Reverse the LIFO elements */
66void prio_queue_reverse(struct prio_queue *);
67
68#endif /* PRIO_QUEUE_H */