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#ifndef PRIO_QUEUE_H
#define PRIO_QUEUE_H
/*
* A priority queue implementation, primarily for keeping track of
* commits in the 'date-order' so that we process them from new to old
* as they are discovered, but can be used to hold any pointer to
* struct. The caller is responsible for supplying a function to
* compare two "things".
*
* Alternatively, this data structure can also be used as a LIFO stack
* by specifying NULL as the comparison function.
*/
/*
* Compare two "things", one and two; the third parameter is cb_data
* in the prio_queue structure. The result is returned as a sign of
* the return value, being the same as the sign of the result of
* subtracting "two" from "one" (i.e. negative if "one" sorts earlier
* than "two").
*/
typedef int (*prio_queue_compare_fn)(const void *one, const void *two, void *cb_data);
struct prio_queue_entry {
unsigned ctr;
void *data;
};
struct prio_queue {
prio_queue_compare_fn compare;
unsigned insertion_ctr;
void *cb_data;
int alloc, nr;
struct prio_queue_entry *array;
};
/*
* Add the "thing" to the queue.
*/
extern void prio_queue_put(struct prio_queue *, void *thing);
/*
* Extract the "thing" that compares the smallest out of the queue,
* or NULL. If compare function is NULL, the queue acts as a LIFO
* stack.
*/
extern void *prio_queue_get(struct prio_queue *);
/*
* Gain access to the "thing" that would be returned by
* prio_queue_get, but do not remove it from the queue.
*/
extern void *prio_queue_peek(struct prio_queue *);
extern void clear_prio_queue(struct prio_queue *);
/* Reverse the LIFO elements */
extern void prio_queue_reverse(struct prio_queue *);
#endif /* PRIO_QUEUE_H */
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