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 }