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                 die("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(queue->array);
  31         queue->nr = 0;
  32         queue->alloc = 0;
  33         queue->array = NULL;
  34         queue->insertion_ctr = 0;
  35 }
  36
  37 void prio_queue_put(struct prio_queue *queue, void *thing)
  38 {
  39         int ix, parent;
  40
  41         /* Append at the end */
  42         ALLOC_GROW(queue->array, queue->nr + 1, queue->alloc);
  43         queue->array[queue->nr].ctr = queue->insertion_ctr++;
  44         queue->array[queue->nr].data = thing;
  45         queue->nr++;
  46         if (!queue->compare)
  47                 return; /* LIFO */
  48
  49         /* Bubble up the new one */
  50         for (ix = queue->nr - 1; ix; ix = parent) {
  51                 parent = (ix - 1) / 2;
  52                 if (compare(queue, parent, ix) <= 0)
  53                         break;
  54
  55                 swap(queue, parent, ix);
  56         }
  57 }
  58
  59 void *prio_queue_get(struct prio_queue *queue)
  60 {
  61         void *result;
  62         int ix, child;
  63
  64         if (!queue->nr)
  65                 return NULL;
  66         if (!queue->compare)
  67                 return queue->array[--queue->nr].data; /* LIFO */
  68
  69         result = queue->array[0].data;
  70         if (!--queue->nr)
  71                 return result;
  72
  73         queue->array[0] = queue->array[queue->nr];
  74
  75         /* Push down the one at the root */
  76         for (ix = 0; ix * 2 + 1 < queue->nr; ix = child) {
  77                 child = ix * 2 + 1; /* left */
  78                 if (child + 1 < queue->nr &&
  79                     compare(queue, child, child + 1) >= 0)
  80                         child++; /* use right child */
  81
  82                 if (compare(queue, ix, child) <= 0)
  83                         break;
  84
  85                 swap(queue, child, ix);
  86         }
  87         return result;
  88 }