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         struct prio_queue_entry tmp = queue->array[i];
  16         queue->array[i] = queue->array[j];
  17         queue->array[j] = tmp;
  18 }
  19
  20 void prio_queue_reverse(struct prio_queue *queue)
  21 {
  22         int i, j;
  23
  24         if (queue->compare != NULL)
  25                 die("BUG: prio_queue_reverse() on non-LIFO queue");
  26         for (i = 0; i <= (j = (queue->nr - 1) - i); i++)
  27                 swap(queue, i, j);
  28 }
  29
  30 void clear_prio_queue(struct prio_queue *queue)
  31 {
  32         free(queue->array);
  33         queue->nr = 0;
  34         queue->alloc = 0;
  35         queue->array = NULL;
  36         queue->insertion_ctr = 0;
  37 }
  38
  39 void prio_queue_put(struct prio_queue *queue, void *thing)
  40 {
  41         int ix, parent;
  42
  43         /* Append at the end */
  44         ALLOC_GROW(queue->array, queue->nr + 1, queue->alloc);
  45         queue->array[queue->nr].ctr = queue->insertion_ctr++;
  46         queue->array[queue->nr].data = thing;
  47         queue->nr++;
  48         if (!queue->compare)
  49                 return; /* LIFO */
  50
  51         /* Bubble up the new one */
  52         for (ix = queue->nr - 1; ix; ix = parent) {
  53                 parent = (ix - 1) / 2;
  54                 if (compare(queue, parent, ix) <= 0)
  55                         break;
  56
  57                 swap(queue, parent, ix);
  58         }
  59 }
  60
  61 void *prio_queue_get(struct prio_queue *queue)
  62 {
  63         void *result;
  64         int ix, child;
  65
  66         if (!queue->nr)
  67                 return NULL;
  68         if (!queue->compare)
  69                 return queue->array[--queue->nr].data; /* LIFO */
  70
  71         result = queue->array[0].data;
  72         if (!--queue->nr)
  73                 return result;
  74
  75         queue->array[0] = queue->array[queue->nr];
  76
  77         /* Push down the one at the root */
  78         for (ix = 0; ix * 2 + 1 < queue->nr; ix = child) {
  79                 child = ix * 2 + 1; /* left */
  80                 if (child + 1 < queue->nr &&
  81                     compare(queue, child, child + 1) >= 0)
  82                         child++; /* use right child */
  83
  84                 if (compare(queue, ix, child) <= 0)
  85                         break;
  86
  87                 swap(queue, child, ix);
  88         }
  89         return result;
  90 }