Andrew's git - gitweb.git/blob

   1#include "cache.h"
   2#include "prio-queue.h"
   3
   4static 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
  13static inline void swap(struct prio_queue *queue, int i, int j)
  14{
  15        SWAP(queue->array[i], queue->array[j]);
  16}
  17
  18void 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
  28void 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
  37void 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
  59void *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}