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_AND_NULL(queue->array);
  31        queue->nr = 0;
  32        queue->alloc = 0;
  33        queue->insertion_ctr = 0;
  34}
  35
  36void 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
  58void *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}