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        struct prio_queue_entry tmp = queue->array[i];
  16        queue->array[i] = queue->array[j];
  17        queue->array[j] = tmp;
  18}
  19
  20void 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
  30void 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
  39void 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
  61void *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}