prio-queue.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "prio-queue.h"
   4
   5 void clear_prio_queue(struct prio_queue *queue)
   6 {
   7         free(queue->array);
   8         queue->nr = 0;
   9         queue->alloc = 0;
  10         queue->array = NULL;
  11 }
  12
  13 void prio_queue_put(struct prio_queue *queue, void *thing)
  14 {
  15         prio_queue_compare_fn compare = queue->compare;
  16         int ix, parent;
  17
  18         /* Append at the end */
  19         ALLOC_GROW(queue->array, queue->nr + 1, queue->alloc);
  20         queue->array[queue->nr++] = thing;
  21         if (!compare)
  22                 return; /* LIFO */
  23
  24         /* Bubble up the new one */
  25         for (ix = queue->nr - 1; ix; ix = parent) {
  26                 parent = (ix - 1) / 2;
  27                 if (compare(queue->array[parent], queue->array[ix],
  28                             queue->cb_data) <= 0)
  29                         break;
  30
  31                 thing = queue->array[parent];
  32                 queue->array[parent] = queue->array[ix];
  33                 queue->array[ix] = thing;
  34         }
  35 }
  36
  37 void *prio_queue_get(struct prio_queue *queue)
  38 {
  39         void *result, *swap;
  40         int ix, child;
  41         prio_queue_compare_fn compare = queue->compare;
  42
  43         if (!queue->nr)
  44                 return NULL;
  45         if (!compare)
  46                 return queue->array[--queue->nr]; /* LIFO */
  47
  48         result = queue->array[0];
  49         if (!--queue->nr)
  50                 return result;
  51
  52         queue->array[0] = queue->array[queue->nr];
  53
  54         /* Push down the one at the root */
  55         for (ix = 0; ix * 2 + 1 < queue->nr; ix = child) {
  56                 child = ix * 2 + 1; /* left */
  57                 if ((child + 1 < queue->nr) &&
  58                     (compare(queue->array[child], queue->array[child + 1],
  59                              queue->cb_data) >= 0))
  60                         child++; /* use right child */
  61
  62                 if (compare(queue->array[ix], queue->array[child],
  63                             queue->cb_data) <= 0)
  64                         break;
  65
  66                 swap = queue->array[child];
  67                 queue->array[child] = queue->array[ix];
  68                 queue->array[ix] = swap;
  69         }
  70         return result;
  71 }