prio-queue.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "prio-queue.h"
   4
   5 void prio_queue_reverse(struct prio_queue *queue)
   6 {
   7         int i, j;
   8
   9         if (queue->compare != NULL)
  10                 die("BUG: prio_queue_reverse() on non-LIFO queue");
  11         for (i = 0; i <= (j = (queue->nr - 1) - i); i++) {
  12                 struct commit *swap = queue->array[i];
  13                 queue->array[i] = queue->array[j];
  14                 queue->array[j] = swap;
  15         }
  16 }
  17
  18 void clear_prio_queue(struct prio_queue *queue)
  19 {
  20         free(queue->array);
  21         queue->nr = 0;
  22         queue->alloc = 0;
  23         queue->array = NULL;
  24 }
  25
  26 void prio_queue_put(struct prio_queue *queue, void *thing)
  27 {
  28         prio_queue_compare_fn compare = queue->compare;
  29         int ix, parent;
  30
  31         /* Append at the end */
  32         ALLOC_GROW(queue->array, queue->nr + 1, queue->alloc);
  33         queue->array[queue->nr++] = thing;
  34         if (!compare)
  35                 return; /* LIFO */
  36
  37         /* Bubble up the new one */
  38         for (ix = queue->nr - 1; ix; ix = parent) {
  39                 parent = (ix - 1) / 2;
  40                 if (compare(queue->array[parent], queue->array[ix],
  41                             queue->cb_data) <= 0)
  42                         break;
  43
  44                 thing = queue->array[parent];
  45                 queue->array[parent] = queue->array[ix];
  46                 queue->array[ix] = thing;
  47         }
  48 }
  49
  50 void *prio_queue_get(struct prio_queue *queue)
  51 {
  52         void *result, *swap;
  53         int ix, child;
  54         prio_queue_compare_fn compare = queue->compare;
  55
  56         if (!queue->nr)
  57                 return NULL;
  58         if (!compare)
  59                 return queue->array[--queue->nr]; /* LIFO */
  60
  61         result = queue->array[0];
  62         if (!--queue->nr)
  63                 return result;
  64
  65         queue->array[0] = queue->array[queue->nr];
  66
  67         /* Push down the one at the root */
  68         for (ix = 0; ix * 2 + 1 < queue->nr; ix = child) {
  69                 child = ix * 2 + 1; /* left */
  70                 if ((child + 1 < queue->nr) &&
  71                     (compare(queue->array[child], queue->array[child + 1],
  72                              queue->cb_data) >= 0))
  73                         child++; /* use right child */
  74
  75                 if (compare(queue->array[ix], queue->array[child],
  76                             queue->cb_data) <= 0)
  77                         break;
  78
  79                 swap = queue->array[child];
  80                 queue->array[child] = queue->array[ix];
  81                 queue->array[ix] = swap;
  82         }
  83         return result;
  84 }