lib/array.c

   1 /*
   2   unencumbered array.c
   3   dynamic UNORDERED array (yes this got me...)
   4
   5   will grow by allocchunksize (by default 100) when full and
   6   new space is requested.
   7
   8   will shrink by freechunksize (by default 150) if that many
   9   items are not occupied at the end.
  10
  11   clean written from the function prototypes.
  12 */
  13
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include "../core/error.h"
  18
  19 #include "array.h"
  20
  21 void array_init(array *a, unsigned int itemsize) {
  22   a->content = NULL;
  23   a->cursi = 0; /* count */
  24
  25   a->itemsize = itemsize;
  26   a->capacity = 0;
  27
  28   /* allochunksize MUST be <= freechunksize */
  29   a->allocchunksize = 100;
  30   a->freechunksize = 150;
  31 }
  32
  33 /* should be called free_and_reinit really */
  34 void array_free(array *a) {
  35   free(a->content);
  36
  37   array_init(a, a->itemsize);
  38 }
  39
  40 int array_getfreeslot(array *a) {
  41   if(a->cursi + 1 >= a->capacity) {
  42     a->capacity += a->allocchunksize;
  43
  44     /* we can be evil and use the same pointer as we're gonna exit if we fail */
  45     a->content = realloc(a->content, a->capacity * a->itemsize);
  46
  47     if(!a->content)
  48        Error("array", ERR_STOP, "Array resize failed.");
  49   }
  50
  51   return a->cursi++;
  52 }
  53
  54 void array_delslot(array *a, unsigned int index) {
  55   /* if we're not deleting the end item then swap the last item into the deleted items space */
  56   /* unordered so we can do this, and we can also use memcpy */
  57   if(--a->cursi != index)
  58     memcpy((char *)a->content + index * a->itemsize, (char *)a->content + a->cursi * a->itemsize, a->itemsize);
  59
  60   if(a->cursi + a->freechunksize < a->capacity) {
  61
  62     a->capacity = a->cursi + a->allocchunksize;
  63
  64     if(a->capacity == 0) {
  65       free(a->content);
  66
  67       a->content = NULL;
  68     } else {
  69       void *newp = realloc(a->content, a->capacity * a->itemsize);
  70
  71       if(!newp) {
  72         Error("array", ERR_WARNING, "Unable to shrink array!");
  73       } else {
  74         a->content = newp;
  75       }
  76     }
  77   }
  78 }
  79