malloc/dynarray_resize.c

   1 /* Increase the size of a dynamic array.
   2    Copyright (C) 2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <dynarray.h>
  20 #include <malloc-internal.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23
  24 bool
  25 __libc_dynarray_resize (struct dynarray_header *list, size_t size,
  26                         void *scratch, size_t element_size)
  27 {
  28   /* The existing allocation provides sufficient room.  */
  29   if (size <= list->allocated)
  30     {
  31       list->used = size;
  32       return true;
  33     }
  34
  35   /* Otherwise, use size as the new allocation size.  The caller is
  36      expected to provide the final size of the array, so there is no
  37      over-allocation here.  */
  38
  39   size_t new_size_bytes;
  40   if (check_mul_overflow_size_t (size, element_size, &new_size_bytes))
  41     return false;
  42   void *new_array;
  43   if (list->array == scratch)
  44     {
  45       /* The previous array was not heap-allocated.  */
  46       new_array = malloc (new_size_bytes);
  47       if (new_array != NULL && list->array != NULL)
  48         memcpy (new_array, list->array, list->used * element_size);
  49     }
  50   else
  51     new_array = realloc (list->array, new_size_bytes);
  52   if (new_array == NULL)
  53     return false;
  54   list->array = new_array;
  55   list->allocated = size;
  56   list->used = size;
  57   return true;
  58 }
  59 libc_hidden_def (__libc_dynarray_resize)