malloc/dynarray_resize.c

   1 /* Increase the size of a dynamic array.
   2    Copyright (C) 2017-2023 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <dynarray.h>
  20 #include <errno.h>
  21 #include <intprops.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24
  25 bool
  26 __libc_dynarray_resize (struct dynarray_header *list, size_t size,
  27                         void *scratch, size_t element_size)
  28 {
  29   /* The existing allocation provides sufficient room.  */
  30   if (size <= list->allocated)
  31     {
  32       list->used = size;
  33       return true;
  34     }
  35
  36   /* Otherwise, use size as the new allocation size.  The caller is
  37      expected to provide the final size of the array, so there is no
  38      over-allocation here.  */
  39
  40   size_t new_size_bytes;
  41   if (INT_MULTIPLY_WRAPV (size, element_size, &new_size_bytes))
  42     {
  43       /* Overflow.  */
  44       __set_errno (ENOMEM);
  45       return false;
  46     }
  47   void *new_array;
  48   if (list->array == scratch)
  49     {
  50       /* The previous array was not heap-allocated.  */
  51       new_array = malloc (new_size_bytes);
  52       if (new_array != NULL && list->array != NULL)
  53         memcpy (new_array, list->array, list->used * element_size);
  54     }
  55   else
  56     new_array = realloc (list->array, new_size_bytes);
  57   if (new_array == NULL)
  58     return false;
  59   list->array = new_array;
  60   list->allocated = size;
  61   list->used = size;
  62   return true;
  63 }
  64 libc_hidden_def (__libc_dynarray_resize)