malloc/dynarray_emplace_enlarge.c

   1 /* Increase the size of a dynamic array in preparation of an emplace operation.
   2    Copyright (C) 2017-2024 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_emplace_enlarge (struct dynarray_header *list,
  27                                  void *scratch, size_t element_size)
  28 {
  29   size_t new_allocated;
  30   if (list->allocated == 0)
  31     {
  32       /* No scratch buffer provided.  Choose a reasonable default
  33          size.  */
  34       if (element_size < 4)
  35         new_allocated = 16;
  36       else if (element_size < 8)
  37         new_allocated = 8;
  38       else
  39         new_allocated = 4;
  40     }
  41   else
  42     /* Increase the allocated size, using an exponential growth
  43        policy.  */
  44     {
  45       new_allocated = list->allocated + list->allocated / 2 + 1;
  46       if (new_allocated <= list->allocated)
  47         {
  48           /* Overflow.  */
  49           __set_errno (ENOMEM);
  50           return false;
  51         }
  52     }
  53
  54   size_t new_size;
  55   if (INT_MULTIPLY_WRAPV (new_allocated, element_size, &new_size))
  56     return false;
  57   void *new_array;
  58   if (list->array == scratch)
  59     {
  60       /* The previous array was not heap-allocated.  */
  61       new_array = malloc (new_size);
  62       if (new_array != NULL && list->array != NULL)
  63         memcpy (new_array, list->array, list->used * element_size);
  64     }
  65   else
  66     new_array = realloc (list->array, new_size);
  67   if (new_array == NULL)
  68     return false;
  69   list->array = new_array;
  70   list->allocated = new_allocated;
  71   return true;
  72 }
  73 libc_hidden_def (__libc_dynarray_emplace_enlarge)