gl/malloc/dynarray_emplace_enlarge.c

   1 /* Increase the size of a dynamic array in preparation of an emplace operation.
   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 #ifndef _LIBC
  20 # include <libc-config.h>
  21 #endif
  22
  23 #include <dynarray.h>
  24 #include <errno.h>
  25 #include <intprops.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28
  29 bool
  30 __libc_dynarray_emplace_enlarge (struct dynarray_header *list,
  31                                  void *scratch, size_t element_size)
  32 {
  33   size_t new_allocated;
  34   if (list->allocated == 0)
  35     {
  36       /* No scratch buffer provided.  Choose a reasonable default
  37          size.  */
  38       if (element_size < 4)
  39         new_allocated = 16;
  40       else if (element_size < 8)
  41         new_allocated = 8;
  42       else
  43         new_allocated = 4;
  44     }
  45   else
  46     /* Increase the allocated size, using an exponential growth
  47        policy.  */
  48     {
  49       new_allocated = list->allocated + list->allocated / 2 + 1;
  50       if (new_allocated <= list->allocated)
  51         {
  52           /* Overflow.  */
  53           __set_errno (ENOMEM);
  54           return false;
  55         }
  56     }
  57
  58   size_t new_size;
  59   if (INT_MULTIPLY_WRAPV (new_allocated, element_size, &new_size))
  60     return false;
  61   void *new_array;
  62   if (list->array == scratch)
  63     {
  64       /* The previous array was not heap-allocated.  */
  65       new_array = malloc (new_size);
  66       if (new_array != NULL && list->array != NULL)
  67         memcpy (new_array, list->array, list->used * element_size);
  68     }
  69   else
  70     new_array = realloc (list->array, new_size);
  71   if (new_array == NULL)
  72     return false;
  73   list->array = new_array;
  74   list->allocated = new_allocated;
  75   return true;
  76 }
  77 libc_hidden_def (__libc_dynarray_emplace_enlarge)